Uses
What is prazosin used for?
Prazosin is commonly used to treat high blood pressure (hypertension).
Prazosin may also be used for other conditions as determined by your healthcare provider.
How does prazosin work (mechanism of action)?
Prazosin is an alpha blocker. It works to relax your blood vessels and make them more open. As a result, your blood can move through them more easily. This lowers blood pressure.
How is prazosin supplied (dosage forms)?
Prazosin is available as Minipress and generic prazosin in the following dosage forms that are taken by mouth.
- 1 mg oral capsules
- 2 mg oral capsules
- 5 mg oral capsules
How should I store prazosin?
Prazosin should be stored at room temperature, between 68 F to 77 F (20 C to 25 C). It can be exposed to temperatures between 59 F to 86 F (15 C to 30 C) for shorter periods of time, such as when transporting it. Store in a cool, dry place.
Side Effects
What are the most common side effects of prazosin?
The most common side effects of prazosin are listed below. Tell your healthcare provider if you have any of these side effects that bother you.
- Dizziness
- Drowsiness and tiredness
- Headache
- Feeling weak
- Feeling like your heart is pounding or skipping (palpitations)
- Nausea
There may be other side effects of prazosin that are not listed here. Contact your healthcare provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088. In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.
What are the serious side effects of prazosin?
While less common, the most serious side effects of prazosin are described below, along with what to do if they happen.
Severe Allergic Reactions. Prazosin may cause allergic reactions, which can be serious. Stop using prazosin and get help right away if you have any of the following symptoms of a serious allergic reaction.
- Breathing problems or wheezing
- Racing heart
- Fever or general ill feeling
- Swollen lymph nodes
- Swelling of the face, lips, mouth, tongue, or throat
- Trouble swallowing or throat tightness
- Itching, skin rash, or pale red bumps on the skin called hives
- Nausea or vomiting
- Dizziness, feeling lightheaded, or fainting
- Stomach cramps
- Joint pain
Low Blood Pressure Upon Standing (Orthostatic Hypotension). Prazosin may cause a sudden drop in blood pressure when standing up from a seated or lying position. This may result in fainting, especially when you first start prazosin. To help prevent this side effect, your healthcare provider may tell you to take your first dose of prazosin at bedtime. Tell your healthcare provider right away if you have any of the following symptoms of orthostatic hypotension.
- Dizziness, feeling lightheaded, or fainting upon standing
- Blurred vision
- Confusion
- Feeling weak
- Feeling like your heart is racing or skipping (palpitations)
Painful, Prolonged Erection (Priapism). Prazosin may cause an unwanted erection that is persistent, painful, and that may occur without sexual arousal. Priapism may cause permanent damage to the penis. Stop taking prazosin and get emergency help right away if you have any of the following symptoms of priapism.
- Erection lasting for more than 4 hours
- Erection that is unrelated to sexual stimulation
- Painful or tender penis
Warnings & Precautions
Who should not use prazosin?
Allergies to Ingredients. People who are allergic to any of the following should not use prazosin.
- Prazosin
- Prazosin HCl
- Prazosin hydrochloride
- Minipress
- A medicine known as a quinazoline, such as doxazosin or terazosin
- Any of the ingredients in the specific product dispensed
Your pharmacist can tell you all of the ingredients in the specific prazosin products they stock.
What should I know about prazosin before taking it?
Do not take prazosin unless it has been prescribed to you by a healthcare provider. Take it as prescribed.
Do not share prazosin with other people, even if they have the same condition as you. It may harm them.
Keep prazosin out of the reach of children.
Prazosin may cause dizziness and drowsiness. Do not drive or do activities that could be dangerous for 24 hours after your first dose of prazosin or after your dose is increased. Wait to drive or do other activities that require alertness or coordination until you know how prazosin affects you.
The following tips may help to lessen dizziness with prazosin.
- Get up slowly when you stand up
- Limit the amount of alcohol you drink
- Do not stand or exercise for long periods of time without taking breaks, especially in hot weather
What should I tell my healthcare provider before using prazosin?
Tell your healthcare provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them determine if prazosin is right for you.
In particular, make sure that you discuss any of the following.
Planned Eye Surgery. Prazosin may raise the risk of eye problems called intraoperative floppy iris syndrome during or after cataract or glaucoma surgery. Tell your healthcare provider if you are planning to have eye surgery. They may recommend that you wait until after the surgery is over to start prazosin.
Other Medicines and Supplements. Prazosin may interact with other medicines and supplements. Before using prazosin, tell your healthcare provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.
Pregnancy. It is not known if prazosin could affect pregnancy or if it could harm an unborn baby. Tell your healthcare provider if you are or plan to become pregnant. Your healthcare provider will advise you if you should take prazosin while you are pregnant or trying to get pregnant.
Breastfeeding. Prazosin passes into breast milk. Tell your healthcare provider if you are breastfeeding or plan to breastfeed. Your healthcare provider will advise you if you should take prazosin while breastfeeding.
Interactions
Does prazosin interact with foods or drinks?
There are no known interactions between prazosin and foods.
Drinking alcohol may increase the chance of side effects from prazosin, such as dizziness or fainting. It is best to limit the amount of alcohol you drink with prazosin.
Does prazosin interact with other medicines (drug interactions)?
Always tell your healthcare provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.
In particular, make sure that you discuss if you are using any of the following before taking prazosin.
- Other medicines for high blood pressure, such as propranolol (Inderal LA, Innopran XL)
- A diuretic, also called a water pill, which is a medicine used to reduce edema (fluid retention) and blood pressure
- A type of medicine called a phosphodiesterase-5 (PDE-5) inhibitor, such as sildenafil (Viagra, Revatio, and others), tadalafil (Cialis and others), or vardenafil (Levitra, Staxyn), which are used for erectile dysfunction or pulmonary arterial hypertension
This may not be a complete list of medicines that can interact with prazosin. Always check with your healthcare provider.
Overdose/Missed Dose
What should I do if I accidentally take too much prazosin?
If you or someone else has used too much prazosin, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.
What should I do if I miss a dose of prazosin?
If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and only take the next dose. Do not take double or extra doses.
Are you currently using Prazosin (Minipress)?
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