The active ingredient of generic Viagra is sildenafil citrate which is a vasodilator.It increases the diameter of the arteries by dilating them. As a result of this dilatation, the blood supply to the pelvic region increases due to which the male reproductive organ gets and erection which allows coition to take place. Besides treating sexual dysfunction which is its main sphere of action, generic Viagra also has an effect on the cardiovascular functions of a man. Some of its main effects are:

• Effects on Cardiac Contractility-

cAMP-specific PDE3 inhibitors inhibit cyclic adenosine isoenzymes in vascular and cardiac muscle due to which there is an elevation in the level of ionized calcium and contractile force. Depending on the dose, these inhibitors decrease pulmonary capillary wedge pressure and vascular resistance, at the same time increasing cardiac output. They can effectively increase the long term mortality in patients who are suffering from cardiovascular disorders. Contrasting to these inhibitors, sildenafil citrate does not have the same effect for human PDE5 as compared to PDE3 as it does not increase cAMP (Cyclic adenosine monophosphate). PDE3 can cause muscle damage (cardiotoxic) which is believed to be related to increase in intracellular cAMP in the myocardium. Preclinical studies conducted on digs showed that PDE5 is absent in cardiac myocytes and sildenafil does not have a direct inotropic effect on the trabeculae muscle in dogs. But, the effects of sildenafil citrate are yet to be studied on heart failure patients.

• Effects on Blood Pressure and Heart Rate-

Recent research conducted on the effects of sildenafil citrate showed that the patients who were administered a dose of generic Viagra had a small reduction in their systolic and diastolic blood pressures. The systolic pressure reduces by 8 to 10 mg Hg and diastolic pressure comes down by 5 to 6 mm Hg. The effect of the generic Viagra was at its peak after an hour of the dose and came down to its normal level after four hours. Despite the effect on the blood pressure, there were no effects of this drug on the heart beat. This effect was not related to the dosage or the age. Healthy volunteers were able to tolerate a dose as high as 800 mg.

• Effects on Central Hemodynamics and Peripheral Vasculature

Healthy human subjects were administered with sildenafil citrate in oral (100 to 200 mg) and intravenous routes (20 to 80 mg). Even after 12 hours, there was no significant change observed. At the last stage of intravenous sildenafil infusion, there was a decrease in the level of systemic vascular resistance index with the highest plasma concentration. The main sphere of action of sildenafil is that it is a vasodilator. In the patients who had stable angina, administration of sildenafil citrate through the veins resulted in a reduction in systemic and pulmonary arterial pressure and cardiac out put by 8 %, 25 % and 7 % respectively. Through this research, scientists concluded that seildenafil citrate is an effective vasodilator which has negligible and clinically insignificant effect of decreasing the blood pressure.

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