Sildenafil (Viagra®): A Pharmacokinetic (PK) Review

Abstract

Introduction: Erectile Dysfunction (ED) is the inability to achieve or/and maintain a sufficient penile erection for successful, satisfactory, and pleasant vaginal intercourse. National Institute of Health's division of NIDDK (National Institute of Diabetes and Digestive and Kidney Diseases) defines erectile dysfunction as a condition in which one person cannot get or keep an erection firm enough for satisfactory sexual intercourse. The usual symptoms include problems achieving a solid erection, difficulties maintaining the erected condition of the penis, and decreased sexual desire. Several factors can contribute to these penile disorders. These include neurogenic injury, endocrinological disorders, drug-affected pathology, cardiovascular disease, etc. The aim of this review was to discuss the mechanism, structure activity relation (SAR), and pharmacokinetic properties of sildenafil. Methods: A careful literature search was conducted to compile all the recent information available for sildenafil PK. Primary literature searches included PubMed, Google Scholar, Wiley online resources, etc. Results: After the completion of the lengthy process of drug discovery, sildenafil citrate was approved by the FDA to be used for erectile dysfunction in March 1998. It was the very first oral treatment for erectile dysfunction. Conclusion: Although several selective PDE 5 inhibitors are available now, sildenafil citrate is still one of the most prescribed drugs for treating penile erectile disorders.