Generic Name: Prazosin Brand Name(s): Generics only. No brands available.

Know the basics

What is prazosin used for?

Prazosin is used with or without other medications to treat high blood pressure. Lowering high blood pressure helps prevent strokes, heart attacks, and kidney problems.

Prazosin belongs to a class of medications called alpha blockers. It works by relaxing and widening blood vessels so blood can flow more easily.

OTHER USES: This section contains uses of this drug that are not listed in the approved professional labeling for the drug but that may be prescribed by your health care professional. Use this drug for a condition that is listed in this section only if it has been so prescribed by your health care professional.

This drug may also be used to treat certain blood circulation disorders (Raynaud’s phenomenon). Prazosin may also be used to treat problems urinating due to an enlarged prostate (benign prostatic hyperplasia) or to help your body “pass,” or get rid of, kidney stones through urination.

How should I take prazosin?

Take this medication by mouth with or without food, usually two or three times daily or as directed by your doctor. If stomach upset occurs, take with food or milk. The dosage is based on your age, medical condition and response to therapy.

Prazosin can occasionally cause sudden fainting after the first dose and anytime that your dose is increased. To reduce your risk of fainting, the first dose prescribed by your doctor will be the smallest dose available. You should take this first dose as you are going to bed. This will decrease the possibility of fainting. Your dose may be gradually increased. Take your first new dose at bedtime when your dose is increased unless directed otherwise by your doctor.

Use this medication regularly in order to get the most benefit from it. To help you remember, take it at the same time(s) each day. If you are taking this medication for high blood pressure, it is important to continue taking it even if you feel well. Most people with high blood pressure do not feel sick. It may take up to several weeks before the full benefit of this drug takes effect.

Do not stop taking this medication without first consulting your doctor. Some conditions may become worse when the drug is abruptly stopped. Your dose may need to be gradually decreased.

Tell your doctor if your condition worsens (such as your routine blood pressure readings increase).

How do I store prazosin?

Prazosin is best stored at room temperature away from direct light and moisture. To prevent drug damage, you should not store prazosin in the bathroom or the freezer. There may be different brands of prazosin that may have different storage needs. It is important to always check the product package for instructions on storage, or ask your pharmacist. For safety, you should keep all medicines away from children and pets.

You should not flush prazosin down the toilet or pour them into a drain unless instructed to do so. It is important to properly discard this product when it is expired or no longer needed. Consult your pharmacist for more details about how to safely discard your product.

Know the precautions & warnings

What should I know before using prazosin?

When deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For this medicine, the following should be considered:

Allergies

Tell your doctor if you have ever had any unusual or allergic reaction to this medicine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.

Pediatric

Appropriate studies have not been performed on the relationship of age to the effects of prazosin in the pediatric population. Safety and efficacy have not been established.

Geriatric

No information is available on the relationship of age to the effects of prazosin in geriatric patients

Is it safe to take prazosin during pregnancy or breast-feeding?

There isn’t enough information about the safety of using this medication during pregnancy and breast-feeding. Please always consult with your doctor to weigh the potential benefits and risks before taking this medication.

Know the side effects

What are the side effects of prazosin?

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.

Not everyone experiences these side effects. There may be some side effects not listed above. If you have any concerns about a side-effect, please consult your doctor or pharmacist.

Know the interactions

What drugs may interact with prazosin?

Using this medicine with any of the following medicines is not recommended. Your doctor may decide not to treat you with this medication or change some of the other medicines you take.

  • Amifampridine

Using this medicine with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

  • Cobicistat
  • Tadalafil
  • Topotecan

Using this medicine with any of the following medicines may cause an increased risk of certain side effects, but using both drugs may be the best treatment for you. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

  • Acebutolol
  • Alprenolol
  • Atenolol
  • Betaxolol
  • Bevantolol
  • Bisoprolol
  • Bucindolol
  • Carteolol
  • Carvedilol
  • Celiprolol
  • Dilevalol
  • Esmolol
  • Labetalol
  • Levobunolol
  • Mepindolol
  • Metipranolol
  • Metoprolol
  • Nadolol
  • Nebivolol
  • Oxprenolol
  • Penbutolol
  • Pindolol
  • Propranolol
  • Sildenafil
  • Sotalol
  • Talinolol
  • Tertatolol
  • Timolol
  • Vardenafil

Does food or alcohol interact with prazosin?

Prazosin may interact with food or alcohol by altering the way the drug works or increase the risk for serious side effects. Please discuss with your doctor or pharmacist any potential food or alcohol interactions before using this drug.

What health conditions may interact with prazosin?

Prazosin may interact with your health condition. This interaction may worsen your health condition or alter the way the drug works. It is important to always let your doctor and pharmacist know all the health conditions you currently have, especially:

  • Angina (chest pain) or
  • Heart disease, severe or
  • Postural hypotension (low blood pressure)—Prazosin may make these conditions worse.
  • Cataract surgery—An eye problem called Intraoperative Floppy Iris Syndrome (IFIS) has occurred in patients who are taking or who have recently taken this medicine when they are having cataract surgery. You should tell your ophthalmologist (eye doctor) before your surgery if you are taking prazosin.
  • Kidney disease—Effects may be increased because of slower removal of the medicine from the body.

Understand the dosage

The information provided is not a substitute for any medical advice. You should ALWAYS consult with your doctor or pharmacist before using this medication.

What is the dose of prazosin for an adult?

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 is the dose of prazosin for a child?

The dosage has not been established in pediatric patients. It may be unsafe for your child. It is always important to fully understand the safety of the drug before using. Please consult with your doctor or pharmacist for more information.

How is prazosin available?

Prazosin is available in the following dosage forms and strengths:

Capsule: 1 mg; 2 mg; 5 mg

What should I do in case of an emergency or overdose?

In case of an emergency or an overdose, call your local emergency services (115) or go to your nearest emergency room.

Symptoms of overdose may include:

  • drowsiness
  • decreased reflexes
  • dizziness
  • lightheadedness
  • fainting

What should I do if I miss a dose?

If you miss a dose of prazosin, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and take your regular dose as scheduled. Do not take a double dose.

Hello Health Group does not provide medical advice, diagnosis or treatment.

Sources

Review Date: January 4, 2017 | Last Modified: January 4, 2017