Doxazosin-1: Uses, Side Effects and Dosage

ABOUT THIS MEDICATION

What the medication is used for:

Your doctor has prescribed DOXAZOSIN because you either have a medical condition called benign prostatic hyperplasia (BPH) or Hypertension. This leaflet describes DOXAZOSIN as a treatment for BPH.

What it BPH?

BPH is an enlargement of the prostate gland. After age 50, most men develop enlarged prostates. The prostate is located below the bladder and surrounds the urethra which is a tube that drains urine from the bladder. The symptoms of BPH, however, can be caused by an increase in the tightness of muscles in the prostate. If the muscles inside the prostate tighten, they can squeeze the urethra and slow the flow of urine. This can lead to symptoms such as:

• weak or interrupted urinary stream
• sensation that you cannot completely empty your bladder
• sensation of delay or hesitation when you start to urinate
• need to urinate often, especially at night, or
• sensation that you must urinate immediately.

Hypertension is the medical term for high blood pressure (HBP). When blood flows through the blood vessels, it pushes against their walls, almost like water pushing against the sides of a hose. Blood pressure is like that “push”. When blood pressure is high (like the water pressure in a hose when the nozzle is partially shut), damage can occur to the heart and blood vessels.

Although you may not feel any symptoms for years, hypertension can lead to stroke, heart attack, kidney disease and other serious conditions.

What it does:

DOXAZOSIN blocks smooth muscle receptors of the bladder neck and the prostate called alpha1-adrenoceptors. This blockade causes the smooth muscles of the bladder neck and prostate to relax and decreases muscle tone. This can lead to a rapid improvement in urine flow and symptoms within 1 to 2 weeks period. However, not all patients respond in the same way, and since each case of BPH is different, you should keep in mind the following:

• Prior to treatment with DOXAZOSIN, you should have a thorough urological evaluation to determine the severity of your condition, and to exclude the need for immediate surgery or the possibility of carcinoma of the prostate.
• Even if taking DOXAZOSIN helps your condition, it is not known whether DOXAZOSIN reduces the need for surgery.
• DOXAZOSIN will not cure your benign prostatic hyperplasia (BPH). DOXAZOSIN will make your urine flow better and improve the symptoms of BPH. In some patients, bothersome adverse effects may occur as a result of the DOXAZOSIN therapy.

Similarly, DOXAZOSIN lowers blood pressure by relaxing the blood vessels so that blood can flow more easily through the body.

When it should not be used:

DOXAZOSIN should not be used if you have a known allergy to DOXAZOSIN (doxazosin mesylate) or any of the non-medicinal ingredients (see list below).

It is also contraindicated in patients with a known sensitivity to quinazoline (such as prazosin and tetrazosin)

What the medicinal ingredient is:

doxazosin mesylate

What the non-medicinal ingredients are:

Lactose, magnesium stearate, microcrystalline cellulose, sodium lauryl sulfate and sodium starch glycolate.

What dosage forms it comes in:

Tablets: 1 mg, 2 mg, and 4 mg (doxazosin)

WARNINGS AND PRECAUTIONS

BEFORE you use DOXAZOSIN talk to your doctor or pharmacist if:

• You take phosphodiesterase (PDE-5)-inhibitor such as

  sildenafil, tadalafil or vardenafil, due to the risk of developing low blood pressure.

• you take other medications, including those you can buy

  without prescription and herbal products, or if you drink alcohol;

• you have or have had heart or blood vessel diseases;
• you have heart problems;
• you have or have had kidney and liver disease;
• you have or have had stomach or intestinal problems;

• you suffer from muscular dystrophy or other neuromuscular

  disorder;

• You are pregnant or plan to get pregnant;

• Your are breastfeeding or plan to breastfeed.

DOXAZOSIN can cause a sudden drop in blood pressure after the first dose or first few doses. You may feel dizzy, faint, or "light-headed", particularly after you get up from bed or from a chair. This is more likely to occur after you have taken the first few doses, but can occur at any time while you are taking the drug. It can also occur if you stop taking the drug and then restart treatment. If you feel very dizzy, faint or "light-headed" you should contact your doctor. Your doctor will discuss with you how often you need to visit and how often your blood pressure should be checked.

In general, you should be cautious when using a phosphodiesterase (PDE-5) inhibitor such as sildenafil, tadalafil or vardenafil when taking DOXAZOSIN due to the risks of developing serious hypotension (low blood pressure).

Your doctor has prescribed DOXAZOSIN for symptomatic BPH or High blood pressure and not for prostatic cancer. It is possible for men to have both BPH and prostate cancer at the same time. Doctors usually recommend that men be checked for prostate cancer once a year when they turn 50 (or 40 if a family member has had prostate cancer). These checks should continue while you are taking DOXAZOSIN. DOXAZOSIN is not a treatment for prostate cancer.

About Prostate Specific Antigen (PSA). Your doctor may have done a blood test called PSA. Your doctor is aware that DOXAZOSIN does not affect PSA levels. You may want to ask your doctor more about this if you have a PSA test done.

You should see an effect on your symptoms in 1 to 2 weeks. While taking DOXAZOSIN, you must have regular check-ups to evaluate your progress regarding your BPH and to monitor your blood pressure. Follow your doctor's advice about when to have these check-ups.

If you drink alcohol the effects of the alcohol may be increased and prolonged. You should be aware of that and be more cautious with alcohol or you may wish to avoid alcohol altogether.

If you’re seeing more than one doctor make sure that each one knows about all the medicines you are taking.

INTERACTIONS WITH THIS MEDICATION

The following list includes drugs that may interact with DOXAZOSIN:

• drugs to treat erectile dysfunction (sildenafil, tadalafil, vardenafil)
• drugs to treat hypertension, including diuretics (“water pills”) and other classes of medications

Talk to your doctor or pharmacist if you drink alcohol.

PROPER USE OF THIS MEDICATION

Follow your doctor's instructions very carefully about how to take DOXAZOSIN.

For the treatment of Hypertension:

Usual Adult Dose: Start with 1 mg once daily.

Maximum recommended daily dose is 16 mg once daily.

For the treatment of Benign Prostatic Hyperplasia:

Usual Adult Dose: Start with 1 mg once daily.

Maximum recommended daily dose is 8 mg once daily.

Dose increase should be done gradually with caution due to consideration of possible dizziness/vertigo effect.

Do not share DOXAZOSIN with anyone else; it was prescribed only for you.

Notify your doctor about any illness which may develop during your treatment with DOXAZOSIN and about any new prescription or non-prescription medication you may take. If you require medical help for other reasons, inform the attending physician that you are taking DOXAZOSIN.

You can take DOXAZOSIN either in the morning or at bedtime, with or without food. If you take DOXAZOSIN at bedtime but need to get up from bed to go to the bathroom, get up slowly and cautiously until you are sure how the medication affects you. It is important to get up slowly from a chair or bed at any time until you learn how you react to DOXAZOSIN. You should not

drive or do any hazardous tasks until you are used to the effects of the medication. If you begin to feel dizzy, sit or lie down until you feel better.

If you miss a dose: Talk with your doctor if you don't take it for a few days for some reason; you may then need to restart the medication at a 1 mg dose, increase your dose gradually and again be cautious about possible dizziness.

How long to take DOXAZOSIN: You should take DOXAZOSIN as long as your doctor thinks it is necessary.

Overdose:

If you take too many tablets by accident, call a poison control center immediately.

In case of drug overdose, contact a health care practitioner, hospital emergency department or regional Poison Control Center immediately, even if there are no symptoms.

SIDE EFFECTS AND WHAT TO DO ABOUT THEM

Like all medications, some patients may experience side effects with DOXAZOSIN.

Side effects you could have while taking DOXAZOSIN include drowsiness, fatigue (tiredness), swelling of the feet, shortness of breath, weight gain, headache, and a decrease in your white blood cell count.

You may also experience dry or reduced or other kinds of ejaculation disorders. This condition may be harmless but can lead to temporary infertility during the medication usage.

Most side effects are mild. Discuss any unexpected effects you notice with your doctor.

SERIOUS SIDE EFFECTS, HOW OFTEN THEY HAPPEN AND WHAT TO DO ABOUT THEM

Extremely rarely, doxazosin mesylate and similar medications have caused painful erection of the penis, sustained for hours and unrelieved by sexual intercourse or masturbation. This condition is serious, and if untreated it can be followed by permanent inability to have an erection. If you have a prolonged abnormal erection, call your doctor, or go to an emergency room as soon as possible.

If you notice any of the following potentially serious side effects, please stop taking DOXAZOSIN and contact your doctor immediately:

This is not a complete list of side effects. For any unexpected effects while taking DOXAZOSIN, contact your doctor or pharmacist.

HOW TO STORE IT

Store between 15°C and 30°C.

Keep out of sight and reach of children.

REPORTING SUSPECTED SIDE EFFECTS

You can report any suspected adverse reactions associated with the use of health products to the Canada Vigilance Program by one of the following 3 ways:

• Report online at www.healthcanada.gc.ca/medeffect
• Call toll-free at 1-866-234-2345

• Complete a Canada Vigilance Reporting Form and:

  • Fax toll-free to 1-866-678-6789, or

  • Mail to: Canada Vigilance Program Health Canada

    Postal Locator 0701E

    Ottawa, Ontario

    K1A 0K9

Postage paid labels, Canada Vigilance Reporting Form and the adverse reaction reporting guidelines are available on the MedEffect^™ Canada Web site at www.healthcanada.gc.ca/medeffect.

NOTE: Should you require information related to the management of side effects, contact your health professional. The Canada Vigilance Program does not provide medical advice.

MORE INFORMATION

This document plus the full product monograph, prepared for health professionals, can be obtained by contacting Pro Doc Ltée at 1-800-361-8559, www.prodoc.qc.ca or info@prodoc.qc.ca.

Pro Doc Ltée, Laval, Québec, H7L 3W9

Last revised: October 6, 2014