Prazosin

Medically reviewed by Melissa Badowski, PharmD, MPH, FCCP on May 28, 2023
Written by Alex Brewer, PharmD, MBA

This article describes prazosin’s uses, side effects, and more. Below you’ll also find some coupon options to help save on the cost of prazosin.

Prazosin may cause mild or serious side effects. More common mild side effects of prazosin and its serious side effects are listed below. This article doesn’t include all possible side effects of the drug. Side effects can vary based on your age, overall health, and any other medications you take.

To learn more about prazosin’s side effects, talk with your doctor or pharmacist. You can also read the prescribing information* for prazosin.

* To view prazosin’s prescribing information, see the “Article resources” section below.

Mild side effects

More common mild side effects reported with prazosin are listed below.

This article doesn’t include all possible mild side effects of the drug. To learn more about prazosin’s side effects, see the prescribing information* for prazosin.

With many drugs, mild side effects may go away within a few days or a couple of weeks. If the side effects are bothersome, tell your doctor or pharmacist. They may be able to suggest ways to manage them.

Prazosin oral capsule’s mild side effects include:

• dizziness
• headache
• feeling sleepy or lacking energy
• weakness
• mild allergic reaction†

* To view prazosin’s prescribing information, see the “Article resources” section below.
† For details about this side effect, see the “Interactions and warnings for prazosin” section below.

Serious side effects

Serious side effects of prazosin are listed below.

This article doesn’t include all possible serious side effects of the drug. To learn more about prazosin’s side effects, see the prescribing information* for prazosin.

With many drugs, serious side effects are possible but not common. If you have serious side effects from this drug, call your doctor right away. If you’re having severe symptoms or a medical emergency, call 911 or a local emergency number.

In general, prazosin’s serious side effects include:

• depression
• erectile dysfunction
• fainting, especially after your first prazosin dose
• hallucinations (seeing or hearing things that aren’t really there)
• low blood pressure when standing or sitting up, which can lead to fainting
• priapism (long lasting erection that needs to be treated immediately)
• severe allergic reaction†

* To view prazosin’s prescribing information, see the “Article resources” section below.
† For details about this side effect, see the “Interactions and warnings for prazosin” section below.

Below you’ll find answers to a few commonly asked questions about prazosin.

Can prazosin be used for nightmares, sleep, anxiety, PTSD, or BPH?

Possibly. That said, prazosin is not approved for the following uses:

• nightmares
• trouble sleeping
• anxiety
• post-traumatic stress disorder (PTSD)
• benign prostatic hyperplasia (BPH), which is also referred to as enlarged prostate

Still, doctors may prescribe the drug off-label for these and other uses. “Off-label” means a drug is prescribed for a condition other than its approved uses.

Talk with your doctor if you’d like to learn more about possible off-label uses for prazosin. Also, ask your doctor about treatment options that are approved for the conditions listed above.

Are brand-name versions of prazosin available?

Yes, a brand-name version is available for the generic medication prazosin. It’s called Minipress.

A generic medication is an identical copy of the active drug in a brand-name medication. (An active drug is the ingredient that makes a medication work.) Generics usually cost less than brand-name drugs. And they’re thought to be as safe and effective as the brand-name versions.

Minipress is available in the same form and strengths as generic prazosin. Talk with your doctor or pharmacist if you’d like to learn more about brand-name Minipress.

Does prazosin cause weight gain or weight loss?

No, it’s not thought to. Weight gain and weight loss weren’t reported in studies of prazosin.

Some other medications prescribed to treat high blood pressure may cause weight gain. Examples include beta-blockers such as metoprolol (Toprol XL, Lopressor) and carvedilol (Coreg). However, prazosin isn’t expected to cause this side effect.

Talk with your doctor if you have concerns about your weight. You could ask whether any medications you take could be affecting it.

Is prazosin a controlled substance?

No, prazosin is not a controlled substance.

Controlled substances have the potential to be misused or cause dependence. (With misuse, a drug is taken in a way other than how a doctor prescribes it. With dependence, your body needs the drug in order to function like usual.)

Healthcare professionals must follow strict rules from the government when prescribing controlled substances.

Examples of controlled substances include alprazolam (Xanax) and hydrocodone. However, prazosin isn’t a controlled substance.

If you’d like to know more about this, talk with your doctor or pharmacist.

How does prazosin work? And how long does it take to start working?

Prazosin is used to treat high blood pressure. It works by relaxing muscles in the walls of your blood vessels. This lowers the pressure on blood moving through the vessels, allowing it to flow more easily.

Prazosin has a half-life of about 2-3 hours. A drug’s half-life describes how long it takes your body to clear half a dose of the drug after you take it.

Prazosin begins working within a few hours after you take a dose. But it may take a few weeks for your blood pressure to show long-term changes.

Talk with your doctor if you have questions about how they’ll monitor whether prazosin is working to manage your condition.

The Food and Drug Administration (FDA) approves prescription drugs such as prazosin for certain conditions. The approved use of prazosin is described below.

Use for high blood pressure

Doctors may prescribe prazosin oral capsule to treat high blood pressure. It’s used for this purpose in adults. It’s usually prescribed as a long-term treatment.

With high blood pressure, the force of blood on the walls of your blood vessels is too high. High blood pressure usually doesn’t cause symptoms, unless it suddenly becomes extremely high. Even so, high blood pressure can cause damage to other body organs over time. This raises your risk for certain health problems, including heart attack, stroke, kidney disease, and others.

Prazosin is prescribed alone or together with other medications for treating high blood pressure.

The dosage of prazosin your doctor prescribes may vary based on your condition and certain other factors. Talk with your doctor about the dosage you should take.

Taking prazosin

Prazosin oral capsule is taken by mouth, with or without food.

Your doctor will talk with you about how to take prazosin. They’ll explain how much to take and how often. Always follow your doctor’s recommendation.

Overdose of prazosin

You should not take more prazosin than your doctor prescribes. For some drugs, doing so may lead to serious side effects or overdose.

If you think you’ve taken too much prazosin, call your doctor or pharmacist right away. Or you could call 800-222-1222 to speak with someone at America’s Poison Centers. You can also use its online resource. If you have concerning symptoms, call 911 or a local emergency number immediately. You can also go to the closest emergency room.

Below, you’ll find information about prazosin’s possible interactions and warnings.

Interactions of prazosin

For some medications, certain things may affect how the drug works. These include getting vaccines, consuming alcohol or certain foods, or taking the drug with other medications. This effect is called a drug interaction.

Before you take prazosin, ask your doctor to check for possible interactions. Be sure to tell them about any of the following you take or use:

• prescription medications
• over-the-counter medications
• vitamins, herbs, or supplements

To learn about drug-condition interactions, see the “Warnings for prazosin” section below.

Warnings for prazosin

Some people should not take prazosin, and others should use it cautiously.

Prazosin could cause harm to people with certain health conditions. This effect is called a drug-condition interaction. Other factors can also affect whether prazosin is a safe option for you.

Ask your doctor about specific warnings for prazosin, and be sure to tell your doctor about your:

• current health, including any allergies to medications
• past health conditions or surgeries

Allergic reaction

Prazosin can cause an allergic reaction in some people. Severe allergic reactions are rare but possible.

If you’ve had an allergic reaction to prazosin or any of its ingredients, your doctor will likely not prescribe prazosin. They can tell you about medications that are safer options for you.

A mild allergic reaction may cause the following symptoms:

• skin rash
• itchiness
• flushing (temporary warmth, redness, or deepening of skin color)

A severe allergic reaction may cause the following symptoms:

• swelling under your skin, usually in your hands, feet, eyelids, or lips
• swelling of your mouth, throat, or tongue, which can cause breathing problems

If you have an allergic reaction to prazosin, call your doctor right away. If you have severe symptoms, call 911 or a local emergency number.

Pregnancy or breastfeeding and prazosin

Information about prazosin and pregnancy and breastfeeding is described below.

Prazosin and pregnancy

It’s not known whether prazosin should be taken during pregnancy. But there are risks with having unmanaged high blood pressure while pregnant. (Keep in mind that prazosin is used for managing this condition.)

If you’re planning a pregnancy or can become pregnant, talk with your doctor about high blood pressure treatment options during pregnancy. Together, you can discuss the risks and benefits of your treatment options and decide whether you should take prazosin during pregnancy.

Prazosin and breastfeeding

It’s not known whether prazosin should be taken while breastfeeding. If you’re currently breastfeeding or planning to do so, talk with your doctor before taking this medication.

You may be able to save money on your prescription for prazosin by using our Perks discount coupons. They can be found at the end of this article.

If you have questions about how to pay for prazosin, talk with your doctor or pharmacist.

Note: Optum Perks coupons cannot be used with insurance copays or benefits.

This article describes prazosin’s uses and dosage, ways to save on cost, and more. Let your doctor know if you have questions about prazosin or would like more details about it.

Here’s a list of some possible questions you may want to ask your doctor:

• Does prazosin cause changes in urination?
• How does prazosin compare with other drugs used to manage blood pressure?
• If I have side effects from prazosin, can you prescribe a lower dose for me to try?
• Do any medications I take interact with prazosin?
• Can prazosin cause hair loss?

• Food and Drug Administration. (2023). Orange Book: Approved drug products with therapeutic equivalence evaluations. https://www.accessdata.fda.gov/scripts/cder/ob/index.cfm
• Prazosin hydrochloride- prazosin hydrochloride capsule. (2023). https://nctr-crs.fda.gov/fdalabel/services/spl/set-ids/fa43e7f9-cab1-99ad-e053-6394a90a732f/spl-doc

Disclaimer: Optum Perks has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.