Health Library

Prazosin (By mouth)

Prazosin (PRAZ-oh-sin)

Treats high blood pressure.

Brand Name(s):

Minipress

When This Medicine Should Not Be Used:

How to Use This Medicine:

Capsule

• Take your medicine as directed. Your dose may need to be changed several times to find what works best for you.
• Missed dose: Take a dose as soon as you remember. If it is almost time for your next dose, wait until then and take a regular dose. Do not take extra medicine to make up for a missed dose.
• Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light.

Drugs and Foods to Avoid:

Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.

• Some medicines can affect how prazosin works. Tell your doctor if you also use any of the following:
  • Allopurinol, aspirin, chlordiazepoxide, colchicine, diazepam, digoxin, indomethacin, phenobarbital, phenylbutazone, probenecid, propoxyphene, vardenafil
  • Blood pressure medicine (including propranolol)
  • Diuretic (water pill)
  • Insulin or diabetes medicine that you take by mouth (including chlorpropamide, tolazamide, tolbutamide)
  • Medicine to treat erectile dysfunction (including sildenafil, tadalafil)
  • Medicine to treat heart rhythm problems (including procainamide, quinidine)

Warnings While Using This Medicine:

• Tell your doctor if you are pregnant or breastfeeding, or if you have kidney disease or cataracts.
• This medicine may cause the following problems:
  • Prolonged erection of the penis
  • Serious eye problem called Intraoperative Floppy Iris Syndrome (IFIS) in patients having an eye procedure (including cataract surgery)
• This medicine could lower your blood pressure too much, especially when you first use it or if you are dehydrated. This can make you dizzy or lightheaded. Do not drive or do anything else that could be dangerous until you know how this medicine affects you. Stand or sit up slowly if you feel lightheaded or dizzy. These symptoms may be worse if you drink alcohol.
• Drink plenty of fluids if you exercise or sweat more than usual while you are using this medicine.
• Tell any doctor or dentist who treats you that you are using this medicine. This medicine may affect certain medical test results.
• Your doctor will do lab tests at regular visits to check on the effects of this medicine. Keep all appointments.
• Keep all medicine out of the reach of children. Never share your medicine with anyone.

Possible Side Effects While Using This Medicine:

Call your doctor right away if you notice any of these side effects:

• Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing
• Fast, pounding, or uneven heartbeat
• Lightheadedness, dizziness, fainting
• Painful erection of your penis for more than 4 hours

If you notice these less serious side effects, talk with your doctor:

• Headache, drowsiness
• Nausea
• Tiredness or weakness

If you notice other side effects that you think are caused by this medicine, tell your doctor

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088

Last Updated: 9/6/2024