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Abstract Background Based on our observations at the largest outpatient urology clinic in Iran, patients for whom finasteride is prescribed as a secondary drug to tamsulosin tend to experience earlier and more severe sexual side effects without any difference in the amelioration of symptoms. This study aimed to compare the time lag, efficacy, and side effects of combination therapy with varying doses of dutasteride or finasteride added to tamsulosin for benign prostatic hyperplasia (BPH) treatment. Methods In this study 165 were randomized into 5 groups (each N = 33); receiving tamsulosin 0.4mg plus either of A: finasteride 3mg, B: placebo, C: dutasteride 0.25mg, D: finasteride 5mg or E: dutasteride 0.5mg. During the 6-month period of the study, International Prostate Symptom Score (IPSS), post-void residual urine (PVR), International Index of Erectile Function (IIEF-5), prostate volume (PV), prostate specific antigen (PSA) and maximum urinary flow rate (Qmax) were evaluated at baseline and at the 1st, 3rd and 6th month. The differences between each time point and baseline were then compared between groups. Results At 3-month follow-up, group E exhibited a higher decrease in PSA but a greater increase in Qmax compared to group A ( p = 0.047 and 0.006, respectively). Group C showed higher Qmax increase compared to group A at 3 and 6 months ( p = 0.003 and 0.014) and concurrently a more pronounced PV decrease at 1 and 3 months ( p = 0.047 and 0.003, respectively). Group D had a significantly more decrease in their IIEF-5 compared to group A at one-month visit ( p = 0.006). Conclusions In summary, at the sixth-month follow-up, dutasteride demonstrated superiority over finasteride solely in enhancing Qmax. Therefore, dutasteride may be marginally more beneficial as a secondary component of combination therapy in BPH. Trial registration IRCT, IRCT20120516009772N2. Registered 18 January 2021 Retrospectively registered, https://irct.behdasht.gov.ir/search/result?query=IRCT20120516009772N2 .
Basiri et al. (Mon,) studied this question.