Please check your internet connection and try again.
# Prazosin
## Overview
Prazosin is a selective alpha-1 adrenergic antagonist that causes both arterial and venous vasodilation. It is primarily used for anti-hypertensive therapy and off-label for PTSD-associated nightmares.
## Primary Indications
* Hypertension (HTN)
* Off-label: PTSD-associated insomnia and nightmares
* Off-label: Benign Prostatic Hyperplasia (BPH) - *clinical use declining in favor of more uro-selective agents*
## Adult Dosing
* **Hypertension:** Start 1 mg at bedtime to minimize first-dose syncope. Titrate slowly based on response. Usual maintenance: 6–15 mg/day in divided doses. Maximum: 20 mg/day.
* **PTSD-associated nightmares:** Start 1 mg at bedtime. Increase by 1–2 mg every few days as tolerated. Typical effective dose: 2–10 mg at bedtime.
## Pediatric Dosing
* **Hypertension (rarely used):** Start 0.05–0.1 mg/kg/day in 2–4 divided doses. Maximum dose is not well-established; range 0.5–10 mg/day.
* *Note: Pediatric use is highly dependent on institutional protocols and specialist oversight.*
## Dose Adjustments
* **Renal Impairment:** No specific adjustment required.
* **Hepatic Impairment:** Use caution; metabolized extensively by the liver. Start with the lowest possible dose and titrate slowly.
## Contraindications
* Hypersensitivity to prazosin or other quinazolines (e.g., terazosin, doxazosin).
* History of syncopal episodes related to micturition (if used for BPH).
## Adverse Effects
* **First-dose phenomenon:** Profound orthostatic hypotension and syncope occurring 30–90 minutes after the first dose.
* **Common:** Dizziness, headache, drowsiness, weakness, palpitations, and nausea.
* **Rare:** Priapism (requires immediate emergency intervention).
## Key Drug Interactions
* **PDE-5 Inhibitors (e.g., Sildenafil, Tadalafil):** Synergistic vasodilation; increased risk of symptomatic hypotension.
* **Antihypertensives:** Potential for additive hypotensive effects.
* **Alpha-blockers:** Concomitant use with other alpha-adrenergic blockers is not recommended.
## Monitoring
* **Blood Pressure:** Monitor standing and sitting/supine BP during dose initiation and titration.
* **Symptomatic Hypotension:** Assess for dizziness or lightheadedness, particularly during the first week of therapy or after dose increases.
## Clinical Pearls
* **First Dose:** Always administer the initial dose at bedtime to mitigate the risk of injury from orthostatic syncope.
* **Titration:** "Start low and go slow" is critical.
* **Counseling:** Advise patients to rise slowly from a sitting or lying position. If nighttime dosing causes excessive morning grogginess, consider splitting the dose.
* **Effectiveness:** In PTSD, it may take several weeks of dose titration to reach therapeutic efficacy for nightmares.
***
*Disclaimer: This information is for educational purposes only. Clinical protocols may vary by institution. Always consult the latest package insert, local formularies, or clinical decision support software before prescribing or administering medication.*
