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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
### Adult Dosing
* **Hypertension:** Initiate at 1 mg twice daily. Titrate slowly based on response, typically every 4-6 hours during initial titration. Usual maintenance dose: 1-5 mg two to three times daily. Maximum dose: 20 mg daily.
* **BPH:** Initiate at 1 mg twice daily. Titrate slowly. Usual maintenance dose: 1-5 mg two to three times daily. Maximum dose: 20 mg daily.
* **PTSD-related nightmares:** Initiate at 1 mg at bedtime. Titrate slowly based on response and tolerability. Usual dose: 1-10 mg at bedtime. Some protocols may go higher, but evidence for efficacy and safety above 10 mg is limited.
### Pediatric Dosing
* Dosing for pediatric patients is not well-established. Limited studies suggest starting at low doses (e.g., 0.1 mg/kg/day divided into 2-3 doses) for hypertension, but specific recommendations vary. Consultation with a pediatric specialist is recommended.
### Dose Adjustments
* **Renal impairment:** Use with caution. No specific dose reduction guidelines, but lower doses and slower titration may be necessary.
* **Hepatic impairment:** Use with caution.
### Contraindications
* Known hypersensitivity to prazosin or other quinazolines.
### Adverse Effects
* **Common:** Dizziness, lightheadedness, drowsiness, headache, weakness, nausea.
* **Serious:** Orthostatic hypotension (especially with first dose or dose increases), syncope. Fluid retention can occur.
### Key Drug Interactions
* **Other antihypertensives:** Additive hypotensive effects.
* **Beta-blockers:** Increased risk of severe orthostatic hypotension.
* **Diuretics:** Additive hypotensive effects.
* **Vasodilators (e.g., nitrates):** Potentiated hypotensive effect.
* **Erectile dysfunction medications (e.g., PDE5 inhibitors):** Significant risk of severe hypotension and syncope. Avoid concurrent use or use with extreme caution and very low doses.
### Monitoring
* Blood pressure (supine and standing) at initiation and with dose changes, especially within the first few hours of the first dose and with subsequent dose titrations.
* Monitor for signs and symptoms of orthostatic hypotension (dizziness, lightheadedness, falls).
* Assess for fluid retention (edema, weight gain).
### Clinical Pearls
* **First-dose phenomenon:** Significant orthostatic hypotension and syncope can occur with the first dose or with rapid increases in dose. Advise patients to take the first dose at bedtime and avoid driving or hazardous activities until they know how the medication affects them.
* Titration should be slow and cautious, particularly in elderly patients or those with other cardiovascular conditions.
* Prazosin is generally not the first-line agent for hypertension but may be useful in specific populations or as add-on therapy.
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*This information is intended for healthcare professionals. Always consult the official prescribing information and current clinical guidelines for complete details and to confirm suitability for individual patients.*
