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Contempo 1999 |


Mark S. Litwin, MD, MPH
JAMA. 1999;281(6):495-496. doi:10.1001/jama.281.6.495.
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For the specialty of urology, 1998 was the year of the penis. Last spring the field of urology was taken by storm with the Food and Drug Administration's (FDA's) approval of oral sildenafil citrate (Viagra) for the treatment of male erectile dysfunction. The identification of nitric oxide as a penile neurotransmitter1 paved the way for sildenafil, a selective cyclic guanosine monophosphate (GMP)–specific phosphodiesterase inhibitor that increases cyclic GMP levels, thus enhancing the effect of nitric oxide in response to sexual stimulation. In the penis, the effect of sildenafil is to increase cavernosal smooth muscle dilation, a requisite component of erection. Coincidentally, 3 US researchers—Louis J. Ignarro, Robert F. Furchgott, and Ferid Murad—were awarded the 1998 Nobel Prize for elucidating the physiology of nitric oxide, the first gas discovered to act as a human signal molecule. In their sentinel article, Goldstein et al2 described the results of a double-masked, placebo-controlled clinical trial in which sildenafil dramatically improved patient performance on the International Index of Erectile Function, a validated patient-based measure of sexual function. Adverse effects were minor and included mild headache, facial flushing, rhinitis, dyspepsia, or blue-hued vision.


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