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# Prazosin
## Overview
Prazosin is an alpha-1 adrenergic blocker used primarily for hypertension and off-label for nightmares associated with PTSD.
## Primary Indications
* Hypertension
* Symptomatic nightmares in PTSD (off-label)
## Adult Dosing
* **Hypertension:** Start with 1 mg orally twice daily. Titrate slowly based on blood pressure response. Typical maintenance dose is 1-5 mg orally twice daily. Maximum dose is typically 20 mg orally daily (divided into two doses).
* **PTSD Nightmares:** Start with 1 mg orally at bedtime. May increase by 1-2 mg every 1-2 weeks. Typical effective dose is 3-10 mg orally at bedtime. Maximum dose not well established but generally kept below 10 mg nightly.
## Pediatric Dosing
* **Hypertension:** Limited data available. Pediatric hypertension guidelines suggest starting doses as low as 0.5 mg/m²/day or 0.025 mg/kg/day in divided doses, titrating up cautiously.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustment is usually recommended, but caution and slower titration may be warranted due to potential accumulation.
* **Hepatic Impairment:** Use with caution.
## Contraindications
* Known hypersensitivity to prazosin or related quinazolines.
## Adverse Effects
* **Common:** Dizziness, headache, drowsiness, postural hypotension (especially with first dose), weakness.
* **Serious:** Syncope (especially first-dose phenomenon), priapism, erectile dysfunction.
## Key Drug Interactions
* **Other Antihypertensives:** Additive hypotensive effects.
* **Diuretics:** Increased risk of hypotension.
* **Beta-blockers:** May increase risk of severe hypotension.
* **Phosphodiesterase-5 Inhibitors (e.g., sildenafil):** Significant additive hypotensive effect. Co-administration is generally not recommended.
## Monitoring
* Blood pressure (supine and standing) before and during therapy, especially after dose changes.
* Monitor for signs/symptoms of syncope or severe dizziness.
* Assess effectiveness for PTSD nightmares.
## Clinical Pearls
* The "first-dose phenomenon" is a significant risk, characterized by severe postural hypotension and syncope within 1-2 hours of the first dose. Advise patients to take the first dose at bedtime and to avoid driving or operating machinery until they know how the medication affects them.
* Slow titration is crucial to minimize adverse effects, particularly dizziness and syncope.
* For PTSD, trazodone is often considered first-line; prazosin is an alternative if trazodone is ineffective or not tolerated.
* Take the medication consistently, preferably at the same times each day.
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*Disclaimer: This information is intended for educational purposes and does not substitute for professional medical advice. Always consult current prescribing information and a qualified healthcare provider for definitive guidance.*
