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# Prazosin
## Overview
Prazosin is an alpha-1 adrenergic blocker.
## Primary Indications
* Hypertension
* Off-label: PTSD nightmares, Raynaud's phenomenon, benign prostatic hyperplasia (BPH) symptoms
## Adult Dosing
* **Hypertension:** Start at 1 mg orally at bedtime. Titrate slowly upwards every 2-4 days based on blood pressure response and tolerability. Typical maintenance doses range from 3 mg to 20 mg per day, divided into 2 or 3 doses. Maximum dose: 20 mg/day (some sources cite up to 40 mg/day, but efficacy and safety beyond 20 mg/day are less established).
* **PTSD Nightmares:** Start at 1 mg orally at bedtime. Can be increased by 1 mg increments per week as needed and tolerated. Target doses typically range from 2 mg to 6 mg per day, usually taken at bedtime. Some patients may require higher doses.
* **Raynaud's Phenomenon:** Starting dose 1 mg orally twice daily. Titrate to 2 mg orally three times daily.
* **BPH Symptoms:** Not a first-line agent. If used, typical doses are 0.5 mg to 2 mg orally twice daily.
## Pediatric Dosing
* There is no established standard pediatric dosing for prazosin. Dosing in children is generally based on limited case reports and clinical experience.
* **Hypertension (off-label):** Doses reported range from 0.1 mg/kg/day to 0.5 mg/kg/day divided into 2-3 doses. Maximum dose not well established, but generally limited by adverse effects.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustment is typically recommended, but caution and slow titration are advised due to potential accumulation.
* **Hepatic Impairment:** Use with caution.
## Contraindications
* Hypersensitivity to prazosin or other quinazolines.
## Adverse Effects
* **Most Common:** Dizziness, drowsiness, headache, orthostatic hypotension (especially with the first dose and with dose increases).
* **Other:** Palpitations, nausea, blurred vision, dry mouth, edema.
* **Serious:** Syncope (especially with first-dose phenomenon), priapism (rare but serious).
## Key Drug Interactions
* **Antihypertensives:** Additive hypotensive effects.
* **Diuretics:** Additive hypotensive effects.
* **Beta-blockers:** May increase risk of severe orthostatic hypotension.
* **Vasodilators:** Additive hypotensive effects.
## Monitoring
* Blood pressure (especially orthostatic vital signs after initiation and dose increases).
* Symptoms of dizziness or syncope.
* Renal and hepatic function (periodically).
## Clinical Pearls
* The "first-dose phenomenon" can cause profound orthostatic hypotension and syncope, especially with the first dose or with rapid dose escalation. Advise patients to take the first dose at bedtime and to avoid driving or operating hazardous machinery for the first few doses.
* Advise patients to rise slowly from a sitting or lying position.
* Tolerance to the vasodilatory effects may develop over time.
* Prazosin is available as a capsule and an oral concentrate. The oral concentrate may be more appropriate for very small doses in children or for slow titration.
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*Please consult the most current prescribing information for complete details and to ensure accuracy. This information is for educational purposes and does not replace professional medical advice.*
