Skip to Content

Prazosin

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

Medically reviewed on December 15, 2017

What is prazosin?

Prazosin is in a group of drugs called alpha-adrenergic (AL-fa ad-ren-ER-jik) blockers. Prazosin relaxes your veins and arteries so that blood can more easily pass through them.

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

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

Important Information

You should not use this medication if you are allergic to prazosin or similar medicines such as alfuzosin (Uroxatral), doxazosin (Cardura), silodosin (Rapaflo), tamsulosin (Flomax), or terazosin (Hytrin).

Prazosin may cause dizziness or fainting, especially when you first start taking it or whenever your dose is changed. 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.

Prazosin can affect your pupils during cataract surgery. Tell your eye surgeon ahead of time that you are using this medication. Do not stop using prazosin before surgery unless your surgeon tells you to.

Tell your doctor about all other medications you use, especially other blood pressure medications including diuretics (water pills).

Before taking this medicine

You should not use this medication if you are allergic to prazosin or similar medicines such as alfuzosin (Uroxatral), doxazosin (Cardura), silodosin (Rapaflo), tamsulosin (Flomax), or terazosin (Hytrin).

Prazosin can affect your pupils during cataract surgery. Tell your eye surgeon ahead of time that you are using this medication. Do not stop using prazosin before surgery unless your surgeon tells you to.

FDA pregnancy category C. It is not known whether prazosin will harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant while using this medication.

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 exactly as prescribed by your doctor. Do not take in larger or smaller amounts or for longer than recommended. Follow the directions on your prescription label.

Your doctor may occasionally change your dose to make sure you get the best results.

Prazosin lowers blood pressure and may cause dizziness or fainting, especially when you first start taking it or whenever your dose is changed. Call your doctor if you have severe dizziness or feel like you might pass out.

You may feel very dizzy when you first wake up. Be careful when standing or sitting up from a lying position.

Your blood pressure will need to be checked often. Visit your doctor regularly.

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.

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 diuretics (water pills). Tell your doctor if you have a prolonged illness that causes diarrhea or vomiting.

Store at room temperature away from moisture and heat.

What happens if I miss a dose?

Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Overdose symptoms may include extreme drowsiness or fainting.

What should I avoid while taking prazosin?

Prazosin may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be 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.

Drinking alcohol can increase certain 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 a serious side effect such as:

  • fast or pounding heartbeats or fluttering in your chest;

  • feeling like you might pass out;

  • trouble breathing;

  • 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:

  • mild dizziness;

  • weakness, tired feeling, drowsiness;

  • headache; or

  • nausea.

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.

See also: Side effects (in more detail)

Prazosin dosing information

Usual Adult Dose for Hypertension:

Initial dose: 1 mg orally 2 or 3 times a day
Maintenance dose: 1 to 20 mg orally per day in divided doses

Comments:
-Titrate slowly as determined by blood pressure response.
-Therapeutic dosages usually range from 6 to 15 mg per day in divided doses.
-Total daily doses greater than 20 mg usually do not increase efficacy, but some patients may benefit from daily doses up to 40 mg per day in divided doses.

What other drugs will affect prazosin?

Tell your doctor about all other medications you use, especially:

  • propranolol (Inderal, Innopran); or

  • other blood pressure medications, including diuretics (water pills).

This list is not complete and other drugs may interact with prazosin. Tell your doctor about all medications you use. This includes prescription, over-the-counter, vitamin, and herbal products. Do not start a new medication without telling your doctor.

Further information

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.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Hide