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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:**
* Initial dose: 1 mg orally twice daily.
* Titration: Increase dose gradually based on patient response, typically not exceeding 20 mg/day.
* Maintenance: 1 mg to 10 mg orally twice daily.
* Maximum: 20 mg/day. Doses up to 40 mg/day have been used but are not standard.
**Benign Prostatic Hyperplasia (BPH):**
* Initial dose: 1 mg orally twice daily.
* Titration: Gradually increase to 2 mg or 3 mg orally twice daily.
* Maintenance: 1 mg to 10 mg orally twice daily.
* Maximum: 20 mg/day.
**PTSD Nightmares (Off-label):**
* Dosing varies widely.
* Common starting dose: 1 mg orally at bedtime.
* Titration: May increase by 1 mg every 1-2 weeks, with doses up to 10 mg/day reported.
* Maximum: Doses typically do not exceed 10 mg/day.
## Pediatric Dosing
There is no established pediatric dosing for prazosin. Use in pediatric patients is generally off-label and requires careful consideration.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustment is typically required, but monitor closely for increased adverse effects.
## Contraindications
* Hypersensitivity to prazosin or other quinazoline derivatives.
## Adverse Effects
* **Orthostatic Hypotension/First-Dose Phenomenon:** Significant drop in blood pressure upon initiation or dose increase, leading to dizziness, lightheadedness, or syncope. This is most pronounced with the first dose and with rapid titration.
* Dizziness
* Headache
* Drowsiness
* Nausea
* Palpitations
* Weakness
* Nasal congestion
## Key Drug Interactions
* **Other Antihypertensives:** Additive hypotensive effects.
* **Diuretics:** Increased risk of hypotension.
* **PDE-5 Inhibitors (e.g., sildenafil):** Potentiation of hypotensive effects. Avoid concurrent use or use with caution and at lower doses.
* **Beta-blockers:** May exacerbate orthostatic hypotension.
## Monitoring
* **Blood Pressure:** Regularly monitor blood pressure, especially after initiation and dose changes. Assess for orthostatic hypotension (lying, sitting, and standing).
* **Symptoms:** Assess for dizziness, lightheadedness, and syncope.
## Clinical Pearls
* **First-Dose Effect:** Advise patients to take the first dose at bedtime to minimize the risk of syncope.
* **Gradual Titration:** Emphasize slow upward titration to improve tolerability and minimize orthostatic hypotension.
* **Timing of Doses:** For hypertension, doses are typically divided twice daily. For BPH, doses are also typically divided twice daily.
* **Tolerance:** Tolerance to the hypotensive effects can develop over time.
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*This information is intended for educational purposes and does not substitute for current prescribing information. Always consult official drug labeling and clinical guidelines before making therapeutic decisions.*
