Sildenafil for Diabetic Men With Erectile Dysfunction

To the Editor: Sildenafil is being used extensively for erectile dysfunction (ED) of all causes, due to its inhibitory effect on cyclic guanosine monophosphate (GMP) phosphodiesterase in the corpus cavernosum of the penis.¹ Most patients with diabetes have ED due to either vascular abnormalities or neuropathy. Impaired nitric oxide synthesis may be an important factor in these patients and, therefore, conservation of cyclic GMP by sildenafil is an effective mechanism to enhance nitric oxide bioavailability and thereby improve erections. Dr Rendell and colleagues² do not explain their finding that men with diabetes had a lower response rate to sildenafil than that previously reported in mixed, largely nondiabetic populations. Diabetic men may have sex hormone abnormalities that could interfere with their response to sildenafil, but Rendell et al did not report the sex hormone levels in their patients.