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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 and sleep disturbances
## Adult Dosing
**Hypertension:**
* Initiate at 1 mg orally twice daily.
* Titrate slowly based on blood pressure response, typically increasing by 1 mg every 2-3 days.
* Usual maintenance dose: 1 mg to 5 mg orally twice daily.
* Maximum dose: 20 mg orally daily (divided into two doses).
**Symptomatic BPH:**
* Initiate at 1 mg orally twice daily.
* Titrate slowly based on symptom response, typically increasing by 1 mg every 2-3 days.
* Usual maintenance dose: 2 mg orally twice daily.
* Maximum dose: 10 mg orally daily (divided into two doses).
**PTSD-related nightmares/sleep disturbances:**
* Initiate at 1 mg orally at bedtime.
* Titrate slowly based on symptom response, typically increasing by 1 mg every 1-2 weeks.
* Doses may range from 1 mg to 10 mg orally at bedtime.
## Pediatric Dosing
There is no established pediatric dosing for prazosin. Use is generally avoided due to lack of data.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustment is recommended, but caution and slower titration may be warranted due to potential for accumulation.
* **Hepatic Impairment:** Use with caution; no specific dose adjustment recommended.
## Contraindications
* Hypersensitivity to prazosin or other quinazolines.
## Adverse Effects
* **Common:** Dizziness, lightheadedness, headache, drowsiness, weakness, palpitations.
* **Orthostatic Hypotension:** Most significant and dose-limiting; particularly common with first dose or dose increases. Advise patients to take the first dose at bedtime and avoid sudden changes in posture.
* **Priapism:** Rare but serious.
* **Nasal congestion.**
## Key Drug Interactions
* **Other Antihypertensives:** Additive hypotensive effect.
* **Beta-blockers:** Increased risk of severe orthostatic hypotension, particularly with initial doses.
* **Diuretics:** Additive hypotensive effect.
* **Vasodilators:** Additive hypotensive effect.
## Monitoring
* Blood pressure (especially orthostatic vital signs) at initiation and with dose changes.
* Signs and symptoms of BPH if indicated.
* Sleep quality and nightmare frequency if indicated for PTSD.
## Clinical Pearls
* The "first-dose phenomenon" can cause profound syncope (loss of consciousness) and hypotension. Patients should be advised to take the first dose at bedtime and avoid driving or operating heavy machinery until they know how the medication affects them.
* Dosing should be titrated slowly, especially in elderly patients or those taking other antihypertensives.
* Prazosin is generally taken twice daily for hypertension, but once daily at bedtime may be sufficient for BPH or PTSD nightmares.
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*This information is intended for clinical pharmacists and should not replace a thorough review of the current prescribing information and patient-specific factors.*
