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Prazosin

Brand names: Minipress

Prazosin lowers blood pressure. It's also widely used off-label for PTSD nightmares.

Brand namesMinipress
Type of medicineAlpha blocker
Prescription?Prescription
ImportantThis page is general information, not a prescription. Don't start, stop, or change a medicine without talking to your provider or pharmacist.

Overview

The first dose can cause dizziness or fainting, so it's started at bedtime at a low dose.

What it's used for

  • High blood pressure
  • Off-label: PTSD-related nightmares
  • Off-label: Raynaud's

How to take it

  • Take the first dose at bedtime.
  • Stand up slowly. If you miss several days, ask before restarting.

Your dose depends on your health and other medicines. Always follow your prescription label, and ask your pharmacist if anything is unclear.

Side effects

Common side effects

  • Dizziness
  • Headache
  • Drowsiness
  • Low energy
Call 911Fainting
Call 911An erection lasting more than 4 hours

Warnings

  • Tell your eye surgeon you take it before cataract surgery.

Other medicines, foods, and alcohol

  • Other blood pressure medicines and ED medicines add to dizziness.

Tell your provider and pharmacist about every medicine, vitamin, and supplement you take.

Pregnancy and breastfeeding

Talk with your provider.

Missed doses, overdose, and storage

If you miss a dose

Take it as soon as you remember, unless it's almost time for your next dose. Then skip the missed dose. Don't take two doses at once.

If someone takes too much

Call Poison Control at 1-800-222-1222 or get help online at poison.org. Call 911 if the person collapses, has a seizure, has trouble breathing, or can't be woken.

Storing it

Store at room temperature, away from heat and moisture (not in the bathroom), and out of reach of children and pets.

Conditions it's used for

Sources

Last updated 2026-11-13.