Prazosin — what it does and how to use it safely
Prazosin is a prescription medicine most often used to lower blood pressure and, off-label, to reduce nightmares from PTSD. It works by blocking alpha-1 receptors, which relaxes blood vessels and can also affect how the nervous system responds to stress. If you were prescribed prazosin, here’s what you need to know to use it safely and get the most benefit.
Who takes prazosin and why
Doctors commonly prescribe prazosin for high blood pressure when other meds aren’t right or as an add-on. Mental health clinicians may prescribe it at low doses to reduce nighttime nightmares and improve sleep in people with PTSD. Some people with urinary symptoms from an enlarged prostate notice relief because prazosin can relax smooth muscle in the urinary tract, but it’s not the first choice for every case.
Practical dosing and what to watch for
Start low and go slow. Typical starting doses are 1 mg at bedtime, then slowly increase over days based on response and side effects. For blood pressure, doctors often split the total daily dose into two or three doses. For PTSD-related nightmares, clinicians usually increase the nighttime dose gradually—common ranges for adults are 1–5 mg at night, sometimes higher under supervision. Never double doses on your own.
First-dose dizziness is common. Take the first dose at bedtime to reduce the chance of fainting or feeling lightheaded. Rise slowly from sitting or lying down for the first week or two. Check your blood pressure at home if you can, and call your provider if you get repeated dizziness, fainting, or very low readings.
Watch for these side effects: dizziness, lightheadedness, headache, nasal congestion, nausea, and fast heartbeat. Rare but serious problems include severe low blood pressure or priapism (long, painful erection). Seek urgent care for either.
Drug interactions matter. Combining prazosin with other blood pressure drugs, nitrates, or PDE5 inhibitors (like sildenafil) can cause a big drop in blood pressure. Tell every provider and your pharmacist about prazosin so they can spot risky combinations.
Special groups: older adults are more sensitive to the blood pressure effects and fall risk goes up. If you’re pregnant, breastfeeding, or have liver or kidney problems, talk with your doctor—dosing and risks may change. Don’t drink alcohol heavily while starting prazosin; it makes dizziness worse.
Practical tips: take the first dose at night, get up slowly, avoid sudden standing after sitting, keep a blood pressure log, and carry ID that lists your meds if you faint. If you plan to stop prazosin, ask your provider how to taper safely rather than stopping abruptly.
Questions for your doctor: Why did you choose prazosin for me? What dose should I start with and when will we adjust? What signs mean I should call you or go to ER? Clear answers will make using prazosin safer and easier.
