Link Between Viagra and Melanoma May Be Affected By Other Factors: Study

New research that examined the link between Viagra and melanoma has found a statistically significant increased risk among men who take low doses of the popular erectile dysfunction drug and similar medication, but raises questions about whether the medication is actually causing the spread of skin cancer cells. 

In a study published this month in the Journal of the National Cancer Institute, researchers from New York University indicate that they identified an 11% increased risk among men who use Viagra and similar drugs, known as PDE5a inhibitors. However, it was only among men with low doses of exposure and low-stage melanoma, suggesting that there was a lack of dose response and biological gradient, which are often key to proving that certain side effects are actually caused by the suspected drug.

Researchers conducted a meta-analysis of three case-controlled studies involving nearly 900,000 men, nearly 42,000 of whom were diagnosed with melanoma.

According to the findings, there was an 11% increased risk of melanoma for Viagra and other PDE5a users. However, the risk was only statistically significant in men with low exposure to the drugs, and the association only appeared among men with low-stage melanoma. The study also found an increased risk linked to basal cell cancer, which the researchers said could mean the results are being confounded with ultraviolet exposure.

“The lack of dose response, biological gradient, and specificity suggest against a causal relationship,” the researchers concluded. “The observed association may be due to confounding from other factors, in particular, sunlight exposure.”

Viagra (sildenafil citrate) was introduced by Pfizer in 1998, and it has become one of the most widely recognized brand-name medications on the market in the United States, used by millions of men to treat impotence and sexual dysfunction, including the inability to develop or maintain an erection.

Since its approval, Viagra has been prescribed to an estimated 35 million men, and is generally considered safe by most consumers. However, a growing number of reports have surfaced in recent years that suggest a potential link between Viagra and melanoma skin cancer.

In April 2014, a study published in the medical journal JAMA Internal Medicine found that men who took Viagra were 84% more likely to be diagnosed with melanoma than men who do not use the drug.

Since that time, Pfizer has faced a growing number of Viagra melanoma lawsuits filed by men throughout the United States, alleging that the drug maker knew or should have known about the risk associated with their blockbuster drug for years, yet failed to adequately warn consumers and the medical community. Similar cases have also been filed against the makers of Cialis.

The American Cancer Society indicates that melanoma is diagnosed in about 69,000 Americans each year and causes about 8,650 deaths annually. The skin cancer usually manifests as unusual moles or patches of skin. While it is often curable if caught early, once melanoma has spread beyond the skin and local lymph nodes, treatment is difficult and it may ultimately result in death.

Following any bellwether trials scheduled in late 2018 or 2019, if the makers of Viagra and Cialis fail to reach melanoma settlements to resolve large numbers of cases, hundreds of individuals lawsuits may be remanded to U.S. District Courts nationwide for individual trial dates.