Doxazosin for benign prostatic hyperplasia in primary care

A randomized, double-blind crossover study of tamsulosin and controlled-release doxazosin in patients with benign prostatic hyperplasia

OBJECTIVE

To compare the effects of the doxazosin gastrointestinal therapeutic system, extended-release (doxazosin-GITS) formulation, and tamsulosin, another alpha1-antagonist, on total International Prostate Symptom Score (IPSS) and maximum urinary flow rate (Qmax) in treating patients with benign prostatic hyperplasia (BPH).

PATIENTS AND METHODS

Data were analysed from a prospective, randomized, double-blind, crossover study of men aged 50-80 years with concomitant BPH and hypertension as inclusion criteria. Fifty-two men were treated in four phases: phase I, placebo run-in for 2 weeks; phase II, first study drug doxazosin-GITS or tamsulosin for 8 weeks; phase III, washout with placebo for 2 weeks; and phase IV, second study drug tamsulosin or doxazosin-GITS for 8 weeks. Doxazosin-GITS was started at 4 mg/day and tamsulosin at 0.4 mg/day, and then titrated to 8 mg/day and 0.8 mg/day, respectively, after 4 weeks of therapy if the increase in Qmax was < 3 mL/s or the reduction in total IPSS was < 30%. Efficacy assessments included the IPSS and Qmax. Changes in blood pressure were not analysed, as most patients were actually not hypertensive. Endpoint efficacy data were analysed using an analysis of covariance model, with terms for sequence, phase, patients and sequence within patients, in addition to the baseline as covariate. Forty-seven men were treated in both efficacy arms of the study and were evaluable for analysis.

RESULTS

Doxazosin-GITS and tamsulosin significantly relieved lower urinary tract symptoms and significantly increased Qmax from baseline (P = 0.001). Doxazosin-GITS produced significantly greater improvements than tamsulosin in total IPSS (P = 0.019) and obstructive subscores (P = 0.004) at the last treatment visit. The difference between doxazosin-GITS and tamsulosin in improving Qmax approached significance in favour of the former (mean change from baseline 2.6 vs 1.7 mL/s, respectively; between-group difference P = 0.089). Both treatments were well tolerated.

CONCLUSIONS

Treatment with doxazosin-GITS was significantly more effective than tamsulosin in relieving lower urinary tract symptoms.

Hypertension in the elderly with coexisting benign prostatic hyperplasia

The treatment of hypertension in the elderly can be safely achieved with low-dose diuretic therapy. Men with prostatism may benefit from peripheral alpha-blocking drugs. However, drugs such as doxazosin or terazosin may further lower blood pressure and at times may be associated with orthostatic hypotension, especially if diuretics are given concomitantly. Tamsulosin achieves relaxation of the smooth muscle of the prostate, as do terazosin and doxazosin, but without provoking changes in blood pressure, especially orthostatic hypotension. There appears to be no adverse interaction with any other antihypertensive medication or with low-dose diuretics. To manage such patients with hypertension and prostatism, hydrochlorothiazide 6.25 to 12.5 mg/day and tamsulosin 0.4 mg/day would be an adequate combination. Low-dose diuretics have been shown to be effective in both isolated systolic hypertension as well as fixed diastolic hypertension in the elderly. If other antihypertensives need to be added, then a low dose of a long-acting calcium-entry blocker, a central alpha-agonist (a transdermal clonidine for better compliance), an angiotensin-converting enzyme inhibitor (if renal vascular disease has been ruled out), or an angiotensin II receptor blocker, e.g., losartan or valsartan, should be considered.