Dom-Enalapril Product Monograph

SUMMARY PRODUCT INFORMATION

Each tablet is made with 2.5 mg, 5 mg, 10 mg or 20 mg enalapril maleate that appears as 2 mg, 4 mg, 8 mg or 16 mg enalapril sodium in the tablet.

*The splitting of Dom-ENALAPRIL tablets is not advised.

INDICATIONS AND CLINICAL USE

Dom-ENALAPRIL (enalapril) is indicated for:

• essential or renovascular hypertension
• treatment of symptomatic congestive heart failure

Hypertension

Dom-ENALAPRIL is indicated in the treatment of essential or renovascular hypertension. It is usually administered in association with other drugs, particularly thiazide diuretics.

In using Dom-ENALAPRIL consideration should be given to the risk of angioedema (see WARNINGS AND PRECAUTIONS).

Geriatrics (>65 years of age): See DOSAGE AND ADMINISTRATION.

Pediatrics (<16 years of age): Dom-ENALAPRIL may be used in children (see DOSAGE AND ADMINISTRATION).

Congestive Heart Failure

Dom-ENALAPRIL is indicated in the treatment of symptomatic congestive heart failure usually in combination with diuretics and/or digitalis. In these patients, enalapril improves symptoms, increases survival, and decreases the frequency of hospitalization (see CLINICAL TRIALS for

details and limitations of survival trials). Treatment with enalapril should be initiated under close medical supervision.

In clinically stable asymptomatic patients with left ventricular dysfunction (ejection fraction ≤35%), enalapril decreases the rate of development of overt heart failure and decreases the incidence of hospitalization for heart failure (see CLINICAL TRIALS for details and limitations of survival trials).

CONTRAINDICATIONS

Dom-ENALAPRIL (enalapril) is contraindicated in:

• Patients who are hypersensitive to these products or to any ingredient in their formulation.

  For a complete listing, see the DOSAGE FORMS, COMPOSITION AND PACKAGING section of the product monograph.

• Patients with a history of angioneurotic edema relating to previous treatment with an angiotensin converting enzyme inhibitor.
• Patients with hereditary or idiopathic angioedema.

WARNINGS AND PRECAUTIONS

General

Angioedema: Angioedema of the face, extremities, lips, tongue, glottis and/or larynx has been reported rarely in patients treated with enalapril. This may occur at any time during treatment and may be life threatening.

Very rarely, fatalities have been reported due to angioedema associated with laryngeal edema or tongue edema. Patients with involvement of the tongue, glottis or larynx are likely to experience airway obstruction, especially those with a history of airway surgery. However, where there is involvement of the tongue, glottis or larynx, likely to cause airway obstruction, appropriate therapy which may include subcutaneous adrenaline solution 1:1000 (0.3 mL to 0.5 mL) and/or measures to ensure a patent airway should be administered promptly when indicated.

If angioedema occurs, enalapril should be discontinued promptly and appropriate monitoring should be instituted to ensure complete resolution of symptoms prior to dismissing the patient. Even in those instances where swelling of only the tongue is involved, without respiratory distress, patients may require prolonged observation since this may be life threatening and treatment with antihistamines and corticosteroids may not be sufficient.

Serious Warnings and Precautions

• When used in pregnancy, angiotensin converting enzyme (ACE) inhibitors can cause injury or even death of the developing fetus. When pregnancy is detected, Dom-ENALAPRIL should be discontinued as soon as possible.

In patients who experience angioedema, future administration is contraindicated (see CONTRAINDICATIONS).

The incidence of angioedema during ACE inhibitor therapy has been reported to be higher in black than in non-black patients.

Patients with a history of angioedema unrelated to ACE inhibitor therapy may be at increased risk of angioedema while receiving an ACE inhibitor (see CONTRAINDICATIONS).

Anaphylactoid Reactions during Membrane Exposure: Anaphylactoid reactions have been reported in patients dialysed with high-flux membranes (e.g., polyacrylonitrile [PAN]) and treated concomitantly with an ACE inhibitor. Dialysis should be stopped immediately if symptoms such as nausea, abdominal cramps, burning, angioedema, shortness of breath and severe hypotension occur. Symptoms are not relieved by antihistamines. In these patients consideration should be given to using a different type of dialysis membrane or a different class of antihypertensive agent.

Anaphylactoid Reactions during Desensitization: There have been isolated reports of patients experiencing sustained life-threatening anaphylactoid reactions while receiving ACE inhibitors during desensitizing treatment with hymenoptera (bees, wasp) venom. In the same patients, these reactions have been avoided when ACE inhibitors were temporarily withheld for at least 24 hours, but they have reappeared upon inadvertent rechallenge.

Anaphylactoid Reactions during LDL Apheresis: Rarely, patients receiving ACE inhibitors during low-density lipoprotein (LDL)-apheresis with dextran sulfate have experienced life-threatening anaphylactoid reactions. These reactions were avoided by temporarily withholding ACE inhibitor therapy prior to each apheresis.

Cardiovascular

Hypotension: Symptomatic hypotension has occurred after administration of enalapril, usually after the first or second dose or when the dose was increased. It is more likely to occur in patients who are volume depleted by diuretic therapy, dietary salt restriction, dialysis, diarrhea, or vomiting. In patients with severe congestive heart failure, with or without associated renal insufficiency, excessive hypotension has been observed and may be associated with oliguria and/or progressive azotemia, and rarely with acute renal failure and/or death. Because of the potential fall in blood pressure in these patients, therapy should be started under very close medical supervision, usually in a hospital. Such patients should be followed closely for the first two weeks of treatment and whenever the dose of enalapril and/or diuretic is increased. Similar considerations may apply to patients with ischemic heart or cerebrovascular disease in whom an excessive fall in blood pressure could result in a myocardial infarction or cerebrovascular accident (see ADVERSE REACTIONS).

If hypotension occurs, the patient should be placed in supine position and, if necessary, receive an intravenous infusion of normal saline. A transient hypotensive response is not a contraindication

to further doses which usually can be given without difficulty once the blood pressure has increased after volume expansion.

Valvular Stenosis: There is concern on theoretical grounds that patients with aortic stenosis might be at particular risk of decreased coronary perfusion when treated with vasodilators because they do not develop as much afterload reduction.

Ear/Nose/Throat

Cough: A dry, persistent cough, which usually disappears only after withdrawal or lowering of the dose of enalapril has been reported.

Such possibility should be considered as part of the differential diagnosis of the cough.

Endocrine and Metabolism

Hypoglycemia: Rare cases of hypoglycemia in diabetic patients on oral antidiabetic agents or insulin have been reported. Diabetic patients treated with oral antidiabetic agents or insulin starting an ACE inhibitor should be told to closely monitor for hypoglycemia, especially during the first month of combined use. In addition, hypoglycemia appeared to be more likely to occur during the first weeks of combined treatment and in patients with renal impairment (see ADVERSE REACTIONS).

Hematologic

Neutropenia/Agranulocytosis: Agranulocytosis and bone marrow depression have been caused by angiotensin converting enzyme inhibitors. Several cases of agranulocytosis and neutropenia have been reported in which a causal relationship to enalapril cannot be excluded. Current experience with the drug shows the incidence to be rare. Periodic monitoring of white blood cell counts should be considered, especially in patients with collagen vascular disease and renal disease.

Hepatic/Biliary/Pancreatic

Patients with Impaired Liver Function: Hepatitis, jaundice (hepatocellular and/or cholestatic), elevations of liver enzymes and/or serum bilirubin have occurred during therapy with enalapril in patients with or without pre-existing liver abnormalities (see ADVERSE REACTIONS). In most cases the changes were reversed on discontinuation of the drug.

Should the patient receiving enalapril experience any unexplained symptoms (see CONSUMER INFORMATION), particularly during the first weeks or months of treatment, it is recommended that a full set of liver function tests and any other necessary investigation be carried out. Discontinuation of enalapril should be considered when appropriate.

There are no adequate studies in patients with cirrhosis and/or liver dysfunction. Enalapril should be used with particular caution in patients with pre-existing liver abnormalities. In such patients baseline liver function tests should be obtained before administration of the drug and close monitoring of response and metabolic effects should apply.

Nitritoid Reactions - Gold: Nitritoid reactions (symptoms include facial flushing, nausea, vomiting and symptomatic hypotension) have been reported rarely in patients on therapy with injectable gold (sodium aurothiomalate) and concomitant ACE inhibitor therapy including enalapril (see DRUG INTERACTIONS).

Peri-Operative Considerations

Surgery/Anesthesia: In patients undergoing major surgery or during anesthesia with agents that produce hypotension, enalapril blocks angiotensin II formation, secondary to compensatory renin release. If hypotension occurs and is considered to be due to this mechanism, it can be corrected by volume expansion.

Renal

Renal Impairment: As a consequence of inhibiting the renin-angiotensin-aldosterone system, changes in renal function have been seen in susceptible individuals. In patients whose renal function may depend on the activity of the renin-angiotensin-aldosterone system, such as patients with bilateral renal artery stenosis, unilateral renal artery stenosis to a solitary kidney, or severe congestive heart failure, treatment with agents that inhibit this system has been associated with oliguria, progressive azotemia, and rarely, acute renal failure and/or death. In susceptible patients, concomitant diuretic use may further increase risk.

Use of enalapril should include appropriate assessment of renal function.

Hyperkalemia: Elevated serum potassium (greater than 5.7 mEq/L) was observed in approximately one percent of hypertensive patients in clinical trials with enalapril. In most cases these were isolated values which resolved despite continued therapy. Hyperkalemia was a cause of discontinuation of therapy in 0.28% of hypertensive patients. Risk factors for the development of hyperkalemia include renal insufficiency, diabetes mellitus, and concomitant use of potassium-sparing diuretics (e.g., spironolactone, eplerenone, triamterene, or amiloride), potassium supplements, or potassium-containing salt substitutes. The use of potassium supplements, potassium-sparing diuretics, or potassium-containing salt substitutes particularly in patients with impaired renal function should be given only for documented hypokalemia and with caution and frequent monitoring of serum potassium since they may lead to a significant increase in serum potassium. Hyperkalemia can cause serious, sometimes fatal, arrhythmias. If concomitant use of enalapril and any of the above-mentioned agents is deemed appropriate, they should be used with caution and with frequent monitoring of serum potassium (see DRUG INTERACTIONS, Agents Increasing Serum Potassium).

Special Populations

Pregnant Women: ACE inhibitors can cause fetal and neonatal morbidity and mortality when administered to pregnant women. When pregnancy is detected, enalapril should be discontinued as soon as possible.

The use of ACE inhibitors during the second and third trimesters of pregnancy has been associated with fetal and neonatal injury including hypotension, neonatal skull hypoplasia, anuria, reversible or irreversible renal failure, and death. Oligohydramnios has also been reported,

presumably resulting from decreased fetal renal function, associated with fetal limb contractures, craniofacial deformation, and hypoplastic lung development.

Prematurity, and patent ductus arteriosus and other structural cardiac malformations, as well as neurologic malformations, have also been reported following exposure in the first trimester of pregnancy.

Infants with a history of in utero exposure to ACE inhibitors should be closely observed for hypotension, oliguria, and hyperkalemia. If oliguria occurs, attention should be directed toward support of blood pressure and renal perfusion. Exchange transfusion or dialysis may be required as a means of reversing hypotension and/or substituting for impaired renal function; however, limited experience with those procedures has not been associated with significant clinical benefit.

Enalapril has been removed from the neonatal circulation by peritoneal dialysis with some clinical benefit and may, theoretically, be removed by exchange transfusion, although there is no experience with the latter procedure.

Animal Data

Maternal and fetal toxicity occurred in some rabbits given enalapril at doses of 1 mg/kg/day or more. Saline supplementation prevented the maternal and fetal toxicity seen at doses of 3 and 10 mg/kg/day, but not at 30 mg/kg/day (50 times the maximum human dose). Enalapril was not teratogenic in rabbits.

There was no fetotoxicity or teratogenicity in rats treated with enalapril at doses up to 200 mg/kg/day (333 times the maximum human dose). Fetotoxicity expressed as a decrease in average fetal weight, occurred in rats given 1200 mg/kg/day of enalapril, but did not occur when these animals were supplemented with saline. The drug crosses the placental barrier in rats and hamsters.

Nursing Women: Enalapril and enalaprilat are secreted in human milk in trace amounts. Use of ACE inhibitors (enalapril) is not recommended during breast-feeding.

Pediatrics (<16 years of age): The safety and antihypertensive effect have been studied short-term (one month) in patients aged 6 to 16 years (see DOSAGE AND ADMINISTRATION and ACTION AND CLINICAL PHARMACOLOGY, Pharmacokinetics).

Enalapril is not recommended in neonates and in children with glomerular filtration rate <30 mL/min/1.73 m², as no data are available.

ADVERSE REACTIONS

Adverse Drug Reaction Overview

In controlled clinical trials involving 2314 hypertensive patients and 363 patients with congestive heart failure, the most severe adverse reactions were: angioedema (0.2%), hypotension (2.3%) and renal failure (5 cases).

In hypertensive patients, hypotension occurred in 0.9% and syncope in 0.5%, with a discontinuation rate of 0.1%.

In congestive heart failure patients, hypotension occurred in 4.4% and syncope in 0.8%, with a discontinuation rate of 2.5%.

The most frequent clinical adverse reactions in controlled clinical trials were: headache (4.8%), dizziness (4.6%) and fatigue (2.8%). Discontinuation of therapy was required in 6.0% of the 2677 patients.

Clinical Trial Adverse Drug Reactions – Hypertension

Because clinical trials are conducted under very specific conditions the adverse reaction rates observed in the clinical trials may not reflect the rates observed in practice and should not be compared to the rates in the clinical trials of another drug. Adverse drug reaction information from clinical trials is useful for identifying drug-related adverse events and for approximating rates.

Adverse experiences occurring in greater than one percent of patients with hypertension treated with enalapril in controlled clinical trials are shown below. In patients treated with enalapril, the maximum duration of therapy was three years; in placebo treated patients the maximum duration of therapy was 12 weeks.

Table 1 - Hypertension

Less Common Clinical Trial Adverse Drug Reactions (<1%) – Hypertension Cardiovascular: Hypotension, chest pain, palpitations, acute myocardial infarction Digestive: Vomiting, dysphagia, abdominal pain

Hematologic: Anemia, Leukopenia

Hypersensitivity: Angioedema

Musculoskeletal: Muscle cramps

Nervous System/Psychiatric: Insomnia, nervousness, somnolence, paresthesia Respiratory: Dyspnea

Skin: Pruritus, hyperhidrosis

Special Senses: Taste disturbance

Urogenital: Renal failure, proteinuria, oliguria, impotence

Clinical Trial Adverse Drug Reactions – Heart Failure

Because clinical trials are conducted under very specific conditions the adverse reaction rates observed in the clinical trials may not reflect the rates observed in practice and should not be compared to the rates in the clinical trials of another drug. Adverse drug reaction information from clinical trials is useful for identifying drug-related adverse events and for approximating rates.

Adverse experiences occurring in greater than one percent of patients with heart failure treated with enalapril are shown below. The incidences represent the experiences from both controlled and uncontrolled clinical trials (maximum duration of therapy was approximately one year). In the placebo treated patients, the incidences reported are from the controlled trials (maximum duration of therapy is 12 weeks). The percentage of patients with severe heart failure [New York Heart Association (NYHA) Class IV] was 29 percent and 43 percent for patients treated with enalapril and placebo, respectively.

Table 2 - Congestive Heart Failure

Less Common Clinical Trial Adverse Drug Reactions (<1%) – Heart Failure

Cardiovascular: Palpitations

Musculoskeletal: Muscle cramps

Nervous System/Psychiatric: Insomnia

Skin: Pruritus

Special Senses: Taste disturbance

Urogenital: Renal failure, impotence

Abnormal Hematologic and Clinical Chemistry Findings

Hyperkalemia: (See WARNINGS AND PRECAUTIONS, Renal)

Creatinine, Blood Urea Nitrogen (BUN): Increases in serum creatinine and BUN were reported in about 20% of patients with renovascular hypertension and in about 0.2% of patients with essential hypertension treated with enalapril alone.

In patients with congestive heart failure, who were also receiving diuretics and/or digitalis, increases in BUN and serum creatinine, usually reversible upon discontinuation of enalapril and/or concomitant therapy, were observed in about 9.7% of patients.

Hemoglobin and Hematocrit: Decreases in hemoglobin and hematocrit (mean approximately 0.34 g% and 1.0 vol% respectively) occurred frequently in either hypertensive or congestive heart failure patients treated with enalapril, but were rarely of clinical importance. In clinical trials, less than 0.1% of patients discontinued therapy due to anemia.

Hepatic: Elevations of liver enzymes and/or serum bilirubin have occurred (see WARNINGS AND PRECAUTIONS).

Pediatric Patients: In a four-week placebo-controlled clinical trial, 110 hypertensive pediatric patients (6-16 years of age) received medication for 14 days including 51 patients for a four-week period. The adverse experience profile was no different from that seen in adult patients.

Post-Market Adverse Drug Reactions

Adverse Reactions Reported in Uncontrolled Trials and/or Marketing Experience:

Other serious clinical adverse experiences occurring since the drug was marketed or adverse experiences occurring in 0.5 to 1.0 percent of patients with hypertension or heart failure in clinical trials are listed below and, within each category, are in order of decreasing severity.

Body as a Whole

Anaphylactoid reactions (see WARNINGS AND PRECAUTIONS).

Cardiovascular

Cardiac arrest; myocardial infarction or cerebrovascular accident, possibly secondary to excessive hypotension in high-risk patients (see WARNINGS AND PRECAUTIONS); pulmonary embolism and infarction; pulmonary edema; angina pectoris; arrhythmia including atrial tachycardia and bradycardia; atrial fibrillation; palpitation, Raynaud’s phenomenon.

Endocrine

Syndrome of inappropriate antidiuretic hormone secretion (SIADH)

Digestive

Ileus, pancreatitis, hepatic failure, hepatitis (hepatocellular or cholestatic jaundice), liver function abnormalities (see WARNINGS AND PRECAUTIONS), melena, anorexia, dyspepsia, constipation, glossitis, stomatitis, dry mouth.

Hematologic

Rare cases of neutropenia, thrombocytopenia, hemolytic anemia and bone marrow depression.

Metabolic

Rare cases of hypoglycemia in diabetic patients on oral antidiabetic agents or insulin have been reported (see WARNINGS AND PRECAUTIONS).

Musculoskeletal

Muscle cramps.

Nervous System/Psychiatric

Vertigo, depression, confusion, ataxia, somnolence, insomnia, nervousness, peripheral neuropathy (e.g., paresthesia, dysesthesia), dream abnormality.

Respiratory

Bronchospasm, rhinorrhea, sore throat and hoarseness, asthma, upper respiratory infection, pulmonary infiltrates, eosinophilic pneumonitis.

Skin

Exfoliative dermatitis, toxic epidermal necrolysis, Stevens-Johnson syndrome, pemphigus, herpes zoster, erythema multiforme, urticaria, pruritus, alopecia, flushing, diaphoresis, photosensitivity.

Special Senses

Blurred vision, taste alteration, anosmia, tinnitus, conjunctivitis, dry eyes, tearing, hearing impairment.

Urogenital

Renal failure, oliguria, renal dysfunction (see WARNINGS AND PRECAUTIONS and DOSAGE AND ADMINISTRATION), flank pain, gynecomastia, impotence.

A symptom complex has been reported which may include some or all of the following: fever, serositis, vasculitis, myalgia/myositis, arthralgia/arthritis, a positive antinuclear antibody (ANA), elevated erythrocyte sedimentation rate, eosinophilia and leukocytosis. Rash, photosensitivity or other dermatologic manifestations may occur. These symptoms may be reversible upon discontinuation of therapy.

In very rare cases, intestinal angioedema has been reported with angiotensin converting enzyme inhibitors including enalapril.

Laboratory Test Findings: Hyponatremia

DRUG INTERACTIONS

Drug-Drug Interactions

Hypotension - Patients on Diuretic Therapy: Patients on diuretics and especially those in whom diuretic therapy was recently instituted, may occasionally experience an excessive reduction of blood pressure after initiation of therapy with enalapril. The possibility of hypotensive effects with enalapril can be minimized by either discontinuing the diuretic or increasing the salt intake prior to initiation of treatment with enalapril (see WARNINGS AND PRECAUTIONS and DOSAGE AND ADMINISTRATION).

Agents Increasing Serum Potassium: Since enalapril decreases aldosterone production, elevation of serum potassium may occur. Potassium-sparing diuretics such as spironolactone, eplerenone, triamterene or amiloride, or potassium supplements should be given only for documented hypokalemia and with caution and frequent monitoring of serum potassium particularly in patients with impaired renal function since they may lead to a significant increase in serum potassium. Salt substitutes which contain potassium should also be used with caution (see WARNINGS AND PRECAUTIONS, Hyperkalemia).

Agents Causing Renin Release: The antihypertensive effect of enalapril is augmented by antihypertensive agents that cause renin release (e.g., diuretics).

Agents Affecting Sympathetic Activity: Agents affecting sympathetic activity (e.g., ganglionic blocking agents or adrenergic neuron blocking agents) may be used with caution. Beta-adrenergic blocking drugs add some further antihypertensive effect to enalapril.

Lithium Salts: As with other drugs which eliminate sodium, lithium clearance may be reduced. Therefore, the serum lithium levels should be monitored carefully if lithium salts are to be administered.

Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) Including Selective Cyclooxygenase-2 Inhibitors: The antihypertensive effect of enalapril may be diminished with concomitant non-steroidal anti-inflammatory drug use including selective cyclooxygenase-2 inhibitors (COX-2 inhibitors). In some patients with compromised renal function (e.g., elderly patients or patients who are volume-depleted including those on diuretic therapy) who are being treated with NSAIDs including selective COX-2 inhibitors, the co-administration of ACE inhibitors or angiotensin II receptor antagonists may result in further deterioration of renal function. Cases of acute renal failure, usually reversible, have also been reported. This combination should therefore be administered with caution in this patient population.

Gold: Nitritoid reactions (symptoms include facial flushing, nausea, vomiting and symptomatic hypotension) have been reported rarely in patients on therapy with injectable gold (sodium aurothiomalate) and concomitant ACE inhibitor therapy including enalapril (see WARNINGS AND PRECAUTIONS).

Drug-Food Interactions

The absorption of enalapril is not influenced by the presence of food in the gastrointestinal tract.

DOSAGE AND ADMINISTRATION

Dom-ENALAPRIL for Oral Administration Only

Dosing Considerations

• The absorption of Dom-ENALAPRIL is not affected by food.
• Dosage must be individualized.
• Special attention for dialysis patients.
• The splitting of Dom-ENALAPRIL tablets is not advised.

Recommended Dose and Dosage Adjustment

Hypertension: Initiation of therapy requires consideration of recent antihypertensive drug treatment, the extent of blood pressure elevation and salt restriction; the dosage of other antihypertensive agents being used with enalapril may need to be adjusted.

The recommended initial dose in patients not on diuretics is 5 mg once a day. Dosage should be adjusted according to blood pressure response. The usual dosage range is 10 to 40 mg per day administered in a single dose or two divided doses. In some patients treated once daily, the antihypertensive effect may diminish toward the end of the dosing interval. In such patients, an increase in dosage or twice-daily administration should be considered. If blood pressure is not controlled, a diuretic may be added.

The maximum daily dose is 40 mg. Raising the dose above that level is not recommended because of the possibility of increased adverse reactions.

Symptomatic hypotension occasionally may occur following the initial dose of Dom-ENALAPRIL and is more likely in patients who are currently being treated with a diuretic. The diuretic should, if possible, be discontinued for two to three days before beginning therapy with Dom-ENALAPRIL to reduce the likelihood of hypotension (see WARNINGS AND PRECAUTIONS).

If the diuretic cannot be discontinued, an initial dose of 2.5 mg should be used to determine whether excessive hypotension occurs.

To date there is insufficient experience with Dom-ENALAPRIL in the treatment of accelerated or malignant hypertension. Enalapril, therefore, is not recommended in such situations.

Pediatrics (<16 years of age): The usual recommended starting dose is 0.08 mg/kg (up to 5 mg) once daily. Dosage should be adjusted according to blood pressure response. Doses above 0.58 mg/kg (or in excess of 40 mg) have not been studied in pediatric patients (see ACTION AND CLINICAL PHARMACOLOGY). Dom-ENALAPRIL is not recommended in neonates and in pediatric patients with glomerular filtration rate <30 mL/min/1.73 m², as no data are available.

Geriatrics (>65 years of age): The starting dose should be 2.5 mg. Some elderly patients may be more responsive to Dom-ENALAPRIL than younger patients.

Dosing Adjustment in Renal Impairment: (See WARNINGS AND PRECAUTIONS, Anaphylactoid Reactions during Membrane Exposure)

The doses should be reduced in patients with hypertension according to the following guidelines:

* Enalaprilat is dialyzable. Dosage on nondialysis days should be adjusted depending on the blood pressure response.

Congestive Heart Failure: Enalapril is generally used in conjunction with a diuretic and/or digitalis. Blood pressure and renal function should be monitored, both before and during treatment with Dom-ENALAPRIL, because severe hypotension and, more rarely, consequent renal failure have been reported (see WARNINGS AND PRECAUTIONS).

Initiation of therapy requires consideration of recent diuretic therapy and the possibility of severe salt/volume depletion. If possible, the dose of diuretic should be reduced before beginning treatment to reduce the likelihood of hypotension. Serum potassium also should be monitored (see DRUG INTERACTIONS, Drug-Drug Interactions).

The recommended initial dose in patients with symptomatic heart failure or asymptomatic left ventricular dysfunction (ejection fraction ≤35%) is 2.5 mg once a day, to be administered under close medical supervision to determine the initial effect on blood pressure. After the initial dose, the patient should be observed for at least two hours or until the pressure has stabilized for at least another additional hour (see WARNINGS AND PRECAUTIONS, Hypotension).

In the absence of, or after effective management of symptomatic hypotension following initiation of therapy, the dose should be increased gradually depending on the patient's response. The usual therapeutic dosing range is 5 to 20 mg daily, given as a single dose or two divided doses.

This dose titration may be performed over a 2 to 4 week period, or more rapidly if indicated by the presence of residual signs and symptoms of heart failure. The dosage regimen, in patients with symptomatic heart failure, which was effective in reducing mortality and the need for hospitalization in multicentre studies ranged between 16.4 and 18.8 mg/day. The majority of patient experience in clinical studies has been with twice-daily dosage.

The maximum daily dose is 40 mg.

Dosage Adjustment in Patients with Congestive Heart Failure and Renal Impairment or Hyponatremia: In patients with heart failure who have hyponatremia (serum sodium less than 130 mEq/L) or with serum creatinine greater than 1.6 mg/dL, therapy should be initiated at

2.5 mg daily under close medical supervision (see DOSAGE AND ADMINISTRATION, Congestive Heart Failure and DRUG INTERACTIONS, Drug-Drug Interactions).

The dose may be increased to 2.5 mg b.i.d. then 5 mg b.i.d. and higher as needed, usually at intervals of four days or more if at the time of dosage adjustment there is not excessive hypotension or significant deterioration of renal function.

The maximum daily dose is 40 mg.

OVERDOSAGE

Limited data are available for overdosage in humans. The most prominent features of overdosage reported to date are marked hypotension, beginning some six hours after ingestion of tablets, concomitant with blockade of the renin-angiotensin system, and stupor. Serum enalaprilat levels 100- and 200-fold higher than usually seen after therapeutic doses have been reported after ingestion of 300 mg and 440 mg of enalapril, respectively.

The recommended treatment of overdosage is intravenous infusion of normal saline solution. If ingestion is recent, induce emesis. Enalaprilat may be removed from the general circulation by hemodialysis (see WARNINGS AND PRECAUTIONS, Anaphylactoid Reactions during Membrane Exposure).

ACTION AND CLINICAL PHARMACOLOGY

Mechanism of Action

Enalapril is an ACE inhibitor which is used in the treatment of hypertension and heart failure.

Angiotensin converting enzyme (ACE) is a peptidyl dipeptidase which catalyzes the conversion of angiotensin I to the pressor substance, angiotensin II. After absorption, enalapril, a pro-drug, is hydrolyzed to enalaprilat, its active metabolite, which inhibits ACE. Inhibition of ACE results in decreased plasma angiotensin II, which leads to increased plasma renin activity (due to removal of negative feedback of renin release) and decreased aldosterone secretion. Although the latter decrease is small, it results in a small increase in serum potassium. In patients treated with enalapril and a thiazide diuretic there was essentially no change in serum potassium (see WARNINGS AND PRECAUTIONS).

ACE is identical to kininase II. Thus enalapril may also block the degradation of bradykinin, a potent vasodepressor peptide. However, the role that this plays in the therapeutic effects of either drug is unknown.

While the mechanism through which enalapril lowers blood pressure is believed to be primarily the suppression of the renin-angiotensin-aldosterone system, enalapril also lowers blood pressure in patients with low-renin hypertension.

Pharmacodynamics

Administration of enalapril to patients with hypertension results in a reduction of both supine and standing blood pressure. Abrupt withdrawal of enalapril has not been associated with a rapid increase in blood pressure. In most patients studied, after oral administration of an individual dose of enalapril, the onset of antihypertensive activity is seen at one hour with peak reduction of blood pressure achieved by 4-6 hours. At recommended doses, the antihypertensive effect has been shown to be maintained for at least 24 hours. In some patients the effect may diminish towards the end of the dosing interval (see DOSAGE AND ADMINISTRATION). On occasion, achievement of optimal blood pressure reduction may require several weeks of therapy.

In hemodynamic studies in patients with essential hypertension, blood pressure reduction was accompanied by a reduction in peripheral arterial resistance with an increase in cardiac output and little or no change in heart rate. Following administration of enalapril, there was an increase in renal blood flow; glomerular filtration rate was usually unchanged.

When enalapril is given together with thiazide-type diuretics, its blood pressure lowering effect is approximately additive.

Administration of enalapril to patients with congestive heart failure reduces afterload and preload of the heart, resulting in an increase in cardiac output, without reflex tachycardia.

When used in hypertensive, normolipidemic patients, enalapril had no effect on plasma lipoprotein fractions.

Studies in dogs indicate that enalapril crosses the blood brain barrier poorly, if at all; enalaprilat does not enter the brain.

Pharmacokinetics

Table 3 - Summary of Enalaprilat's Pharmacokinetic Parameters in Healthy Volunteers Further to a 10 mg Oral Dose of Enalapril

* Effective half-life of accumulation.

Absorption: Enalapril is rapidly absorbed with peak serum concentrations of enalapril occurring within one hour. Based on urinary recovery the extent of absorption of enalapril from enalapril is approximately 60%. The absorption of enalapril is not influenced by the presence of food in the gastrointestinal tract.

Metabolism: Following absorption, enalapril is rapidly and extensively hydrolyzed to enalaprilat, a potent angiotensin converting enzyme inhibitor (which itself is poorly absorbed). Peak serum concentrations of enalaprilat occur 3 to 4 hours after an oral dose of enalapril. Except for conversion to enalaprilat, there is no evidence of significant metabolism of enalapril.

Excretion: Excretion of enalapril is primarily renal. Approximately 94% of the dose is recovered in the urine and feces as enalaprilat or enalapril. The principal components in urine are enalaprilat, accounting for about 40% of the dose, and intact enalapril.

The serum concentration profile of enalaprilat exhibits a prolonged terminal phase, apparently associated with binding to ACE. The effective half-life for accumulation of enalaprilat following multiple doses of enalapril is 11 hours.

In hypertensive children aged 2 months to 15 years the kinetics of enalapril were approximately similar to adults (see DOSAGE AND ADMINISTRATION).

Special Populations and Conditions

Pediatrics: In pediatric patients the antihypertensive effect of enalapril has been studied in hypertensive children aged 6 - 16 years (see DOSAGE AND ADMINISTRATION and ACTION AND CLINICAL PHARMACOLOGY, Pharmacokinetics).

Race: The antihypertensive effect of angiotensin converting enzyme inhibitors is generally lower in black than in non-black patients.

Renal Insufficiency: The disposition of enalapril and enalaprilat in patients with renal insufficiency is similar to that in patients with normal renal function until the glomerular filtration rate is 30 mL/min (0.50 mL/s) or less. With renal function ≤30 mL/min (≤0.50 mL/s), peak and trough enalaprilat levels increase, time to peak concentration increases and time to steady state may be delayed. The effective half-life of enalaprilat following multiple doses of enalapril is prolonged at this level of renal insufficiency (see DOSAGE AND ADMINISTRATION). Enalaprilat is dialyzable at the rate of 62 mL/min (1.03 mL/s).

STORAGE AND STABILITY

Store at controlled room temperature (15°C - 30°C). Keep container tightly closed. Protect from moisture.

NOTE: 100 and 500 tablet bottle: discard remaining tablets six months after opening bottle.

DOSAGE FORMS, COMPOSITION AND PACKAGING

Composition

Each tablet of Dom-ENALAPRIL is made with 2.5, 5, 10 and 20 mg of enalapril maleate that appears as 2, 4, 8 or 16 mg of enalapril sodium, respectively in the tablets, and the following non-medicinal ingredients: copovidone, lactose, pregelatinized starch, sodium bicarbonate and zinc stearate. 10 and 20 mg tablets also contain red and/or yellow iron oxides.

Availability of Dosage Forms

Dom-ENALAPRIL 2.5 mg Tablets: Supplied as white, oval-shaped tablet, debossed with “P” letter on one side of the score line and “2.5” on the other side of the score line and nothing on the other side. Available in polyethylene bottles of 100 and 500 tablets.

Dom-ENALAPRIL 5 mg Tablets: Supplied as white, shield-shaped tablet, debossed with “P” letter and “5” on one side and scored on the other side. Available in polyethylene bottles of 100 and 500 tablets.

Dom-ENALAPRIL 10 mg Tablets: Supplied as salmon, shield-shaped tablet, debossed with “P” letter and “10” on one side and scored on the other side. Available in polyethylene bottles of 100 and 500 tablets.

Dom-ENALAPRIL 20 mg Tablets: Supplied as peach, shield-shaped tablet debossed with “P” letter and “20” on one side and scored on the other side. Available in polyethylene bottles of 100 and 500 tablets.

The splitting of Dom-ENALAPRIL tablets is not advised.

PART II: SCIENTIFIC INFORMATION

PHARMACEUTICAL INFORMATION

Drug Substance

CLINICAL TRIALS

Comparative Bioavailability Studies

A randomized two-way crossover, blinded, single-dose comparative bioavailability study was performed in normal healthy non-smoking male volunteers (n=24) under fasting conditions on Enalapril tablets using Dominium Pharmacal. Dom-ENALAPRIL 5 mg tablets versus the reference product, VASOTEC^® 5 mg Tablets, by Merck Frosst Canada Ltd. The pharmacokinetic data calculated for the Dom-ENALAPRIL 5 mg tablets and VASOTEC^® 5 mg tablets formulation are tabulated below. The number of subjects that were included in the PK analysis was 23.

Table 10 - SUMMARY TABLE OF THE COMPARATIVE BIOAVAILABILITY DATA

Enalapril

(1 x 5 mg)

From measured data

Geometric Mean Arithmetic Mean (CV %)

* Dom-ENALAPRIL

† Vasotec® MerckFrosst, Canada; 5 mg tablets were purchased in Canada.

§ Expressed as the median (range) only

€ Expressed as the arithmetic mean (CV%) only

‡ The ratios were calculated using the least square mean differences

A randomized two-way crossover, blinded, single-dose comparative bioavailability study was performed in normal healthy non-smoking male volunteers (n=24) under fasting conditions on Enalapril tablets using Dominium Pharmacal. Dom-ENALAPRIL 20 mg tablets versus the reference product, VASOTEC^® 20 mg Tablets, by Merck Frosst Canada Ltd. The pharmacokinetic data calculated for the Dom-ENALAPRIL 20 mg tablets and VASOTEC^® 20 mg tablets formulation are tabulated below. The number of subjects that were included in the PK analysis was 22.

Table 10 - SUMMARY TABLE OF THE COMPARATIVE BIOAVAILABILITY DATA

* Dom-ENALAPRIL

† Vasotec® MerckFrosst, Canada; 20 mg tablets were purchased in Canada.

§ Expressed as the median (range) only

€ Expressed as the arithmetic mean (CV%) only

‡ The ratios were calculated using the least square mean differences

Study demographics and trial design

Table 4 - Summary of patient demographics for clinical trials

Study results

Table 5 - Results of SOLVD-Treatment study

In a multicentre, placebo-controlled, double-blind study (SOLVD, see REFERENCES, no. 23), 2569 patients with symptomatic heart failure (primarily New York Heart Association Class II and III and ejection fraction ≤35%), were randomized to placebo or enalapril given as an adjunct to conventional therapy. Diseases that excluded patients from enrolment in the study included severe stable angina, hemodynamically significant valvular or outflow tract obstruction, renal failure, cerebral vascular disease (e.g., significant carotid artery diseases), advanced pulmonary disease, malignancies, active myocarditis and constrictive pericarditis. The use of enalapril was associated with an 11% reduction in all-cause mortality (which corresponds to a 16% risk reduction in all-cause mortality) and a 30% reduction in hospitalization for heart failure (which corresponds to a 36% risk reduction in hospitalization for heart failure). The chief difference in mortality was in deaths due to progressive heart failure. There was no significant difference in the number of deaths classified as due to arrhythmia without worsening congestive heart failure.

Study demographics and trial design

Table 6 - Summary of patient demographics for clinical trials

Study results

Table 7 - Results of SOLVD-Prevention study

A second multicentre trial used the SOLVD protocol for a study of asymptomatic or minimally symptomatic patients. SOLVD-Prevention patients, who had left ventricular ejection fraction ≤35% and no history of symptomatic heart failure, were randomized to placebo (n=2117) or enalapril (n=2111) and followed for up to 5 years. The majority of patients in the SOLVD-Prevention trial had a history of ischemic heart disease. A history of myocardial infarction was present in 80% of patients, current angina pectoris in 34%, and a history of hypertension in 37%. No statistically significant mortality effect was demonstrated in this population. Enalapril-treated subjects had 32% fewer first hospitalizations for heart failure, and 32% fewer total heart failure hospitalizations. Compared to placebo, 32% fewer patients receiving enalapril developed symptoms of overt heart failure.

Hospitalizations for cardiovascular reasons were also reduced. There was an insignificant reduction in hospitalizations for any cause in the enalapril treatment group (for enalapril vs. placebo, respectively, 1166 vs. 1201 first hospitalizations, 2649 vs. 2840 total hospitalizations), although the study was not powered to look for such an effect.

The SOLVD-Prevention trial was not designed to determine whether treatment of asymptomatic patients with low ejection fraction would be superior, with respect to preventing hospitalization, to closer follow-up and use of enalapril at the earliest sign of heart failure. However, under the conditions of follow-up in the SOLVD-Prevention trial (every four months at the study clinic; personal physician as needed), 68% of patients on placebo who were hospitalized for heart failure had no prior symptoms recorded which would have signaled initiation of treatment.

The SOLVD-Prevention trial was also not designed to show whether enalapril modified the progression of underlying heart disease.

Study demographics and trial design

Table 8 - Summary of patient demographics for clinical trials

Study results

Table 9 - Results of CONSENSUS study

In another multicentre, placebo-controlled trial (CONSENSUS, see BIBLIOGRAPHY, no. 22), 253 patients with severe congestive heart failure (New York Heart Association Class IV) were randomized to placebo or enalapril given as an adjunct to conventional therapy. The use of enalapril was associated with an improvement of symptoms and a reduction in mortality from the progression of heart failure. No difference was seen in the incidence of sudden cardiac death.

DETAILED PHARMACOLOGY

Mechanism of Action

Effects on Blood Pressure

Other Effects

TOXICOLOGY

Acute Toxicity

LD₅₀ Values:

a Merck Sharp and Dohme Research Laboratories, West Point, PA, USA

b Nippon Merck-Banyu Co., Menuma, Japan

Signs of toxicity: ptosis, decreased activity, bradypnea, loss of righting, ataxia, dyspnea, and clonic convulsions.

Sub-Acute and Chronic Toxicity

Teratology Studies

Fertility and Postnatal Evaluation Studies

Mutagenicity Studies

Enalapril was not mutagenic in the Ames microbial mutagen test with or without metabolic activation, in the Rec-Assay, sister chromatid exchange with cultured chinese hamster cells, (up to 20 mg/mL) and the micro-nucleus test with mice.

In vitro chromosomal aberration test = enalapril was clastogenic at 10 and 20 mg/mL but not at 5 mg/mL.

Carcinogenicity Studies

There was no evidence of a carcinogenic effect when enalapril was administered for 106 weeks to rats (Charles River CD-1) at doses up to 90 mg/kg/day (150 times the maximum daily human dose).

Enalapril has also been administered for 94 weeks to male and female mice (Charles River CD1) at doses up to 90 and 180 mg/kg/day, respectively, (150 and 300 times the maximum daily dose for humans) and no evidence of carcinogenicity was noted.

REFERENCES

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   Biollaz J, Schelling JL, Jacot des Combes B, Brunner DB, Desponds G, Brunner HR.

   Enalapril maleate and a lysine analogue (MK-521) in normal volunteers; relationship between plasma drug levels and the renin angiotensin system. Br J Clin Pharmacol 1982;14:363-8.

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   Biollaz J, Brunner HR, Gavras I, Waeber B, Gavras H. Antihypertensive therapy with

   MK421: Angiotensin II - Renin relationships to evaluate efficacy of converting enzyme blockade. J Cardiovasc Pharmacol 1982;4:966-72.

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   Brunner DB, Desponds G, Biollaz J, Keller I, Ferber F, Gavras H, Brunner HR, Schelling JL.

   Effect of a new angiotensin converting enzyme inhibitor MK-421 and its lysine analogue on the components of the renin system in healthy subjects. Br J Clin Pharmacol 1981;11:461-7.

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   Cleary JP, Taylor JW. Enalapril: a new angiotensin converting enzyme inhibitor. Drug Intell

   Clin Pharm 1986;20(3)177-86.

6. 6. Cleland JGF, Dargie HJ, McAlpine H, Ball SG, Morton JJ, Robertson JIS, Ford I. Severe hypotension after first dose of enalapril in heart failure. Br Med J 1985;291:1309-12.
7. 7. Cody RJ, Covit AB, Schaer GL, Laragh JH. Evaluation of a long-acting converting enzyme inhibitor (enalapril) for the treatment of chronic congestive heart failure. J Am Coll Cardiol 1983;1(4):1154-9.
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   Cohn JN, Johnson G, Ziesche S, Cobb F, Francis G, Tristani F, Smith R, Dunkman WB, Loeb

   H, Wong M, Bhat G, Goldman S, Fletcher RD, Doherty J, Hughes CV, Carson P, Cintron G, Shabetai R, Haakenson C. A comparison of enalapril with hydralazine-isosorbide dinitrate in the treatment of chronic congestive heart failure. N Engl J Med 1991;325:303-10.

9. 9. Gavras H, Biollaz J, Waeber B, Brunner HR, Gavras I, Davies RO. Antihypertensive effect of the new oral angiotensin converting enzyme inhibitor "MK-421". Lancet 1981;ii:543-7.
10. 10. Gomez HJ, Cirillo VJ. Angiotensin converting enzyme inhibitors: The clinical pharmacology of captopril and enalapril maleate. Clinical pharmacology and therapeutics (International Congress Series No. 604), Velasco, M. ed., Excerpta Medica, Amsterdam. 1983;52-7.
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    Hodsman GP, Brown JJ, Davies DL, Fraser R, Lever AF, Morton JJ, Murray GD, Robertson

    JIS. Converting-enzyme inhibitor enalapril (MK-421) in treatment of hypertension with renal artery stenosis. Br Med J 1982;285:1697-9.

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    Hodsman GP, Brown JJ, Cumming AMM, Davies DL, East BW, Lever AF, Morton JJ,

    Murray GD, Robertson JIS. Enalapril (MK-421) in the treatment of hypertension with renal artery stenosis, (Symposium: on the renin-angiotensin-aldosterone system: treatment of hypertension and heart failure, Milan, Italy, 28 May 1983). J Hypertension 1(Suppl. 1)1983;109-17.

13. 13. Ibsen H, Egan B, Osterziel K, Vander A, Julius S. Reflex-hemodynamic adjustments and baroreflex sensitivity during converting enzyme inhibition with MK-421 in normal humans. Hypertension 1983;5 (Suppl. I):184^.91.
14. 14. Larochelle P, Carruthers SG, Krip G. Comparison of monotherapy with enalapril and atenolol in mild to moderate hypertension. Can Med Assoc J 1987;(37):803-8.
15. 15. McNabb WR, Brooks BA, Noormohamed F, Lant AF. The effect of enalapril on serum prolactin. Br J Clin Pharmacol 1983;15:752-4.
16. 16. Millar JA, Derx FHM, McLean K, Reid JL. Pharmacodynamics of converting enzyme inhibition: The cardiovascular, endocrine and autonomic effects of MK-421 (enalapril) and MK-521. Br J Clin Pharmacol 1982;14:347-55.
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    Congestive Heart Failure; ed. Braunwald E, Mock M, Watson J. Grune & Stratton.

18. 18. Packer M, Hung Lee W, Yushak M, Medina N. Comparison of captopril and enalapril in patients with severe chronic heart failure. N Engl J Med 1986;315:847-53.
19. 19. Packer M, Hung Lee W, Medina N, Yushak M, Kessler PD. Functional renal insufficiency during long-term therapy with captopril and enalapril in severe chronic heart failure. Ann Intern Med 1987;106(3):346-54.
20. 20. Packer M, ed. Do vasodilators prolong life in heart failure? N Engl J Med 1987;316:1471-73.
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    Turini GA, Waeber B, Brunner HR. The rennin-angiotensin system in refractory heart failure:

    Clinical, hemodynamic and hormonal effects of captopril and enalapril. Eur Heart J 1983;4:189-97.

22. 22. The CONSENSUS Trial Study Group. Effects of enalapril on mortality in severe congestive heart failure. Results of the Cooperative North Scandinavian Enalapril Survival Study (CONSENSUS). N Engl J Med 1987;316:1429-35.
23. 23. The SOLVD Investigators. Effect of enalapril on survival in patients with reduced left ventricular ejection fractions and congestive heart failure. N Engl J Med 1991;325:293-302.
24. 24. The SOLVD Investigators. Effect of enalapril on mortality and the development of heart failure in asymptomatic patients with reduced left ventricular ejection fractions. N Engl J Med 1992;327:685-91.
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    Wilkins LH, Dustan HP, Walker JF, Oparil S. Enalapril in low-renin essential hypertension.

    Clin Pharmacol Ther 1983;34(3):297-302.

26. 26. Product Monograph : VASOTEC^®, Merck Frosst Canada Ltd., Control No. 116570, Revision dated December 15, 2009;