AB098. Can concomitant dutasteride reduce the effect of testosterone replacement therapy in men with late-onset hypogonadism? A 24-week, randomized, parallel study

OBJECTIVES: 5ARIs have sexual side effects, including erectile dysfunction (ED), loss of libido and ejaculatory dysfunction due to their action mechanism which decreases serum DHT levels. We examined whether concomitant dutasteride reduced the efficacy of testosterone replacement therapy (TRT) in men with late-onset hypogonadism. METHODS: This was a 24-week, randomized, parallel study of the clinical outcomes in men age >40 years with symptomatic benign prostatic hypertrophy [BPH; International Prostate Symptom Score (IPSS) th], prostate volume Prostate Symptom Score (IPSS) 300 ng/dL with aging male symptoms, who were taking stable doses of alpha-blockers 4 weeks before participation. Eligible patients received a combination of dutasteride 0.5 mg once daily and a transdermal gel containing 10 g testosterone (T) (DT group, n=30) or the transdermal gel alone (T group, n=30). The primary outcomes were the change in the aging male symptom (AMS) score, sexual desire (question 17, AMS score), and erectile function (International Index of Erectile Function-5). Secondary outcomes were the post-treatment IPSS, peak urinary flow rate, post-void residual urine volume (PVR), and prostate volume. RESULTS: Both groups showed significant improvements from baseline in all primary outcome parameters. However, there were no significant differences in the changes in the AMS total score (DT −5.2 vs. T −5.0; P=0.55), sexual desire (DT −2.5 vs. T −2.3; P=0.23), and IIEF-5 score (DT −2.1 vs. T −1.9; P=0.13) between groups. The extent of IPSS improvement from baseline to 24 weeks was the same in both groups (DT −1.2 vs. T −1.0; P=0.64). In addition, the changes in Q(max) and PVR from baseline were very similar in both groups. However, prostate volume decreased significantly (P<0.01) in the DT group (DT −6.1 cc vs. T +0.6 cc). CONCLUSIONS: Concomitant dutasteride did not reduce the effect of testosterone replacement therapy in men with late-2onset hypogonadism. Otherwise it would be helpful to prevent the progress of prostate size by TRT.