1.1 BACKGROUND OF STUDY
Sildenafil citrate is a potent, competitive phosphodiesterase type 5 isoenzyme inhibitor , it was the first in a class of effective oral treatment for erectile dysfunction(ED) of varying etiologies including erectile dysfunction associated with drugs, diabetes, other general medical conditions and spinal cord injury (Giulinao et al). Sildenafil citrate was initially studied for use in hypertension and angina pectoris but since it induced penile erection to patients who took the drug in clinical trials (ABM), Pfizer decided to market it for erectile dysfunction rather than Angina, and was approved for use for erectile dysfunction by the FDA on March 27th 1998. Sildenafil popularity with young adults has increased over the years (Peterson, 2001). The availability of sildenafil has changed the view of ED management, as well as increased patient access to disease management resources.(Boyce et.al 2001). A significant portion of the literature describing the use of sildenafil in recreational settings comes from Great Britain. The authors of one British review in 2000 reported that the PDE5 inhibitor was supplied via the Internet, as well as from street sources.(Downie et.al 2000) Opioid abusers were seeking the drug to improve sexual performance that might be adversely affected by long-term opiate use. Healthy menwere also seeking the drug in the belief that it would improve their sexual performance. The perceived risks of obtaining sildenafil via such online sources were assessed in 1999. Ten virtual pharmacies that sold sildenafil pursuant to an online prescription issued by an affiliated physician were assessed for their extent of dispensing the drug despite evident patient contraindications.(Eysenbach et.al1999) Investigators posed as a 69-year-old obese woman with coronary artery disease and hypertension who complained of having “no orgasm.” Concomitant medications that were listed on the patient’s request form were captopril, pravastatin, atenolol, and erythromycin. One pharmacy offered to supply cimetidine tablets to be used in conjunction with sildenafil, with the explanation that concomitant use would lead to a “56% increase in plasma sildenafil concentrations…increased effectiveness would be noted with the same dose of Viagra taken with 800 mg of cimetidine.”(Eysenbachet al 1999) Three companies provided the requested drug, one of which sent an e-mail message advising the patient to discontinue the use of her other medications when taking sildenafil. Of those that failed to ship the product, two cited importation restrictions, three unknown benefits of the drug in women, and one cardiovascular concerns. The mean purchase cost per tablet was approximately twice that of prescription sildenafil obtained from a U.S. community pharmacy.
Erectile dysfunction is defined as the inability to achieve and sustain an erection of adequate rigidity for satisfactory sexual intercourse during sexual activity of humans. Penile erection is the hydraulic effect of blood entering and being retained in sponge-like bodies within the penis. The process is most often initiated as a result of sexual arousal,when signals are transmitted from the brain to nerves in the penis. The most important organic causes are cardiovascular disease,diabetes , neurological problems(for example,trauma from prostatectomy surgery), hormonal insufficiency (hypogonadism) and the drug side effects.
Psychological impotence is where erection or penetration fails due to thoughts or feeling (psychological reasons) rather than physical impossibility;this is somewhat less frequent but can often be helped. Notably in psychological impotence there is a strong response to placebo treatment. Erectile dysfunction can have severe psychological consequences as it can be tied to relationship difficulties and masculine self-image.
Besides treating the underlying causes such as potassium deficiency or arsenic contamination of drinking water, the first line treatment of erectile dysfunction consist of a trial of PDE5 inhibitors drugs(the first of which was sildenafil ) .In some cases treatment involves prostaglandin tablets in the urethra ,injections into the penis ,a penile prosthesis ,a penis pump or vascular reconstructive surgery.