[Chronic PDE-5 inhibition in patients with erectile dysfunction: new treatment approach using once daily Tadalafil]

Erectile dysfunction (ED) is often associated with increased cardiovascular risk. There is increasing evidence suggesting that dysfunction of the vascular endothelium with reduced bioavailability of nitric oxide (NO) may be the pathogenetic link between ED and cardiovascular disease. The crucial importance of the NO-guanylatecyclase-cGMP-phosphodiesterase pathway for penile erection is mirrored by the efficacy of phosphodiesterase-5 (PDE5) inhibitors in the treatment of ED. In contrast to other currently available PDE5 inhibitors with a half-life time of about 4 h Tadalafil has a half-life time of about 17.5 h resulting in erectile responsiveness for up to 36 h after 1 single dose. Most clinical experience has been reported with on-demand use of PDE-5 inhibitors, but meanwhile several studies were able to demonstrate that Tadalafil given daily in low (2.5 and 5 mg) doses is both highly effective and well-tolerated. In three randomized, double-blind, placebo-controlled multi-center trials, various validated measures of erectile function indicated that once daily Tadalafil at doses of 2.5, 5, and 10 mg was significantly superior to placebo.In another mono-center trial, once daily Tadalafil has shown significant efficacy even after failure of on-demand treatment. In a controlled cross-over study of on-demand versus daily Tadalafil treatment, 72% of the patients preferred once daily administration, mainly because of superior and longer efficacy allowing a more spontaneous sexual life. Interestingly in a pilot study of on-demand versus chronic administration of Tadalafil for 4 weeks, only regular dosing improved several markers of endothelial function.