Orb-Cefuroxime Product Monograph

Actions and Clinical Pharmacology

Cefuroxime axetil is an orally active prodrug of cefuroxime. After oral administration, cefuroxime axetil is absorbed from the gastrointestinal tract and rapidly hydrolyzed by nonspecific esterases in the intestinal mucosa and blood to release cefuroxime into the blood stream. Conversion to cefuroxime, the microbiologically active form, occurs rapidly. The inherent properties of cefuroxime are unaltered after its administration as cefuroxime axetil. Cefuroxime exerts its bactericidal effect by binding to an enzyme or enzymes referred to as penicillin-binding proteins (PBPs) involved in bacterial cell wall synthesis.

This binding results in inhibition of bacterial cell wall synthesis and subsequent cell death. Specifically, cefuroxime shows high affinity for PBP 3, a primary target for cefuroxime in gram-negative organisms such as E. coli.

Comparative Bioavailability Studies

A two-way crossover, randomized, blinded, single-dose bioequivalence study was performed on 22 normal, healthy, non-smoking male subjects under fasting conditions. The rate and extent of absorption of cefuroxime axetil was measured and compared following a single oral dose (1 x 500 mg tablet) of ORB-CEFUROXIME (cefuroxime axetil) or CEFTIN® tablets. The results from measured data are summarized in the table on the following page:

^† Ceftin^® 500 mg Tablets (manufactured by GlaxoSmithKline Inc., Canada) were purchased in Canada. ^§ Expressed as the median (range)

^€ Expressed as the arithmetic mean (CV%)

^# Based on least-square mean estimates.

Indications and Clinical Uses

ORB-CEFUROXIME (cefuroxime axetil) is indicated for the treatment of patients with mild to moderately severe infections caused by susceptible strains of the designated organisms in the following diseases:

Upper Respiratory Tract Infections

Pharyngitis and tonsillitis caused by Streptococcus pyogenes.

Otitis Media caused by Streptococcus pneumoniae, Streptococcus pyogenes (group A beta-hemolytic streptococci), Haemophilus influenzae (beta-lactamase negative and beta-lactamase positive strains) or Moraxella catarrhalis. Sinusitis caused by Moraxella catarrhalis, Streptococcus pneumoniae or Haemophilus influenzae (including ampicillin-resistant strains).

Lower Respiratory Tract Infections

Pneumonia or bronchitis caused by Streptococcus pneumoniae, Haemophilus influenzae (including ampicillin-resistant strains), Haemophilus parainfluenzae, Klebsiella pneumoniae or Moraxella catarrhalis.

Skin Structure Infections

Skin structure infections caused by Staphylococcus aureus, Streptococcus pyogenes or Streptococcus agalactiae.

Gonorrhea

Acute uncomplicated urethritis and cervicitis caused by Neisseria gonorrheae.

Bacteriologic studies to determine the causative organism and its susceptibility to cefuroxime should be performed. Once these results become available antibiotic treatment should be adjusted if required.

Contraindications

ORB-CEFUROXIME (cefuroxime axetil) is contraindicated for patients who have shown Type 1 hypersensitivity to cefuroxime, to any of its components, or to any of the cephalosporin group of antibiotics.

Warnings

Before therapy with ORB-CEFUROXIME (cefuroxime axetil) is instituted, careful inquiry should be made to determine whether the patient has had previous hypersensitivity reactions to cefuroxime, cephalosporins, penicillin, or other drugs. ORB-CEFUROXIME should be administered with caution to any patient who has demonstrated some form of allergy, particularly to drugs. There is some clinical and laboratory evidence of partial cross-allergenicity of the cephalosporins and penicillin. Special care is indicated in patients who have experienced anaphylactic reaction to penicillins or other beta-lactams. If an allergic reaction to ORB-CEFUROXIME occurs, treatment should be discontinued and standard agents (e.g. epinephrine, antihistamines, corticosteroids) administered as necessary.

Pseudomembranous colitis has been reported to be associated with the use of cefuroxime axetil and other broad-spectrum antibiotics. Therefore, it is important to consider its diagnosis in patients administered ORB-CEFUROXIME who develop diarrhea. Treatment with broad spectrum antibiotics, including ORB-CEFUROXIME, alters the normal flora of the colon and may permit overgrowth of Clostridia. Studies indicate that a toxin produced by Clostridium difficile is one primary cause of antibiotic associated colitis. Mild cases of colitis may respond to drug discontinuance alone. Moderate to severe cases should be managed with fluid, electrolyte, and protein supplementation as indicated. When the colitis is severe or not relieved by discontinuance of ORB-CEFUROXIME administration, consideration should be given to the administration of oral vancomycin or other suitable therapy. Other possible causes of colitis should also be considered.

Precautions General

Broad-spectrum antibiotics including ORB-CEFUROXIME (cefuroxime axetil) should be administered with caution to individuals with a history of gastrointestinal disease, particularly colitis.

The concomitant administration of aminoglycosides and some cephalosporins has caused nephrotoxicity. There is no evidence that cefuroxime axetil, when administered alone, is nephrotoxic, although transient elevations of BUN and serum creatinine have been observed in clinical studies. However, the effect of administering cefuroxime axetil concomitantly with aminoglycosides is not known.

Studies suggest that the concomitant use of potent diuretics, such as furosemide and ethacrynic acid, may increase the risk of renal toxicity with cephalosporins.

As with other antibiotics, use of ORB-CEFUROXIME may result in the overgrowth of Candida. Prolonged used may also result in the overgrowth of other non-susceptible organisms (e.g. enterococci and Clostridium difficile), which may require interruption of treatment. Repeated evaluation of the patient's condition is essential. If superinfection occurs during therapy, appropriate measures should be taken. Should an organism become resistant during antibiotic therapy, ORB-CEFUROXIME should be discontinued and another appropriate antibiotic should be substituted.

Pregnancy

The safety of cefuroxime axetil in pregnancy has not been established. The use of ORB-CEFUROXIME in pregnant women requires that the likely benefit from the drug be weighed against the possible risk to the mother and fetus. Animal studies following parenteral administration have shown cefuroxime to affect bone calcification in the fetus and to cause maternal toxicity in the rabbit. Reproduction studies that have been performed in mice and rats at oral doses of up to 50 to 160 times the human dose have revealed no evidence of impaired fertility or harm to the fetus due to cefuroxime axetil. There are, however, no adequate and well-controlled studies in pregnant women. Because animal reproduction studies are not always predictive of human response, this drug should be used during pregnancy only if clearly needed.

Nursing Mothers

Since cefuroxime is excreted in human milk, consideration should be given to discontinuing nursing temporarily during treatment with ORB-CEFUROXIME.

Drug Interactions

Drugs which reduce gastric acidity may result in a lower bioavailability of ORB-CEFUROXIME compared with that of the fasting state and tend to cancel the effect of enhanced post-prandial absorption. In common with other antibiotics, cefuroxime axetil may affect the gut flora, leading to lower estrogen reabsorption and reduced efficacy of combined oral contraceptives.

Drug-Laboratory Test Interactions

A false-positive reaction for glucose in the urine may occur with copper reduction tests (Benedict's or Fehling's solution or with Clinitest^® Tablets) but not with enzyme-based tests for glycosuria (e.g. Clinistix^®, Tes-Tape^®). As a false-negative result may occur in the ferricyanide test, it is recommended that either the glucose oxidase or hexokinase method be used to determine blood plasma glucose levels in patients receiving ORB-CEFUROXIME.

Cefuroxime does not interfere with the assay of serum and urine creatinine by the alkaline picrate method.

Cephalosporins as a class tend to be absorbed onto the surface of red cell membranes and react with antibodies directed against the drug to produce a positive Coombs’ test (which can interfere with cross-matching of blood) and very rarely hemolytic anemia.

Ability to Perform Tasks That Require Judgement, Motor or Cognitive Skills As this medicine may cause dizziness, patients should be warned to be cautious when driving or operating machinery.

Adverse Reactions

The following adverse reactions have been reported:

Gastrointestinal (approximately 8% of patients): Diarrhea (5.6%), nausea (2.4%), vomiting (2.0%), loose stools (1.3%). Reports of abdominal pain have occurred.

Hepatic (3% of patients): Transient increases of hepatic enzyme levels [ALT (SGPT), AST (SGOT), LDH].

Central Nervous System (2.2% of patients): Headache and dizziness.

Hypersensitivity (1.3% of patients): Rashes (0.6%), pruritus (0.3%), urticaria (0.2%), shortness of breath and rare reports of bronchospasm. Hypersensitivity reactions to cefuroxime axetil may occur in patients who report delayed hypersensitivity to penicillins (see WARNINGS). As with other cephalosporins, there have been rare reports of drug fever.

Hematologic: increased erythrocyte sedimentation rate, eosinophilia, decreased hemoglobin and very rarely hemolytic anemia.

Miscellaneous: The following adverse reactions have been observed to occur, although infrequently, in association with parenteral cefuroxime sodium and may be potential adverse effects of oral cefuroxime axetil: drowsiness, vaginitis, positive direct Coombs test, and transient increases in serum bilirubin, creatinine, alkaline phosphatase, and urea nitrogen (BUN).

POSTMARKETING EXPERIENCE WITH CEFUROXIME AXETIL

In addition to adverse events reported during clinical trials, the following events have been identified during clinical practice in patients treated with cefuroxime axetil tablets or with cefuroxime axetil oral suspension and were reported spontaneously. Data are generally insufficient to allow an estimate of incidence or to establish causation.

General: The following hypersensitivity reactions have been reported: anaphylaxis, angioedema, pruritus, rash, serum sickness-like reaction, urticaria.

Gastrointestinal: Pseudomembranous colitis (see WARNINGS).

Hematologic: Thrombocytopenia, and leucopenia (sometimes profound).

Hepatic: Jaundice (predominantly cholestatic) and hepatitis have been reported very rarely.

Infections and Infestations: Candida overgrowth.

Neurologic: Seizure.

Skin: Erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis.

Urologic: Renal dysfunction.

Symptoms and Treatment of Overdosage

Other than general supportive treatment, no specific antidote is known. Excessive serum levels of cefuroxime can be reduced by dialysis. For treatment of hypersensitive reactions, See WARNINGS. For management of a suspected drug overdose, contact your Regional Poison Control centre.

Dosage and Administration

ORB-CEFUROXIME (cefuroxime axetil) may be given orally without regard to meals. Absorption is enhanced when ORB-CEFUROXIME is administered with food.

DOSAGE

ORB-CEFUROXIME TABLETS

Adults and Children 12 Years of Age and Older:

The usual recommended dosage is 250 mg twice a day. However, dosage may be modified according to the type of infection present as indicated below:

TYPE OF INFECTION DOSAGE

pharyngitis, tonsillitis, sinusitis, bronchitis,

skin structure infections 250 mg twice daily more severe infections eg. pneumonia 500 mg twice daily

Uncomplicated gonorrhea 1000 mg single dose

There is presently no data available on the effects of cefuroxime axetil in patients with renal impairment. However, in patients where there is significant impairment, a reduction in ORB-CEFUROXIME dosage may be required.

Infants and Children less than 12 Years of Age:

ORB-CEFUROXIME tablets are not recommended for infants and children less than 12 years of age.

The usual duration of treatment for ORB-CEFUROXIME Tablets is 7 to 10 days. For β-hemolytic streptococcal infections, therapy should be continued for at least 10 days.

Pharmaceutical Information

Drug Substance

Proper Name: cefuroxime axetil

Chemical Name: “(RS)-1-Hydroxyethyl (6R,7R)-7-[2-(2-furyl)glyoxylamido]-3-

(hydroxymethyl)-8-oxo-5-azabicyclo[4,2,0]oct-2-ene-2-carboxylate, 72-(Z)-(O-methyloxime), 1-acetate-3-carbamate.”

Structural Formula:

Molecular Formula: C₂₀H₂₂N₄O₁₀S

Molecular Weight: 510.5

Description: Cefuroxime axetil is an amorphous white to cream-colored powder. It is soluble in dimethyl sulfoxide, dimethylformamide, 1, 4-dioxan, chloroform, acetone, glacial acetic acid, ethyl acetate, and methanol. It is soluble with decomposition in 2N sodium hydroxide and slightly soluble in water, diethyl ether, 95% ethanol, and toluene, and insoluble in 2N hydrochloric acid. Cefuroxime axetil decomposes below its melting point.

Composition

ORB-CEFUROXIME (cefuroxime axetil) Tablets are available in two strengths which contain 250 mg and 500 mg of cefuroxime (as cefuroxime axetil).

Each ORB-CEFUROXIME Tablet contains the following excipients: mannitol, citric acid anhydrous, crospovidone XL, talc, sodium lauril sulphate, sodium hydrogen carbonate, colloidal anhydrous silica, povidone, titanium dioxide, docusate sodium, and propylene glycol.

Storage

Store tablets between 15°C and 30°C. Keep in original container. Store dry and at room temperature.