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# Prazosin
## Overview
Prazosin is a selective alpha-1 adrenergic receptor antagonist.
## Primary Indications
* Hypertension
* Symptomatic benign prostatic hyperplasia (BPH)
* Off-label: PTSD-related nightmares (refractory)
## Adult Dosing
* **Hypertension:**
* Initial: 1 mg orally twice daily.
* Titration: Increase dose gradually every 2-4 days as needed.
* Maintenance: Typically 3-15 mg orally per day in 2-3 divided doses.
* Maximum: 20 mg orally per day.
* **Benign Prostatic Hyperplasia (BPH):**
* Initial: 1 mg orally twice daily.
* Maintenance: Typically 2-5 mg orally twice daily.
* Maximum: 10 mg orally per day in divided doses.
* **PTSD-related nightmares (refractory):**
* Dosing is highly individualized and may differ from hypertension protocols. Initiate at low doses and titrate slowly. An example starting dose is 1 mg at bedtime, with gradual increases up to 8 mg per day in divided doses. Specific protocols may vary.
## Pediatric Dosing
Prazosin is generally not recommended for pediatric hypertension due to lack of established dosing guidelines and availability of safer alternatives.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustment is universally recommended, but caution and careful titration are advised, especially with severe impairment.
* **Hepatic Impairment:** Use with caution.
## Contraindications
* Known hypersensitivity to prazosin or related quinazolines.
## Adverse Effects
* **Common:** Dizziness, drowsiness, headache, orthostatic hypotension, weakness, palpitations.
* **Serious:** Syncope (especially with first dose or dose increases), priapism.
## Key Drug Interactions
* **Antihypertensives:** Additive hypotensive effects.
* **Diuretics:** Additive hypotensive effects.
* **Beta-blockers:** Increased risk of severe orthostatic hypotension with the first dose of prazosin.
* **Vasodilators:** Additive hypotensive effects.
## Monitoring
* Blood pressure, especially orthostatic vital signs (lying/sitting vs. standing) within 1-3 hours after the first dose and with each dose increase.
* Renal and hepatic function.
* Signs of urinary retention (in BPH).
## Clinical Pearls
* The "first-dose phenomenon" can cause profound orthostatic hypotension and syncope, particularly with the first dose or after a dose increase. Advise patients to take the first dose at bedtime and avoid driving or operating machinery until they know how the medication affects them.
* Dosing should be individualized and titrated slowly.
* For BPH, therapeutic benefit may not be apparent for several weeks.
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*Please verify current prescribing information for any patient-specific decisions.*
