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Prazosin Dosage

Medically reviewed by Last updated on Nov 16, 2022.

Applies to the following strengths: 1 mg; 2 mg; 5 mg

Usual Adult Dose for Hypertension

Initial dose: 1 mg orally 2 or 3 times a day
Maintenance dose: 1 to 20 mg orally per day in divided doses


  • Titrate slowly as determined by blood pressure response.
  • Therapeutic dosages usually range from 6 to 15 mg per day in divided doses.
  • Total daily doses greater than 20 mg usually do not increase efficacy, but some patients may benefit from daily doses up to 40 mg per day in divided doses.

Renal Dose Adjustments

Data not available

Liver Dose Adjustments

Data not available

Dose Adjustments

Adding a diuretic or another antihypertensive agent:

  • Reduce the dose of this drug to 1 or 2 mg three times a day and then retitrate.

Coadministration with phosphodiesterase-5 (PDE-5) inhibitors:
  • Initiate the PDE-5 inhibitor at the lowest dose.


Safety and efficacy have not been established in children.

Consult WARNINGS section for additional precautions.


Data not available

Other Comments

Storage requirements: Protect from light.


  • Cardiovascular: Blood pressure (following the initial dose and dose adjustments)

Patient advice:
  • Advise patients how to avoid symptoms associated with lowering of blood pressure (e.g., dizziness, lightheadedness) and what to do if they occur. Also, encourage patients to avoid situations where injury could result if these symptoms occur.
  • Inform male patients about the seriousness of priapism and instruct them to seek immediate medical attention if it occurs.
  • Advise patients to report current or previous use of this drug to their ophthalmologist.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.