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# Prazosin
## Overview
Prazosin is an alpha-1 adrenergic blocker.
## Primary Indications
* Hypertension
* Symptomatic Benign Prostatic Hyperplasia (BPH)
* Refractory nightmares associated with PTSD
## Adult Dosing
**Hypertension:**
* Initiate at 1 mg orally twice daily.
* Titrate gradually based on blood pressure response, typically increasing every 2-4 days.
* Usual effective dose: 3-15 mg orally per day, divided into two doses.
* Maximum dose: 20 mg orally per day.
* **First-dose phenomenon:** Patients may experience marked hypotension, syncope, and excessive drowsiness 30-90 minutes after the first dose or following a dose increase. Advise taking the first dose at bedtime.
**Symptomatic BPH:**
* Initiate at 1 mg orally twice daily.
* Titrate gradually based on symptom relief, typically increasing every 1-2 weeks.
* Usual effective dose: 2-5 mg orally twice daily.
* Maximum dose: 5 mg orally twice daily (total 10 mg/day).
**PTSD Nightmares:**
* Initiate at 1 mg orally at bedtime.
* Titrate gradually, often increasing by 1 mg every week or two.
* Doses can range from 1 mg to 10 mg orally per night.
* Dosing regimens vary; consult specific protocols or literature.
## Pediatric Dosing
Prazosin is generally **not recommended** for pediatric use in hypertension due to lack of established efficacy and safety data.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustment is typically required, but monitor blood pressure closely as clearance may be reduced.
* **Hepatic Impairment:** Use with caution.
## Contraindications
* Known hypersensitivity to prazosin or related quinazolines.
## Adverse Effects
* **Common:** Dizziness, headache, drowsiness, orthostatic hypotension (especially with first dose), palpitations, nausea.
* **Less Common:** Weakness, blurred vision, dry mouth, edema, syncope.
## Key Drug Interactions
* **Other Antihypertensives:** Additive hypotensive effects.
* **Beta-blockers:** May increase the risk of severe orthostatic hypotension.
* **Diuretics:** Additive hypotensive effects.
* **PDE5 Inhibitors (e.g., sildenafil):** Significantly increased risk of symptomatic hypotension and syncope. Avoid concurrent use or use with extreme caution and dose adjustment of one agent.
## Monitoring
* Blood pressure (supine and standing) before initiating therapy and regularly during treatment, especially after dose changes.
* Monitor for symptoms of dizziness, lightheadedness, and syncope.
* Assess for symptom relief in BPH and PTSD nightmares.
## Clinical Pearls
* The first-dose phenomenon is a critical safety concern. Counsel patients to take the first dose at bedtime and avoid activities requiring mental alertness until tolerance is established.
* Taper dose gradually if discontinuing therapy to avoid rebound hypertension.
* Can be used for hypertension in pregnancy, although not a first-line agent.
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*Disclaimer: This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant guidelines before making any clinical decisions.*
