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# Prazosin
## Overview
Prazosin is an alpha-1 adrenergic blocker.
## Primary Indications
* Hypertension
* Symptomatic benign prostatic hyperplasia (BPH)
* Off-label: PTSD nightmares
## Adult Dosing
* **Hypertension:** Start at 1 mg orally twice daily or three times daily. Titrate slowly upwards based on blood pressure response. Usual maintenance dose: 3-20 mg per day, divided into two or three doses. Maximum recommended dose: 20 mg per day. Some sources suggest up to 40 mg per day may be used cautiously in refractory cases, but this is not standard.
* **Symptomatic BPH:** Start at 1 mg orally twice daily. Titrate slowly upwards based on symptom response. Usual maintenance dose: 1-5 mg per day, divided into two doses. Maximum recommended dose: 10 mg per day.
* **PTSD Nightmares:** Start at 1 mg orally at bedtime. Titrate upwards by 1 mg per week as needed and tolerated. Typical doses range from 1-8 mg per day, usually given at bedtime. Doses up to 16 mg per day have been reported.
## Pediatric Dosing
Dosing in pediatric patients is not well-established and should be determined by a specialist. Doses are generally lower and started with caution.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustment is routinely recommended, but caution and careful monitoring of blood pressure and side effects are advised, especially in severe impairment.
## Contraindications
* Hypersensitivity to prazosin or other quinazoline derivatives.
## Adverse Effects
* **Common:** Dizziness, headache, drowsiness, orthostatic hypotension (especially with first dose or dose increases), weakness, palpitations.
* **Serious:** Syncope (especially with the first dose), priapism, severe hypotension.
## Key Drug Interactions
* **Other Antihypertensives:** Additive hypotensive effects.
* **Beta-blockers:** Increased risk of profound hypotension and syncope, especially with initiation.
* **Diuretics:** Additive hypotensive effects.
* **PDE5 Inhibitors (e.g., sildenafil):** Increased risk of symptomatic hypotension and syncope. Avoid concomitant use or use with extreme caution and very low initial doses of PDE5 inhibitors.
## Monitoring
* Blood pressure (including orthostatic vital signs) at baseline and regularly during therapy, especially after dose adjustments.
* Signs and symptoms of BPH improvement.
* Patient-reported nightmares and sleep disturbance.
* Signs of syncope or severe dizziness.
## Clinical Pearls
* The "first-dose phenomenon" (marked orthostatic hypotension and syncope) is a significant concern. Advise patients to take the first dose at bedtime and avoid driving or hazardous activities for 12-24 hours after the first dose and after any dose increase.
* Dosing should be individualized and titrated slowly to minimize side effects, particularly orthostatic hypotension.
* Taking prazosin with food may reduce the incidence of orthostatic hypotension.
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*Disclaimer: This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant clinical guidelines before making treatment decisions. Dosing may vary based on individual patient factors and local protocols.*
