Prazosin

Prazosin capsules treat hypertension and may be used alone or with other antihypertensives. Blood-pressure lowering is part of broader cardiovascular risk management. The selected labels do not approve PTSD, nightmares or benign prostatic hyperplasia.

The 2023 VA/DoD guideline weakly suggests prazosin for PTSD-associated nightmares, with low confidence in the evidence; benefits and orthostatic risks require shared assessment. It suggests against prazosin monotherapy for overall PTSD treatment. Nightmare-specific use does not replace comprehensive PTSD care.

Start 1 mg orally two or three times daily. Increase slowly according to blood pressure; usual effective total 6–15 mg/day in divided doses. The label permits titration to 20 mg/day; higher totals usually add no efficacy, although selected patients may benefit up to 40 mg/day. Some can use twice-daily maintenance after titration. The 2 mg and 5 mg capsules are not starting doses.

VA/DoD Appendix B starts 1 mg at bedtime and titrates to clinical response; its listed range is 3–20 mg at bedtime. This is a supervised off-label range, not an automatic escalation or universal target. Slow titration and orthostatic assessment are essential.

When adding a diuretic or another antihypertensive, selected labels reduce prazosin to 1–2 mg three times daily and then retitrate to blood-pressure response. A PDE-5 inhibitor such as sildenafil or tadalafil adds hypotension risk; initiate the PDE-5 inhibitor at its lowest appropriate dose and review the complete regimen.

No fixed renal or hepatic adjustment algorithm is supplied in the selected labels. Individualize to blood-pressure response and tolerability; do not infer safety in organ dysfunction from the absence of a formula. Confirm the prescribed indication, strength and schedule before changing doses.

Known sensitivity to quinazolines, prazosin or any selected product’s ingredients.

The selected current U.S. labels have no boxed warning. Their first-dose syncope and priapism warnings remain clinically important.

Dizziness, headache, drowsiness, low energy, weakness, palpitations and nausea are frequent reported reactions. Edema, orthostatic hypotension, syncope, gastrointestinal symptoms and other reactions occur. Overdose may cause severe drowsiness or hypotension; seek urgent medical or Poison Help advice. Medical management supports circulation and renal function; prazosin is not dialyzable because of protein binding.

No adequate controlled pregnancy studies establish safety; use only when potential benefit justifies maternal/fetal risk. Small amounts appear in human milk and the labels advise caution during breastfeeding. Review indication and alternatives with the treating clinician.

Safety and effectiveness in children are unestablished. The selected labels provide no separate geriatric dosing schedule; response-based titration and protection against hypotension, sedation and falls are necessary.

A quantitative organ-impairment regimen is not established in these labels. Monitor clinical response and co-treatment risks. Animal and limited human pharmacology describe extensive metabolism and mainly biliary/fecal elimination, but this does not establish a dosing rule for liver disease.

Prazosin reduces peripheral resistance, with effects attributed in part to postsynaptic alpha-adrenoceptor blockade. Blood pressure falls while supine and standing; ordinary antihypertensive effects are usually not accompanied by reflex tachycardia, although tachycardia can occur around syncope.

Peak and half-life

Plasma peak about 3 hours; half-life about 2–3 hours.

Binding

Highly protein bound; no percentage is specified in the selected labels.

Metabolism

Extensive demethylation and conjugation described principally in animals, with limited human data suggesting similar handling.

Excretion

Mainly bile and feces; high binding limits dialysis removal.

• Follow blood pressure and orthostatic symptoms after initiation, dose changes and new antihypertensives.
• Assess dizziness, drowsiness, fainting and falls; review alcohol, heat exposure and co-medication.
• For off-label nightmare treatment, document nightmare response, sleep burden and tolerability without assuming overall PTSD benefit.
• Review cataract surgery plans, pregnancy/breastfeeding and relevant laboratory testing.

• Confirm whether the prescription is for hypertension or nightmares; follow that schedule and contact the clinician before changing it.
• Rise slowly. Avoid hazardous tasks for 24 hours after the first dose or a dose increase.
• Report fainting or troublesome dizziness; seek immediate care for an erection lasting over 4 hours.
• Tell the eye surgeon about alpha-blocker use and tell all prescribers about sildenafil, tadalafil and blood-pressure medicines.

Dosage form

Hard gelatin capsule · 1 mg

Appearance

Dark green cap and light brown body

Imprint

019 on cap; novitium on body

Example NDC

70954-019-50 · 90 capsules

Selected oral prazosin hydrochloride capsules contain 1, 2 or 5 mg prazosin equivalent. Prasco authorized-generic and Novitium packages have different colors and imprints; verify the dispensed manufacturer rather than identifying strength by color alone.

Selected Novitium capsules: store at 20–25°C, protect from moisture and light, and dispense in a tight, light-resistant container. Follow the specific dispensed label and keep out of children’s reach.