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# Prazosin
## Overview
Prazosin is a selective alpha-1 adrenergic blocker.
## Primary Indications
* Hypertension
* Symptomatic benign prostatic hyperplasia (BPH)
* Off-label: PTSD-related nightmares (though evidence is mixed and other agents may be preferred)
## Adult Dosing
* **Hypertension:** Start with 1 mg at bedtime. Titrate slowly, typically every 4-7 days, based on blood pressure response. Usual maintenance dose: 1 mg to 5 mg two to three times daily. Maximum dose: 20 mg daily (divided doses).
* **BPH:** Start with 1 mg at bedtime. Titrate slowly. Usual maintenance dose: 1 mg to 5 mg two to three times daily. Maximum dose: 20 mg daily (divided doses).
* **PTSD Nightmares (Off-label):** Doses can vary significantly. Common starting doses are 1 mg at bedtime, titrated up to 4-10 mg at bedtime. Higher doses are sometimes used but require careful monitoring.
## Pediatric Dosing
Dosing in children is not well-established and requires expert consultation. Limited data suggests starting doses of 5-10 mcg/kg/day in divided doses for hypertension, titrated up to a maximum of 25-50 mcg/kg/day or 10 mg daily, whichever is less.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustment is typically recommended, but caution and slower titration may be warranted in severe renal impairment.
## Contraindications
* Hypersensitivity to prazosin or other quinazolines.
## Adverse Effects
* **Common:** Dizziness, lightheadedness, headache, drowsiness, weakness, nausea, palpitations.
* **Serious:** Orthostatic hypotension (especially with the first dose or dose increases), syncope (fainting), priapism (rare but requires immediate medical attention), blurred vision, shortness of breath.
## Key Drug Interactions
* **Other Antihypertensives:** Additive hypotensive effect.
* **Diuretics:** Increased risk of severe hypotension.
* **Beta-blockers:** Can potentiate the first-dose hypotensive effect.
## Monitoring
* Blood pressure (supine and standing) before and after dose titration, especially with the first dose and with dose increases.
* Signs and symptoms of orthostatic hypotension (dizziness, lightheadedness, fainting).
* Efficacy for the intended indication.
## Clinical Pearls
* Administer the first dose at bedtime to minimize the risk of severe orthostatic hypotension and syncope.
* Advise patients to avoid driving or operating heavy machinery until they know how prazosin affects them.
* Instruct patients to rise slowly from a sitting or lying position.
* Avoid rapid dose increases.
* For BPH, therapeutic effects may take several weeks to become apparent.
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**Disclaimer:** This information is intended for healthcare professionals. It is essential to consult the most current prescribing information and clinical guidelines for complete and accurate details before making any treatment decisions.
