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# Prazosin
## Overview
Prazosin is an alpha-1 adrenergic antagonist used for the treatment of hypertension and off-label for PTSD-related nightmares.
## Primary Indications
* Hypertension
* PTSD-related nightmares (off-label)
## Adult Dosing
* **Hypertension:** Start at 1 mg two to three times daily. Titrate slowly based on blood pressure response. Usual maintenance dose: 3 mg to 20 mg daily, divided into two or three doses. Maximum: 20 mg daily.
* **PTSD-related nightmares:** Start at 1 mg to 2 mg at bedtime. Titrate slowly. Usual maintenance dose: 4 mg to 10 mg at bedtime. Maximum: 10 mg at bedtime. Dosing for nightmares may be adjusted based on clinical response and local protocols.
## Pediatric Dosing
Dosing in pediatric patients is not well-established and should be guided by specialist consultation and careful titration. Some sources suggest starting doses for hypertension as low as 0.05 mg/kg/day divided every 6-12 hours.
## Dose Adjustments
* **Renal Impairment:** Use with caution. No specific dose adjustment is universally recommended, but reduced frequency or dose may be considered.
* **Hepatic Impairment:** Use with caution.
## Contraindications
* Known hypersensitivity to prazosin or other quinazolines.
## Adverse Effects
* **Common:** Dizziness, drowsiness, headache, orthostatic hypotension (especially with the first dose), lightheadedness, weakness, palpitations.
* **Serious:** Syncope (especially with first-dose or dose increases), priapism.
## Key Drug Interactions
* **Other Antihypertensives:** Additive hypotensive effect.
* **Diuretics:** Increased risk of orthostatic hypotension.
* **Beta-blockers:** May increase the risk of severe orthostatic hypotension.
* **Phosphodiesterase-5 (PDE5) Inhibitors (e.g., sildenafil, tadalafil):** Potentiation of hypotensive effects; avoid concomitant use if possible or monitor blood pressure closely.
## Monitoring
* Blood pressure (supine and standing) before and during treatment, especially after dose initiation or increases.
* Symptoms of dizziness, lightheadedness, or syncope.
* For PTSD nightmares: Assess nightmare frequency and severity.
## Clinical Pearls
* **First-dose phenomenon:** The initial dose can cause profound orthostatic hypotension and syncope. Advise patients to take the first dose at bedtime and avoid driving or operating machinery until they know how the medication affects them.
* Dose increases should be gradual.
* Advise patients to rise slowly from a sitting or lying position.
* For PTSD nightmares, prazosin is generally dosed at bedtime only.
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*Disclaimer: This information is intended for healthcare professionals. Always consult the official prescribing information and relevant clinical guidelines for complete details before making any clinical decisions. Dosing may vary based on individual patient factors, clinical judgment, and local protocols.*
