Ten randomised controlled trials fulfilled the inclusion criteria (2123 men given sildenafil and 1131 placebo).

NNT or NNH were calculated for important efficacy, adverse event and discontinuation outcomes.
Dose optimisation led to at least 60% of attempts at sexual intercourse being successful in 49% of men, compared with 11% with placebo; the NNT was 2.7 (95% confidence interval 2.3 to 3.3).

For global improvement in erections the NNT was 1.7 (1.6 to 1.9). Treatment-related adverse events occurred in 30% of men on dose optimised sildenafil compared with 11% on placebo; the NNH was 5.4 (4.3 to 7.3).

All cause discontinuations were less frequent with sildenafil (10%) than with placebo (20%).

Sildenafil dose optimisation gave efficacy equivalent to the highest fixed doses, and adverse events equivalent to the lowest fixed doses.