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# Prazosin
## Overview
Prazosin is an alpha-1 adrenergic blocker.
## Primary Indications
* Hypertension (less commonly used now due to newer agents)
* Symptomatic Benign Prostatic Hyperplasia (BPH)
* Off-label: PTSD-related nightmares, Raynaud's phenomenon
## Adult Dosing
### Hypertension
* **Starting Dose:** 1 mg orally twice daily.
* **Maintenance Dose:** Titrate slowly based on blood pressure response, typically every 4-6 weeks. Usual range is 1 mg to 5 mg orally twice daily.
* **Maximum Dose:** 20 mg orally daily (divided into two doses).
### Benign Prostatic Hyperplasia (BPH)
* **Starting Dose:** 1 mg orally twice daily.
* **Maintenance Dose:** Titrate slowly based on symptom improvement. Usual range is 1 mg to 5 mg orally twice daily.
* **Maximum Dose:** 20 mg orally daily (divided into two doses).
### PTSD-related Nightmares (Off-label)
* **Starting Dose:** 1 mg orally at bedtime.
* **Maintenance Dose:** Titrate slowly based on symptom reduction. Typical doses range from 2 mg to 10 mg orally at bedtime, but doses up to 16 mg have been reported.
## Pediatric Dosing
There is no established pediatric dosing for prazosin. Use in pediatric populations is generally off-label and should be guided by expert consultation and a careful risk-benefit assessment.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustment is typically recommended, but caution and close monitoring of blood pressure are advised.
* **Hepatic Impairment:** No specific dose adjustment is typically recommended, but caution and close monitoring are advised.
## Contraindications
* Hypersensitivity to prazosin or other quinazolines.
## Adverse Effects
* **Most Common:** Dizziness, lightheadedness, drowsiness, headache, fatigue, nausea.
* **Orthostatic Hypotension:** Significant risk, especially with the first dose and with dose increases. This can lead to syncope ("first-dose syncope").
* **Priapism:** Rare but serious adverse effect.
* **Fluid retention:** Can occur, particularly when used for BPH.
## Key Drug Interactions
* **Antihypertensives:** Additive hypotensive effects. Monitor blood pressure closely.
* **Diuretics:** Additive hypotensive effects.
* **Beta-blockers:** May exacerbate orthostatic hypotension.
## Monitoring
* **Blood Pressure:** Regularly, especially after initiating therapy, with dose increases, and in patients with comorbidities. Monitor for orthostatic changes.
* **Symptoms:** For BPH, monitor urinary symptoms. For PTSD, monitor nightmare frequency and severity.
## Clinical Pearls
* Administer the first dose at bedtime or with the patient in a recumbent position to minimize the risk of severe orthostatic hypotension and syncope.
* Advise patients to avoid driving or operating heavy machinery until they know how prazosin affects them.
* Advise patients to rise slowly from a sitting or lying position.
* Prazosin is often used as a "drug of last resort" for PTSD-related nightmares when other treatments have failed.
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*Please verify current prescribing information for complete details and any updates.*
