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## Prazosin
### Overview
Prazosin is an alpha-1 adrenergic blocker.
### Primary Indications
* Hypertension
* Symptomatic benign prostatic hyperplasia (BPH)
* Off-label: PTSD-related nightmares (often used in conjunction with therapy)
### Adult Dosing
* **Hypertension:** Initiate at 1 mg orally two to three times daily. Titrate slowly based on blood pressure response. Usual maintenance dose: 3 mg to 9 mg daily, divided into two or three doses. Maximum dose: 20 mg daily.
* **BPH:** Initiate at 1 mg orally two to three times daily. Titrate slowly based on symptom response. Usual maintenance dose: 2 mg to 5 mg daily, divided into two or three doses. Maximum dose: 10 mg daily.
* **PTSD Nightmares:** Initiate at 1 mg orally at bedtime. Titrate slowly based on nightmare frequency and severity. Usual dose: 3 mg to 10 mg at bedtime. Some sources suggest doses up to 16 mg daily.
### Pediatric Dosing
Prazosin is not FDA-approved for pediatric use. Limited data exists for off-label use in pediatric hypertension, typically initiated at very low doses (e.g., 0.05 mg/kg/day divided every 6-8 hours) and titrated cautiously.
### Dose Adjustments
* **Renal Impairment:** Caution advised. No specific dose reduction guidelines are established, but initiation at the lower end of the dosing range and slower titration may be warranted.
* **Hepatic Impairment:** No specific dose adjustment guidelines are established.
### Contraindications
* Known hypersensitivity to prazosin or related quinazolines.
### Adverse Effects
* **Common:** Dizziness, lightheadedness, headache, drowsiness, weakness, nausea, palpitations.
* **Serious:** Orthostatic hypotension, syncope (especially with first dose or dose increase), priapism.
### Key Drug Interactions
* **Other antihypertensives (e.g., diuretics, beta-blockers):** Additive hypotensive effect.
* **Vasodilators:** Increased risk of hypotension.
* **PDE5 inhibitors:** Potential for additive hypotensive effects.
### Monitoring
* Blood pressure (especially orthostatic vital signs) at initiation and after dose changes.
* Signs and symptoms of BPH, if indicated.
* Patient-reported symptoms and distress, if used for PTSD nightmares.
### Clinical Pearls
* **First-dose phenomenon:** Significant orthostatic hypotension and syncope can occur with the first dose or after a dose increase. Administer the first dose at bedtime and advise patients to avoid driving or operating machinery until they know how the medication affects them.
* Dosing should be individualized based on response and tolerability.
* For BPH, prazosin works by relaxing smooth muscle in the prostate and bladder neck.
* For PTSD nightmares, the exact mechanism is not fully understood, but it is thought to involve blocking norepinephrine release in the amygdala.
**Disclaimer:** This information is intended for clinical use and does not substitute for professional medical judgment. Always consult the most current prescribing information and relevant guidelines before making therapeutic decisions.
