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# Prazosin
## Overview
Prazosin is an alpha-1 adrenergic blocker used primarily for hypertension and off-label for PTSD-related nightmares.
## Primary Indications
* Hypertension
* Symptomatic treatment of PTSD-related nightmares
## Adult Dosing
* **Hypertension:** Start at 1 mg orally twice daily. Titrate slowly based on blood pressure response, usually every 2-4 days. Usual maintenance dose: 3-10 mg orally twice daily. Maximum dose: 20 mg orally twice daily.
* **PTSD-related nightmares:** Start at 1-5 mg orally at bedtime. May increase by 1-5 mg every 1-2 weeks as tolerated and based on symptom response. Usual dose: 4-10 mg orally at bedtime. Maximum dose: 10 mg orally at bedtime (though some sources may suggest higher, caution is advised).
## Pediatric Dosing
Prazosin is **not FDA-approved** for pediatric use. Limited case reports and small studies suggest potential use for hypertension or specific conditions like neuroleptic-induced akathisia, but established pediatric dosing is lacking. Dosing should be guided by specialist consultation and careful individual titration, often starting at very low doses (e.g., 0.1 mg/kg/day divided every 6-12 hours for hypertension) with extreme caution.
## Dose Adjustments
* **Hepatic Impairment:** Use with caution; no specific dose adjustments are established, but a lower starting dose and slower titration may be prudent.
* **Renal Impairment:** No specific dose adjustments are established.
## Contraindications
* Known hypersensitivity to prazosin or related quinazolines.
## Adverse Effects
* **Common:** Dizziness, drowsiness, headache, lightheadedness, orthostatic hypotension (especially with the first dose), nausea.
* **Serious:** Syncope (especially with first dose or dose increases), priapism, blurred vision, dyspnea.
## Key Drug Interactions
* **Other Antihypertensives:** Additive hypotensive effects.
* **Beta-Blockers:** May increase the risk of severe orthostatic hypotension.
* **Diuretics:** Additive hypotensive effects.
* **Phosphodiesterase-5 (PDE5) Inhibitors (e.g., sildenafil):** Significant additive hypotensive effects and increased risk of syncope. Separate administration or use with extreme caution.
## Monitoring
* **Blood Pressure:** Regularly monitor blood pressure, especially after initiation, dose increases, and in patients with other antihypertensives. Assess orthostatic vital signs (lying, sitting, standing) at baseline and during titration.
* **Symptoms of Hypotension:** Counsel patients on symptoms of dizziness and lightheadedness and instruct them to rise slowly.
* **PTSD Symptom Response:** If used for nightmares, assess the frequency and severity of nightmares.
## Clinical Pearls
* The "first-dose phenomenon" (severe orthostatic hypotension and syncope) is a significant concern. 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 PTSD-related nightmares, prazosin is generally considered most effective when administered at bedtime.
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*This information is intended for healthcare professionals. Always verify current prescribing information and consult relevant guidelines and resources before making clinical decisions.*
