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Question 6#

Which of these is CORRECT regarding the effects of sildenafil?

A. Is excreted unmetabolised in urine
B. Erythromycin increases plasma levels of sildenafil
C. Priapism is a common side effect
D. Discontinuation due to adverse events is higher than placebo
E. Has a half life of eighteen hours

Correct Answer is B

Comment:

Answer B

Sildenafil is extensively metabolised by cytochrome P450 3A4 and 2C9. Drugs that inhibit these isoenzymes may increase sildenafil plasma levels. Erythromycin, a CYP3A4 inhibitor, has been shown to increase plasma sildenafil concentrations by 182%. Sildenafil has a low incidence of adverse effects, and these side effects are generally transient and mild to moderate in nature. In clinical trials the most common side effects were headache (16%), flushing (10%) and dyspepsia (7%). Some patients (about 3%) also reported changes in vision, predominantly colour tinge to vision, but also increased sensitivity to light or blurred vision. No cases of priapism were reported. The discontinuation rate due to adverse events among the treated patients was not significantly different from those receiving placebo (2.5% vs. 2.3%).