Reviews for Primary Care - Fall 2007 - (Page 6) Alpha Blockers for BPH Treatment continued Table 5 Doxazosin: Adverse Effects41 Doxazosin (n 665) Dizziness (includes vertigo) Fatigue Hypotension Edema Dyspnea 15.6% 8.0% 1.7% 2.7% 2.6% Placebo (n 300) 9.0% 1.7% 0.0% 0.7% 0.3% 1d subtypes. The modest receptor selectivity of tamsulosin is not sufficient to result in a clinically meaningful advantage. Typically, clinical advantages attributed to pharmacological selectivity require a receptor selectivity well beyond the tenfold difference observed with tamsulosin. Two pivotal trials of tamsulosin supported the NDA for the treatment of symptomatic BPH.47,48 Both 0.4 and 0.8 mg of tamsulosin achieved clinically significant improvements in symptom scores and peak flow rate (Figure 3, Table 6). The ability of the 0.4 mg tamsulosin dose to achieve a clinically significant effect without the requirement for dose titration represented a unique advantage over the other approved alpha blockers. Although a 0.8 mg daily dose was more effective than 0.4 mg, it did not gain popularity because it required both dose titration and taking 2 tablets of 0.4 mg. (A 0.8 mg tablet was not commercially available.) The primary reason tamsulosin was prescribed over terazosin and doxazosin was not due to greater efficacy or better tolerability, but simply the lack of dose titration. The prescribing community placed a greater value on eliminating the dose response at the expense of increasing the incidence of ejaculatory dysfunction, which was thought to be retrograde ejaculation as a result of relaxation of the bladder neck. Recent studies have demonstrated Table 6 Tamsulosin: Adverse Effects49 0.4 mg (n 501) Dizziness Abnormal ejaculation Asthenia/fatigue Libido decreased Amblyopia 14.9% 8.4% 7.8% 1.0% 0.2% 0.8 mg (n 492) 17.1% 18.1% 8.5% 2.0% 2.0% Placebo (n 493) 10.1% 0.2% 5.5% 1.2% 0.4% Figure 3. The effect of tamsulosin on lower urinary tract symptoms and peak flow rate relative to placebo.49 Qmax, peak urinary flow. Tamsulosin .08 mg Mean Change in Qmax (mL/s) 2 1.78* 1.75* 1.79* 1.52* Tamsulosin .04 mg Mean Change in Symptom Score 0 2 4 6 8 Placebo 3.60 5.5 8.3* 5.1* 5.8* 1 0.52 0.93 10 12 9.6* Study 1 (13 week) Study 2 (13 week) N 1486 0 Study 1 (13 week) Study 2 (13 week) *P .05 statistically significant difference from placebo. 6 VOL. 1 NO. 1 2007 REVIEWS FOR PRIMARY CARE
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