Prazosin for Hypertension and Benign Prostatic Hyperplasia
Prazosin is not recommended for treating benign prostatic hyperplasia (BPH), while for hypertension it can be initiated at 1 mg two to three times daily and titrated up to a maximum of 20 mg daily in divided doses. 1, 2
Use in Hypertension
Prazosin is an alpha-1 adrenergic blocker that can be used for treating hypertension with the following dosing protocol:
- Initial dose: 1 mg two or three times daily 2
- Maintenance dose: Can be slowly increased to a total daily dose of 20 mg in divided doses 2
- Typical effective range: 6-15 mg daily in divided doses 2
- Maximum dose: 20 mg daily (doses higher than this rarely increase efficacy) 2
- Dosing frequency: After initial titration, some patients can be maintained on a twice-daily regimen 2
Dosage Adjustments
- When adding a diuretic or other antihypertensive agent, reduce prazosin dose to 1-2 mg three times daily and then retitrate 2
- When used with PDE-5 inhibitors, the PDE-5 inhibitor should be initiated at the lowest dose due to potential additive hypotensive effects 2
Monitoring
- Blood pressure should be monitored regularly
- First-dose effect: The initial dose may cause significant hypotension, so the first dose should be taken at bedtime (see warnings) 2
Use in Benign Prostatic Hyperplasia
Prazosin is not recommended for BPH treatment based on current guidelines. The American Urological Association explicitly states that "data are insufficient to support a recommendation for the use of prazosin" for lower urinary tract symptoms (LUTS) secondary to BPH 1.
Preferred Alpha Blockers for BPH
The following alpha blockers are recommended instead:
- Alfuzosin
- Doxazosin
- Tamsulosin
- Terazosin 1
These agents have been extensively investigated and are considered to have equal clinical effectiveness for BPH treatment, though with slightly different adverse event profiles 1.
Evidence from Older Studies
While some older research studies from 1990 suggested that prazosin might be effective for BPH symptoms 3, 4, 5, 6, these findings have been superseded by more recent guidelines that favor other alpha blockers. A comparative study found that terazosin produced significantly higher improvement in BPH symptoms than tamsulosin, while prazosin showed some efficacy but is not preferred in current practice 7.
Common Side Effects and Precautions
- Orthostatic hypotension: Particularly with first dose or dose increases
- Other common side effects: Dizziness, tiredness (asthenia), ejaculatory problems, nasal congestion 1
- Special precautions: In men with hypertension and cardiac risk factors, alpha blocker monotherapy may be associated with higher incidence of congestive heart failure 1
Important Clinical Considerations
- For BPH treatment, current guidelines recommend alfuzosin, doxazosin, tamsulosin, or terazosin instead of prazosin 1
- For patients with both hypertension and BPH, one of the recommended alpha blockers for BPH may be used, but separate management of hypertension may still be required 1
- 5-alpha-reductase inhibitors (finasteride, dutasteride) are appropriate for BPH patients with demonstrable prostatic enlargement 1, 8
The evidence clearly indicates that while prazosin remains an option for hypertension management, it should not be selected for BPH treatment when other more thoroughly studied alpha blockers are available.