Avanafil: New Drug in Phosphodiesterase-5 (PDE-5) Inhibitors

Abstract

Erectile dysfunction (ED) is still an essential men’s health problem because its affect the quality of life and couple relationship. In year 1999, the prevalence of ED was 37.5 % in Thai men. That prevalence number is expected to grow with important risk factors such as increasing age and cardiovascular diseases. Phosphodiesterase-5 (PDE-5) Inhibitors have been used as first-line therapy for ED. The mechanism of action of this drug class is inhibition of the enzyme PDE-5 which is an enzyme breaks down cGMP. Without destroying cGMP, the vasodilatory effect of nitric oxide (NO) is enhanced and subsequently penile erection. Avanafil is a novel second-generation PDE-5 inhibitors which may differentiate itself from other PDE-5 inhibitors with its faster onset (can taken 15-30 minutes before sexual intercourse) and not be affected when eating with high fatty food. Avanafil has been designed to be highly selective Phosphodiesterase type 5 inhibitors and low affinity with PDE-1, PDE-6, and PDE-11. It was noted that avanafil was particularly well tolerated and showed a very low incidence of adverse drug reaction that tend to be reported with PDE-5 inhibitors such as Sildenafil, Vardenafil and Tadalafil which higher affinity with other PDE isoenzyme. For example, Sildenafil and Vardenafil associated with blurred vision and cyanopsia side effect because there are high affinities with PDE-6. In addition, Tadalafil associated with myalgia and muscle pain because it is high affinity with PDE-11.