MedeliX
Start asking

Prazosin

ATC code C02CA01

Key facts
Active substance
Prazosin
ATC code
C02CA01
Authorisation
authorised nationally; no central EU authorisation
Information as of
2026-10-29

Key facts

Prazosin is a quinazoline alpha-1 blocker. Per the US prescribing information, its capsules are used to treat hypertension.

What it is used for

  • Hypertension, to lower blood pressure and thereby the risk of fatal and nonfatal cardiovascular events

Dosing

  • Initial dose 1 mg two or three times a day
  • Slowly increase to a total daily dose of 20 mg in divided doses; commonly used dosages 6 mg to 15 mg daily
  • Doses above 20 mg usually do not increase efficacy; a few patients may benefit from up to 40 mg daily in divided doses
  • When adding a diuretic or other antihypertensive, reduce prazosin to 1 mg or 2 mg three times a day and retitrate
  • Start PDE-5 inhibitors at the lowest dose

Contraindications

  • Known sensitivity to quinazolines, prazosin or any of the inert ingredients

Important warnings

  • Syncope with sudden loss of consciousness, usually within 30 to 90 minutes of the initial dose; incidence about 1% with an initial dose of 2 mg or greater; limit the initial dose to 1 mg
  • Hypotension when combined with a beta-blocker such as propranolol
  • Intraoperative floppy iris syndrome during cataract surgery

Side effects

  • Most frequent: dizziness 10.3%, headache 7.8%, drowsiness 7.6%, lack of energy 6.9%, weakness 6.5%, palpitations 5.3%, nausea 4.9%
  • In 1–4%: vomiting, diarrhea, constipation, edema, orthostatic hypotension, dyspnea, syncope, depression, rash, urinary frequency, blurred vision
  • Rarely: priapism, impotence, incontinence

Interactions

  • Diuretics and other antihypertensives: reduce the prazosin dose
  • PDE-5 inhibitors: additive blood pressure lowering and symptomatic hypotension
  • Beta-blockers such as propranolol: hypotension

Pregnancy and breastfeeding

  • No adequate studies in pregnant women; see the full text
  • Excreted in small amounts in human milk; use caution when nursing

Summary of the official product information, written with AI on 2026-10-29. Every number was checked automatically against the original text. Not reviewed by a physician – the full official text is authoritative.

Full official text →

Common questions – ask Medelix

For patients

Patient information (US)

This product has no separate US patient information.

Authorisation and brand names by country

Medicines with exactly this active-substance composition, as listed in the national registers – alphabetical and without ranking. Whether a product is currently available is not shown here.

Brand names in 5 more European countries
Cyprus
Atodel
Finland
Pratsiol
France
Alpress L.P.
Ireland
Hypovase
Spain
Minipres

EMA – Article 57 product data (EU/EEA), 2026-10-29

Medelix receives no money from pharmaceutical companies. Brand names are listed alphabetically and without ranking.

Other substances in the same group

Another question about this substance?

Medelix answers clinical questions from guidelines, studies and product information – every claim with its source.

Sources

  1. U.S. Food and Drug Administration. Prazosin Hydrochloride (Prasco Laboratories) – Prescribing Information, 2026-03-06. DailyMed (NLM), 2026-10-29. https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=cbe89216-7dea-43d7-b12e-44ccfb69af3d

Editorial: Medelix editorial team · last updated 2026-10-29 · How these pages are made · Report an error

Source: U.S. Food and Drug Administration (FDA), prescribing information, via DailyMed (NLM); public domain. Not advertising, not a treatment recommendation. For questions about your own treatment, ask your doctor or pharmacist.