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erectile maintenance frequency, IIEF–Q4 (mean difference 1.34, 95 percent CI: 0.75–1.93);
erection, as assessed by GEQ–Q1 (RR = 3.07, 95 percent CI: 1.81–5.19); and percentage of
successful intercourse attempts (RR = 2.41, 95 percent CI: 1.99–2.92) (Figures 22–25).
A high degree of heterogeneity with respect to the proportion of patients with improved
erection (GEQ–Q1) was present across the two trials (I 2 = 83.2 percent) (Figure 24). Although
the effect size for the two estimates of the RR was in the same direction, the magnitude of this
effect differed between the two trials (2.33 143 versus 3.94 147 ). One explanation of this finding
could be the disparate rates of improvement on GEQ observed in the placebo arms of these trials
(29 percent 143 versus 18 percent 147 ). Note that the respective rates in the sildenafil arms were
quite similar (73 percent versus 71 percent). The higher rate of improvement on GEQ for the
placebo arm in the first trial 143 resulted in the smaller effect size (RR = 2.33). This could be
explained by a higher proportion of participants with a mild to moderate form of ED, which may
have resulted from the difference between the two trials in with respect to the use of inclusion
criteria based on IIEF scores (≤25 143 versus ≤21 147 ). Moreover, other contributing factors for the
observed differences for the improvement rates between the two placebo arms could have been
due to the fewer patients with organic ED (18 percent 143 versus 51 percent 147 ) and a shorter mean
duration of ED in the first trial (2.2 years 143 versus 4.5 years 147 ). The two trials employed similar
dosing regimens (from 50 mg to 25 mg or 100 mg) and duration of sildenafil treatment (6–8
weeks). 143,147
Harms. Incidence of any adverse event: headache, dyspepsia, flushing.
The pooled RR estimates showed a statistically significant increase in risk among
participants treated with sildenafil compared with those receiving placebo for all-cause adverse
events (RR = 1.72, 95 percent CI: 1.33–2.24) and for the treatment-related specific events such
as headaches (RR = 6.32, 95 percent CI: 1.92–20.85), dyspepsia (RR = 8.31, 95 percent CI:
1.54–44.86), and flushing (RR = 7.10, 95 percent CI: 1.58–31.95) (Figures 26–29).
Meta-analysis of trials comparing different doses of sildenafil (dose-response effect).
The dose-response efficacy/harm effect of sildenafil given at a fixed dose (10 mg, 25 mg, 50
mg, and 100 mg) was assessed in six trials. 78,85,86,93,96,137 Of these, two trials were conducted in
clinically distinct groups of participants (those with spina bifida 78 and diabetes 93 ) and therefore
were not included in the meta-analysis. Therefore, the meta-analysis exploring the dose-response
effect of sildenafil was based on three trials. 86,96,137
The following two pair-wise comparisons were made:
1) Sildenafil 25 mg versus sildenafil 50 mg
2) Sildenafil 50 mg versus sildenafil 100 mg
The efficacy and harm outcomes examined in the meta-analysis (i.e., those assessed and
reported in sufficient detail in all three trial reports) were the proportions of participants with
improved erection (GEQ–Q1) and the proportions of participants who experienced a specific allcause
adverse event (i.e., headache, flushing, or visual disturbances) (Figures 30–37).
Sildenafil 25 mg versus sildenafil 50 mg – Efficacy. Proportion of participants with improved
erection (GEQ–Q1). A statistically significant greater proportion of participants in the 50 mg
sildenafil treatment group reported improved erection (GEQ–Q1) in comparison with the 25 mg
group (RR = 1.19, 95 percent CI: 1.06–1.34) (Figure 30).
Sildenafil 25 mg versus sildenafil 50 mg - Harms. Proportion of participants with headache,
flushing, or visual disturbances.
The pooled estimates for the observed between-group (50 mg sildenafil versus 25 mg
sildenafil) differences with respect to proportions of participants experiencing all-cause
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