From the Guidelines
Prazosin is effective as a second-line agent for treating high blood pressure and symptoms of benign prostatic hyperplasia (BPH), but its use should be considered with caution due to potential side effects such as orthostatic hypotension. According to the 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA guideline for the prevention, detection, evaluation, and management of high blood pressure in adults 1, prazosin is listed as a secondary agent with a usual dose range of 2-20 mg, taken 2 or 3 times daily. The guideline notes that alpha-1 blockers like prazosin may be considered as second-line agents in patients with concomitant BPH. However, the AUA guideline on management of BPH (2003) states that data are insufficient to support a recommendation for the use of prazosin as a treatment option for LUTS secondary to BPH 1.
Some key points to consider when prescribing prazosin include:
- Starting with a low dose, such as 1mg at bedtime, to minimize the risk of orthostatic hypotension
- Gradually increasing the dose as needed and tolerated
- Monitoring patients for signs of orthostatic hypotension, such as dizziness or lightheadedness, especially after the first dose or when increasing the dosage
- Considering alternative treatment options for patients with hypertension and cardiac risk factors, as doxazosin monotherapy has been associated with a higher incidence of congestive heart failure compared to other antihypertensive agents 1.
Overall, while prazosin can be an effective treatment option for certain patients, its use should be carefully considered and monitored to minimize potential side effects and ensure optimal management of hypertension and BPH symptoms.
From the FDA Drug Label
The results confirm that the therapeutic effect is a fall in blood pressure unaccompanied by a clinically significant change in cardiac output, heart rate, renal blood flow and glomerular filtration rate In man, blood pressure is lowered in both the supine and standing positions. This effect is most pronounced on the diastolic blood pressure Tolerance has not been observed to develop in long term therapy In clinical studies to date, prazosin hydrochloride has not increased plasma renin activity.
Prazosin is effective in lowering blood pressure, as evidenced by its ability to decrease diastolic blood pressure in both supine and standing positions, without significant changes in cardiac output, heart rate, renal blood flow, and glomerular filtration rate 2.
- The therapeutic effect of prazosin is a fall in blood pressure.
- Tolerance has not been observed to develop in long-term therapy.
- Prazosin does not have a negative chronotropic effect or increase plasma renin activity.
From the Research
Effectiveness of Prazosin
- Prazosin has been shown to be an effective antihypertensive agent over the entire range of hypertension, when used alone or in multitherapy 3.
- It is particularly useful in specific subpopulations of hypertensive patients, such as those with impaired renal function, those on hemodialysis, and those with concomitant heart block, bronchospasm, diabetes mellitus, or disturbed carbohydrate metabolism, hyperlipidemia, or hyperuricemia 3.
- Prazosin is also effective in reducing symptoms of benign prostatic hyperplasia (BPH), with 60-70% of treated patients experiencing real benefits from prazosin therapy 4.
Comparison with Other Alpha-Blockers
- Prazosin has been compared to other alpha-blockers, such as terazosin and tamsulosin, in the treatment of symptomatic BPH 5.
- The study found that terazosin produced significantly higher improvement in individual symptoms than tamsulosin, while prazosin and tamsulosin produced significant increases in maximum and average urinary flow rates 5.
- Tamsulosin has been shown to have a higher affinity for prostatic than vascular alpha 1-adrenoceptors, and does not reduce blood pressure at the doses used to relax prostatic smooth muscle 6, 7.