Prazosin

Generic name: prazosin
Brand name: Minipress
Dosage form: oral capsule (1 mg; 2 mg; 5 mg)
Drug class: Antiadrenergic agents, peripherally acting

Medically reviewed by A Ras MD.

What is prazosin?

Prazosin is a prescription medicine that is used to treat high blood pressure. Prazosin may be given to you for other reasons.

Description

Prazosin Hydrochloride Capsules USP, a quinazoline derivative, is the first of a new chemical class of antihypertensives. It is the hydrochloride salt of 1-(4-amino-6,7-dimethoxy2-quinazolinyl)-4-(2-furoyl) piperazine and its structural formula is:

Molecular formula C19H21N5O4·HCl

It is a white, crystalline substance, slightly soluble in water and isotonic saline, and has a molecular weight of 419.87. Each capsule for oral use contains prazosin hydrochloride equivalent to 1 mg, 2 mg or 5 mg of prazosin.

Inert ingredients in the formulations are: lactose monohydrate, polysorbate 80, hypromellose, corn starch, magnesium stearate, titanium dioxide, sodium laurel sulfate, gelatin, shellac, propylene glycol, ammonia, potassium hydroxide, and black iron oxide. In addition, the 2 mg capsules contain FD&C Blue 1 and FD&C Red 3; and the 5 mg capsules contain FD&C Blue 1.

Before taking prazosin, tell your doctor:

If you are allergic to prazosin; any part of this medicine; or any other drugs, foods, or substances. Tell your doctor about the allergy and what signs you had.

This medicine may interact with other drugs or health problems.

Tell your doctor and pharmacist about all of your drugs (prescription or OTC, natural products, vitamins) and health problems. You must check to make sure that it is safe for you to take prazosin with all of your drugs and health problems. Do not start, stop, or change the dose of any drug without checking with your doctor.

What are some things I need to know or do while I take prazosin?

Tell all of your health care providers that you take prazosin. This includes your doctors, nurses, pharmacists, and dentists.
Avoid driving and doing other tasks or actions that call for you to be alert until you see how prazosin affects you.
To lower the chance of feeling dizzy or passing out, rise slowly if you have been sitting or lying down. Be careful going up and down stairs.
Check your blood pressure as you have been told.
This medicine may affect certain lab tests. Tell all of your health care providers and lab workers that you take prazosin.
If you are having cataract surgery or other eye procedure, talk with your doctor.
If you are taking prazosin and have high blood pressure, talk with your doctor before using OTC products that may raise blood pressure. These include cough or cold drugs, diet pills, stimulants, ibuprofen or like products, and some natural products or aids.
Talk with your doctor before you drink alcohol.
Be careful in hot weather or while being active. Drink lots of fluids to stop fluid loss.
Tell your doctor if you are pregnant or plan on getting pregnant. You will need to talk about the benefits and risks of using prazosin while you are pregnant.
Tell your doctor if you are breast-feeding. You will need to talk about any risks to your baby.

How is prazosin best taken?

Use prazosin as ordered by your doctor. Read all information given to you. Follow all instructions closely.

Take with or without food.
Keep taking prazosin as you have been told by your doctor or other health care provider, even if you feel well.

What do I do if I miss a dose?

Take a missed dose as soon as you think about it.
If it is close to the time for your next dose, skip the missed dose and go back to your normal time.
Do not take 2 doses at the same time or extra doses.

What are the side effects of prazosin that I need to call my doctor about immediately?

WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:

Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing, swallowing, or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.
Very bad dizziness or passing out.
Blurred eyesight.
A fast heartbeat.
A heartbeat that does not feel normal.
Low mood (depression).
Shortness of breath.
Swelling in the arms or legs.
Call your doctor right away if you have a painful erection (hard penis) or an erection that lasts for longer than 4 hours. This may happen even when you are not having sex. If this is not treated right away, it may lead to lasting sex problems and you may not be able to have sex.

What are some other side effects of prazosin?

All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your doctor or get medical help if any of these side effects or any other side effects bother you or do not go away:

Dizziness.
Feeling sleepy.
Feeling tired or weak.
Headache.
Upset stomach.

These are not all of the side effects that may occur. If you have questions about side effects, call your doctor. Call your doctor for medical advice about side effects.

You may report side effects to the FDA at 1-800-332-1088. You may also report side effects at https://www.fda.gov/medwatch.

If overdose is suspected:

If you think there has been an overdose, call your poison control center or get medical care right away. Be ready to tell or show what was taken, how much, and when it happened.

How do I store and/or throw out prazosin?

Store at room temperature.
Protect from light.
Store in a dry place. Do not store in a bathroom.
Keep all drugs in a safe place. Keep all drugs out of the reach of children and pets.
Throw away unused or expired drugs. Do not flush down a toilet or pour down a drain unless you are told to do so. Check with your pharmacist if you have questions about the best way to throw out drugs. There may be drug take-back programs in your area.