What Is Prazosin? Uses, Dosage, and What You Need to Know in 2026

Prazosin is a versatile medication with a long history of clinical use. Whether you've just been prescribed it or are trying to understand a current prescription, this guide covers everything you need to know about Prazosin: what it is, what it treats, how to take it, and what to watch for.

What Is Prazosin?

Prazosin is a prescription medication classified as an alpha-1 adrenergic receptor antagonist (alpha blocker). It works by blocking alpha-1 receptors on smooth muscle cells, causing blood vessels and other smooth muscles to relax. Brand name: Minipress (largely discontinued; most patients use the generic).

Prazosin was patented in 1965, approved by the FDA in 1974, and has been in continuous clinical use ever since. It is available only by prescription, comes as oral capsules, and is not a controlled substance.

What Is Prazosin Used For?

Prazosin has one FDA-approved indication and several established off-label uses:

FDA-approved: Hypertension (high blood pressure). Prazosin lowers blood pressure by relaxing blood vessel walls, reducing the resistance your heart pumps against. It is considered a second-line agent for hypertension.

Off-label: PTSD-associated nightmares. This is Prazosin's most recognized off-label use, supported by clinical trials in veterans. Studies show 50-70% reductions in nightmare frequency in responding patients. The 2023 VA/DoD PTSD guidelines conditionally recommend it.

Off-label: Benign prostatic hyperplasia (BPH). Prazosin was actually the first alpha blocker used for BPH, relaxing the smooth muscle of the prostate and urethra to improve urine flow.

Off-label: Raynaud's phenomenon. Used to reduce vasospasm in fingers and toes. Typical dose: 1 mg three times daily.

Off-label: Pheochromocytoma. Used preoperatively to control hypertensive episodes from this adrenal gland tumor.

What Dosage Forms Does Prazosin Come In?

Prazosin is available as oral capsules in three strengths:

1 mg capsules

2 mg capsules

5 mg capsules

How Is Prazosin Dosed?

Dosing depends on what condition is being treated:

Hypertension: Start 1 mg two to three times daily; increase gradually to 6–15 mg/day in divided doses. Maximum 20–40 mg/day for most patients.

PTSD nightmares: Start 1 mg at bedtime; titrate by 1–2 mg every 3–7 days. Maintenance commonly 3–15 mg nightly. Clinical trials have used up to 16 mg nightly in men and 7 mg in women.

BPH: 0.5–1 mg twice daily, maximum 4 mg/day.

How Should I Take Prazosin?

Take your first dose at bedtime to minimize dizziness and the first-dose blood pressure drop.

Take at evenly spaced intervals throughout the day if on multiple daily doses.

Do not drive or operate machinery for 24 hours after your first dose or after a dose increase.

Rise slowly from lying or sitting positions to reduce orthostatic dizziness.

Do not stop Prazosin abruptly without talking to your doctor—particularly if you take it for blood pressure.

Store at room temperature (68–77°F) away from moisture and heat.

Who Should Not Take Prazosin?

Anyone with a prior anaphylactic reaction to Prazosin or other quinazoline alpha-blockers (terazosin, doxazosin)

Patients with very low blood pressure (use with caution)

Pregnant women (Category C—use only if benefit clearly outweighs risk)

Patients with upcoming eye surgery should inform their surgeon (IFIS risk)

To understand how Prazosin works at the molecular level, see: How Does Prazosin Work? Mechanism of Action Explained in Plain English. If you're having trouble finding Prazosin at your pharmacy, medfinder can help locate it near you.