Erectile dysfunction (ED) is a common problem with a prevalence of approximately 50% in men aged 40-70 years. ED is defined as the persistent inability to achieve and maintain an erection sufficient to complete sexual intercourse. Similarly Female Sexual Arousal Disorder (FSAD) affects most women. Symptoms include lack of excitement, vaginal dryness, loss of sensation and sensitivity in the genitals and nipples and low blood flow to the genitals.
Sildenafil Citrate is a selective inhibitor of phosphodiesterase type 5 (PDE5). The physiologic mechanism of penile erection involves release of nitric oxide (NO) in the corpus cavernosum during sexual stimulation. NO activates the enzyme guanylate cyclase, resulting in increased synthesis of cyclic guanosine monophosphate (cGMP) in the smooth muscle cells of corpus cavernosum. The cGMP, in turn, triggers smooth muscle relaxation, allowing increased blood flow into the penis, resulting in erection. Sildenafil Citrate enhances the effects of NO by inhibiting PDE5 that is responsible for the degradation of cGMP in the smooth muscle cells of the corpus cavernosum. Because sexual stimulation is required to initiate the local release of NO, the inhibition of PDE5 by Sildenafil Citrate has no effect in the absence of sexual stimulation.Woman using Sildenafil Citrate experiences increased warmth, lubrication and tingling in the genital area, lasting several hours and resulting in greatly increased sensitivity and a pleasurable sexual response.
Repeated oral doses of Sildenafil Citrate are required to sustain the plasma level due to its short duration of action with high liver metabolism. More importantly, the adverse effects of oral Sildenafil Citrate like headache, dyspepsia, visual disturbance and rhinitis reported in the clinical trials necessitated an alternative to the oral dosage form. Topical gel of Sildenafil Citrate is developed to overcome the above mentioned adverse effects and also sustain its effect for a longer period. Transdermal delivery of Sildenafil Citrate offers several advantages over conventional oral dosage form and the multiple dosing can be eliminated. Thus, Sildenafil Citrate1% w/w topical gel can be used as an alternative to oral Sildenafil Citrate.