Abstract: We included eight randomised controlled trials with 1699 participants across three comparisons. This abstract focuses on the primary outcomes of this review only. Scheduled phosphodiesterase type 5 inhibitors (PDE5I) versus placebo or no treatment Scheduled PDE5I may have little or no effect on short-term (up to 12 months) self-reported potency (risk ratio (RR) 1.13, 95% confidence interval (CI) 0.91 to1.41; very low quality evidence), which corresponds to 47 more men with self-reported potency per 1000 (95% CI 33 fewer to 149 more) and short-term erectile function as assessed by a validated instrument (RR 1.11, 95% CI 0.80 to 1.55; very low quality evidence), which corresponds to 28 more men per 1000 (95% CI 50 fewer to 138 more), but we are very uncertain of both of these findings. Scheduled PDE5I may result in fewer serious adverse events compared to placebo (RR 0.32, 95% CI 0.11 to 0.94; low quality evidence), though this does not appear biologically plausible and may represent a chance finding. We are also very uncertain of this finding. We found no long-term (longer than 12 months) data for any of the three primary outcomes. Scheduled PDE5I versus on-demand PDE5I Daily PDE5I appears to result in little to no difference in both short-term and long-term (greater than 12 months) self-reported potency (short term: RR 0.97, 95% CI 0.62 to 1.53; long term: RR 1.00, 95% CI 0.60 to 1.67; both very low quality evidence); this corresponds to nine fewer men with self-reported short-term potency per 1000 (95% CI 119 fewer to 166 more) and zero fewer men with self-reported long-term potency per 1000 (95% CI 153 fewer to 257 more). We are very uncertain of these findings. Daily PDE5I appears to result in little to no difference in short-term and long-term erectile function (short term: RR 1.00, 95% CI 0.65 to 1.55; long term; RR 0.74, 95% CI 0.48 to 1.14; both very-low quality evidence), which corresponds to zero men with short-term erectile dysfunction per 1000 (95% CI 80 fewer to 125 more) and 119 fewer men with long-term erectile dysfunction per 1000 (95% CI 239 fewer to 64 more). We are very uncertain of these findings. Scheduled PDE5I may result in little or no effects on short-term adverse events (RR 0.69 95% CI 0.12 to 4.04; very low quality evidence), which corresponds to seven fewer men with short-term serious adverse events (95% CI 18 fewer to 64 more), but we are very uncertain of these findings. We found no long-term data for serious adverse events. Scheduled PDE5I versus scheduled intraurethral prostaglandin E1 At short-term follow-up, daily PDE5I may result in little or no effect on self-reported potency (RR 1.10, 95% CI 0.79, to 1.52; very low quality evidence), which corresponds to 46 more men per 1000 (95% CI 97 fewer to 241 more). Daily PDE5I may result in a small improvement of erectile function (RR 1.64, 95% CI 0.84 to 3.20; very low quality evidence), which corresponds to 92 more men per 1000 (95% CI 23 fewer to 318 more) but we are very uncertain of both these findings. We found no long-term (longer than 12 months) data for any of the three primary outcomes. We found no evidence for any other comparisons and were unable to perform any of the preplanned subgroup analyses based on nerve-sparing approach, age or baseline erectile function. Based on mostly very-low and some low-quality evidence, penile rehabilitation strategies consisting of scheduled PDE5I use following radical prostatectomy may not promote self-reported potency and erectile function any more than on demand use.

Plain-language summary: We included eight randomised studies (clinical studies where people are randomly put into one of two or more treatment groups) with 1699 participants. Five trials compared the scheduled use of phosphodiesterase inhibitors (a type of medicine) to either no treatment or a placebo (a pretend drug with no effect). Two studies compared the use of phosphodiesterase inhibitors either as a daily prescription or as needed. One study compared the daily use of either a phosphodiesterase inhibitor or a medicine called prostaglandin E1 that is placed into the tip of the penis like a suppository. The main outcomes of this review that we felt were most important to men were how good they thought their erections were (self-reported potency), how good their erections were based on a specialised erection questionnaire (quality of erections) and any whether there were any major unwanted side effects. We found that the men who used these medicines on a scheduled basis may have had similar self-reported erections and quality of erections (based on questionnaires they filled out) as men who took no medication regularly or use it as needed. They also had similar rates of serious unwanted side effects and similar rates of stopping the drug before the end of the treatment duration. However, we are very uncertain of these findings. We were unable to research whether these results would be different in different groups of men based on whether the surgeon tried to preserve the nerves that help with erections or not, based on men's age and how good their erections were beforehand because we found no studies. The quality of evidence was very low for most main outcomes. That means we are very uncertain of the results of this review. Further research will likely change these findings.