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# Prazosin
## Overview
Prazosin is an alpha-1 adrenergic blocker that causes vasodilation.
## Primary Indications
* Hypertension
* Symptomatic benign prostatic hyperplasia (BPH)
* Off-label: PTSD-related nightmares
## Adult Dosing
* **Hypertension:** Initiate at 1 mg orally once or twice daily. Titrate slowly based on response, typically every 4-6 weeks. Usual maintenance dose: 3-15 mg/day divided into two doses. Maximum: 20 mg/day.
* **BPH:** Initiate at 1 mg orally once or twice daily. Titrate slowly based on response. Usual maintenance dose: 1-5 mg orally once or twice daily. Maximum: 10 mg/day.
* **PTSD Nightmares:** Initiate at 1 mg orally at bedtime. May increase by 1-2 mg every 1-2 weeks. Usual effective dose: 2-10 mg at bedtime. Maximum: 10 mg/day (though higher doses may be used under specialist supervision).
## Pediatric Dosing
Prazosin is generally not recommended for pediatric patients due to limited data and potential for adverse effects.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Consider a lower starting dose and slower titration. No specific dose reduction guidelines are universally established.
* **Hepatic Impairment:** Use with caution.
## Contraindications
* Hypersensitivity to prazosin or other quinazolines.
## Adverse Effects
* **Common:** Dizziness, headache, drowsiness, orthostatic hypotension (especially with the first dose), nausea, palpitations.
* **Serious:** Syncope (particularly with first dose), priapism.
## Key Drug Interactions
* **Other antihypertensives:** Additive hypotensive effect.
* **Diuretics:** Increased risk of hypotension.
* **Beta-blockers:** May increase the risk of orthostatic hypotension.
* **Phosphodiesterase-5 (PDE5) inhibitors:** Increased risk of symptomatic hypotension. Avoid concurrent use if possible, or use with extreme caution and monitor blood pressure closely.
## Monitoring
* Blood pressure (lying and standing) before and shortly after initiation or dose increase, and regularly thereafter.
* Monitor for signs of syncope or excessive dizziness.
* For PTSD nightmares, monitor for reduction in nightmare frequency and severity, and for any new adverse effects.
## Clinical Pearls
* **First-dose phenomenon:** Significant orthostatic hypotension and syncope can occur within 1-3 hours of the first dose or after a dose increase. Advise patients to take the first dose at bedtime and avoid driving or operating heavy machinery until they know how the drug affects them.
* Titrate slowly to minimize orthostatic side effects.
* For BPH, prazosin may be more effective in patients with moderate rather than severe symptoms.
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*Please verify current prescribing information for the most up-to-date recommendations. This information is intended for healthcare professionals and does not substitute for professional medical advice.*
