Alpha blockerPrescription only
Prazosin
Tablet
Quick Summary
Prazosin relaxes blood vessels.
High blood pressure
Scorpion sting
Urinary symptoms
Medical Uses
High blood pressure: Add-on.
Scorpion sting: Under medical care.
Urinary symptoms: Sometimes.
How it's taken
The first dose is usually taken at bedtime because it can cause dizziness.
Your doctor decides the right dose for you. Follow their instructions and the label.
Common Side Effects
Dizziness
Especially after the first dose.
Fainting
Rarely.
Drowsiness
Sometimes.
Interactions
Other blood pressure medicines
Together they can lower blood pressure too much.
Sildenafil
Low blood pressure.
Critical Warnings
First-dose fainting
Lie down if dizzy.
Stand up slowly
To avoid falls.
Sources and further reading
Last updated 21 October 2026. For more detail, see these trusted health organisations.
- Prazosin: drug information(opens in a new tab) · MedlinePlus, US National Library of Medicine