Consumer Drug Information

prazosin

Generic Name: prazosin (PRA zoe sin)
Brand Names: Minipress

What is prazosin?

Prazosin is in a group of drugs called alpha-adrenergic blockers. Prazosin causes the blood vessels (veins and arteries) to relax and expand, improving blood flow. Prazosin also relaxes muscles in the prostate and bladder neck, making it easier to urinate.

Prazosin is used to treat hypertension (high blood pressure).

Prazosin may also be used for other purposes not listed in this medication guide.

What is the most important information I should know about prazosin?

You should not use this medication if you are allergic to prazosin. Prazosin may cause dizziness or fainting, especially when you first start taking it or when you start taking it again. Be careful if you drive or do anything that requires you to be alert. Avoid standing for long periods of time or becoming overheated during exercise and in hot weather. Avoid getting up too fast from a sitting or lying position, or you may feel dizzy. Call your doctor if you have severe dizziness or feel like you might pass out.

Some things can cause your blood pressure to get too low. This includes vomiting, diarrhea, heavy sweating, heart disease, dialysis, a low-salt diet, or taking other diuretics (water pills). Tell your doctor if you have a prolonged illness that causes diarrhea or vomiting.

Avoid drinking alcohol. It can increase some of the side effects of prazosin.

To be sure prazosin is helping your condition, your blood pressure will need to be checked on a regular basis. Your doctor will also need to check your progress. Do not miss any scheduled appointments.

Keep using this medicine as directed, even if you feel well. High blood pressure often has no symptoms. You may need to use blood pressure medication for the rest of your life.

What should I discuss with my healthcare provider before taking prazosin?

You should not use this medication if you are allergic to prazosin.

Prazosin can affect the pupils of your eyes during cataract surgery. If you have cataract surgery during your treatment with prazosin, tell the surgeon ahead of time that you take prazosin. Do not stop using the medication before surgery unless your surgeon tells you to.

FDA pregnancy category C. It is not known whether prazosin is harmful to an unborn baby. Before taking this medication, tell your doctor if you are pregnant or plan to become pregnant during treatment. Prazosin can pass into breast milk and may harm a nursing baby. Do not use this medication without telling your doctor if you are breast-feeding a baby.

How should I take prazosin?

Take this medication exactly as it was prescribed for you. Do not take the medication in larger amounts, or take it for longer than recommended by your doctor. Follow the directions on your prescription label.

Take each dose with a full glass of water. Prazosin lowers blood pressure and may cause dizziness or fainting, especially when you first start taking it, or when you start taking it again. Call your doctor if you have severe dizziness or feel like you might pass out.

To be sure this medication is helping your condition, your blood pressure will need to be checked on a regular basis. Your doctor will also need to check your progress. Do not miss any scheduled appointments.

Keep using this medicine as directed, even if you feel well. High blood pressure often has no symptoms. You may need to use blood pressure medication for the rest of your life.

Store prazosin at room temperature away from moisture and heat.

What happens if I miss a dose?

Take the missed dose as soon as you remember. If it is almost time for your next dose, skip the missed dose and take the medicine at the next regularly scheduled time. Do not take extra medicine to make up the missed dose.

If you miss doses for several days in a row, call your doctor before taking any additional doses. You may need to use a lower dose of prazosin for a short time.

What happens if I overdose?

Seek emergency medical attention if you think you have used too much of this medicine.

Overdose symptoms may include extreme drowsiness or fainting.

What should I avoid while taking prazosin?

Prazosin can cause side effects that may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be awake and alert.

To prevent dizziness, avoid standing for long periods of time or becoming overheated during exercise and in hot weather.

Avoid getting up too fast from a sitting or lying position, or you may feel dizzy. Get up slowly and steady yourself to prevent a fall.

Avoid drinking alcohol. It can increase some of the side effects of prazosin.

Prazosin side effects

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat. Call your doctor at once if you have any of these serious side effects:

fast or pounding heartbeats;
feeling like you might pass out;
feeling short of breath;
swelling in your hands, ankles, or feet; or
penis erection that is painful or lasts 4 hours or longer.

Less serious side effects may include:

drowsiness, dizziness, spinning sensation;
weakness, tired feeling;
headache;
nausea, vomiting, constipation, diarrhea;
numbness or tingly feeling;
stuffy nose, dry mouth; or
blurred vision.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Prazosin Dosing Information

Usual Adult Dose for Congestive Heart Failure:

Initial dose: 1 mg orally 2-3 times a day.
Maintenance dose: 6-15 mg daily given in divided doses.

Usual Adult Dose for Hypertension:

Initial dose: 1 mg orally 2-3 times a day.
Maintenance dose: 6-15 mg daily given in divided doses.

Usual Adult Dose for Benign Prostatic Hyperplasia:

Initial dose: 1 mg orally 2-3 times a day.
Maintenance dose: 6-15 mg daily given in divided doses.

What other drugs will affect prazosin?

The following drugs can interact with prazosin. Tell your doctor if you are using any of these:

digoxin (digitalis, Lanoxin);
sildenafil (Viagra, Revatio);
tadalafil (Cialis);
vardenafil (Levitra);
gout medication such as allopurinol (Zyloprim), colchicine (Colcrys), or probenecid (Benemid);
heart rhythm medication such as procainamide (Procan, Pronestyl), quinidine (Quinaglute, Quinidex, Quin-Release), or propranolol (Inderal);
other blood pressure medications, including diuretics (water pills);
pain, fever, or arthritis medication such as aspirin, indomethacin (Indocin), or propoxyphene (Darvon, Darvocet);
insulin or diabetes medication you take by mouth, such as chlorpropamide (Diabinese), tolazamide (Tolinase), or tolbutamide (Orinase); or
a sedative such as diazepam (Valium), chlordiazepoxide (Librax, Librium), or phenobarbital (Luminal, Solfoton).

This list is not complete and there may be other drugs that can interact with prazosin. Tell your doctor about all your prescription and over-the-counter medications, vitamins, minerals, herbal products, and drugs prescribed by other doctors. Do not start a new medication without telling your doctor.

Where can I get more information?

Your pharmacist can provide more information about prazosin.

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.
Every effort has been made to ensure that the information provided by Cerner Multum, Inc. ('Multum') is accurate, up-to-date, and complete, but no guarantee is made to that effect. Drug information contained herein may be time sensitive. Multum information has been compiled for use by healthcare practitioners and consumers in the United States and therefore Multum does not warrant that uses outside of the United States are appropriate, unless specifically indicated otherwise. Multum's drug information does not endorse drugs, diagnose patients or recommend therapy. Multum's drug information is an informational resource designed to assist licensed healthcare practitioners in caring for their patients and/or to serve consumers viewing this service as a supplement to, and not a substitute for, the expertise, skill, knowledge and judgment of healthcare practitioners. The absence of a warning for a given drug or drug combination in no way should be construed to indicate that the drug or drug combination is safe, effective or appropriate for any given patient. Multum does not assume any responsibility for any aspect of healthcare administered with the aid of information Multum provides. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the drugs you are taking, check with your doctor, nurse or pharmacist.