PDE5A and diabetes mellitus: In 7 studies, mostly conducted among a population with already well controlled diabetes, long half-life PDE5 inhibitors (tadalafil, PF-00489791) demonstrated a statistically significant reduction in HbA1c levels compared to control with a mean difference of −0.40% (−4.9 mmol/mol, 95% confidence interval (CI) [−0.66%, −0.14%], 95% CI [−7.2 mmol/mol, −1.5 mmol/mol], p = 0.002, baseline HbA1c 7.70% [60.7 mmol/mol]) (Fig. 2a).