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# Prazosin
## Overview
Prazosin is an alpha-1 adrenergic blocker.
## Primary Indications
* Hypertension
* Symptomatic benign prostatic hyperplasia (BPH)
* Refractory PTSD nightmares (off-label)
## Adult Dosing
* **Hypertension:** Initiate at 1 mg orally twice daily. Titrate slowly based on blood pressure response, typically increasing by 1 mg every 1-2 weeks. Usual effective dose range is 3-20 mg daily, divided into two doses. Maximum dose is generally considered 20 mg daily, though some sources may suggest up to 40 mg daily in severe cases.
* **BPH:** Initiate at 1 mg orally twice daily. Titrate as tolerated to a usual dose of 2-5 mg orally twice daily. Maximum dose is 10 mg daily, divided into two doses.
* **PTSD Nightmares:** Initiate at 1 mg orally at bedtime. Titrate slowly, often to 4-10 mg orally at bedtime. Dosing is highly individualized and should be managed by a specialist.
## Pediatric Dosing
There is no established pediatric dosing for prazosin. Its use in children is generally off-label and should be guided by expert consultation and careful titration.
## Dose Adjustments
* **Renal Impairment:** Use with caution. No specific dose adjustment is usually recommended, but starting with a lower dose and titrating slowly may be prudent.
* **Hepatic Impairment:** Use with caution.
## Contraindications
* Known hypersensitivity to prazosin or other quinazoline derivatives.
## Adverse Effects
* **Common:** Dizziness, headache, drowsiness, orthostatic hypotension (especially with first dose or dose increase), weakness, palpitations.
* **Serious:** Syncope (especially with first dose syndrome), severe hypotension.
## Key Drug Interactions
* **Other antihypertensives:** Additive hypotensive effect.
* **Diuretics:** Increased risk of hypotension.
* **Beta-blockers:** Increased risk of orthostatic hypotension.
* **PDE-5 inhibitors (e.g., sildenafil):** Significant additive hypotensive effects; avoid concomitant use or use with extreme caution.
## Monitoring
* Blood pressure (including orthostatic measurements) prior to and during therapy.
* Monitor for signs and symptoms of syncope, especially after the first dose and with dose increases.
## Clinical Pearls
* The "first-dose phenomenon" can cause profound syncope and should be anticipated. Advise patients to take the first dose at bedtime and avoid driving or hazardous activities for the first dose and for 24 hours after any dose increase.
* Titrate slowly to minimize side effects, particularly dizziness and orthostatic hypotension.
* Prazosin's alpha-blocking effect can also relax smooth muscle in the bladder neck and prostate, contributing to its use in BPH.
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**Disclaimer:** This information is intended for clinical use and does not replace official prescribing information. Always verify current prescribing information and consult with a qualified healthcare professional before making any treatment decisions.
