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# Prazosin
## Overview
Prazosin is a selective alpha-1 adrenergic receptor antagonist.
## Primary Indications
* Hypertension
* Symptomatic Benign Prostatic Hyperplasia (BPH)
* Off-label: PTSD-related nightmares, Raynaud's phenomenon
## Adult Dosing
**Hypertension:**
* Initiate at 1 mg by mouth twice daily.
* Titrate up to a maximum of 10 mg by mouth twice daily, or 20 mg by mouth twice daily in some cases, depending on clinical response and tolerability. Dosing can be adjusted every 2-4 weeks.
**BPH:**
* Initiate at 1 mg by mouth twice daily.
* Titrate up to 2 mg by mouth twice daily. Maximum dose is typically 5 mg by mouth twice daily.
**PTSD-related nightmares:**
* Initiate at 1 mg by mouth at bedtime.
* Titrate as needed up to 10 mg by mouth at bedtime. Some protocols may use doses up to 16 mg/day divided twice daily.
## Pediatric Dosing
Dosing in pediatric patients is not well established and should be approached with caution, typically by specialists. Limited data suggests starting doses for hypertension might range from 0.5-2 mg/m²/day divided into 2-3 doses, with careful titration.
## Dose Adjustments
* **Hepatic Impairment:** Use with caution. Dose reduction may be necessary.
* **Renal Impairment:** No specific dose adjustment is typically recommended, but monitor closely for adverse effects, especially hypotension.
## Contraindications
* Hypersensitivity to prazosin or other quinazolines.
## Adverse Effects
* **Most Common:** Dizziness, drowsiness, headache, weakness, postural hypotension, palpitations.
* **Significant:** First-dose syncope (especially with initial doses or dose increases), severe hypotension.
## Key Drug Interactions
* **Other Antihypertensives (e.g., diuretics, beta-blockers):** Additive hypotensive effect.
* **Vasodilators:** Additive hypotensive effect.
* **PDE5 Inhibitors (e.g., sildenafil):** Increased risk of severe hypotension and syncope. Avoid concomitant use if possible, or separate administration by at least 4 hours.
## Monitoring
* Blood pressure (supine and standing) especially after initiating therapy and with dose changes.
* Symptoms of dizziness or syncope.
## Clinical Pearls
* Administer the first dose with caution, preferably at bedtime, due to the risk of first-dose syncope.
* Instruct patients to rise slowly from a sitting or lying position.
* Dosing frequency is typically twice daily for hypertension and BPH. Nightmares may be dosed once at bedtime.
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*This information is intended for healthcare professionals. Always consult the official prescribing information and relevant guidelines for the most up-to-date and comprehensive drug information.*
