Using drugs for impotence does not increase the risk of malignant melanoma, researchers concluded in JAMA (2015; doi:10.1001/jama.2015.6604). These results contradict previous research indicating such an association.

Last year, a research team from Harvard University in Boston, United States, reported that sildenafil (Viagra), a phosphodiesterase inhibitor (PDEi) drug used against impotence, increased the risk of malignant melanoma of the skin. Those results were interpreted to mean sildenafil stimulated the growth of melanoma cells.

Researchers from Umeå University in Sweden, in collaboration with researchers in Uppsala, Lund, New York, now have published their study contradicting those findings.

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“Our research shows that already collecting one single prescription of a PDEi drug, such as [sildenafil], [tadalafil], or [vardenafil], was linked with a statistically significant increased risk of melanoma; something that speaks against a biological connection,” said Pär Stattin, MD, PhD, Professor of Urology at Umeå University, who led the investigation.

The study also shows that the risk was highest for early, superficial melanoma, which is yet another aspect raising questions about a causal association between the use of PDEi and melanoma.

Furthermore, the results show that men who received prescriptions for PDEi were healthier, had higher education, and higher income than other men, which is not surprising given that these drugs are paid out of pocket in contrast to most other drugs in Sweden.

The study was 30 times larger than the American study and was conducted using data from the Swedish Prescribed Drug Register, the Swedish Melanoma Register, and other health care registers and demographic databases in Sweden.

“Our results speak against [the idea] that drugs for impotence increase the risk of melanoma. Data rather suggest that men using Viagra, Cialis, and Levitra tend to sunbathe more, are more health-conscious and more often seek medical care for skin moles; leading to a higher risk of a melanoma diagnosis. The most important risk factor for melanoma is exposure to strong sunlight, so protection against UV exposure remains the cornerstone in melanoma protection,” concluded Dr. Stattin.