There have been worries that Viagra and similar erectile dysfunction medications, called PDE5 inhibitors, could increase the risk of developing skin cancer. However, a recent study has found that these medications do not significantly increase the risk of melanoma, putting many men at ease about this possible side effect.

The study comes from Dr. Anthony Matthews and other researchers at the London School of Hygiene and Tropical Medicine in the United Kingdom. The researchers published their results June 14th in the journal PLOS Medicine. Previous studies on cells in the lab had suggested that PDE5 inhibitors, drugs like Viagra (sildenafil), Cialis (tadalafil), and Levitra (vardenafil), could promote the growth of skin cancer cells. Whether this is true for men taking Viagra has been unclear, since past studies have had conflicting results, so the researchers hoped to settle the matter once and for all.

For their study, the researchers analyzed anonymous patient records from across the UK, from the Clinical Research Practice Datalink, including 150,000 men with a PDE5 inhibitor prescription and 500,000 men without a prescription. The control group were of similar ages and from similar geographic locations to the men taking the PDE5 inhibitor drugs. In addition to looking at whether the men were taking Viagra or a similar drug, the researchers looked to see if the men were diagnosed later with malignant melanoma or another type of cancer or had a skin disease.

When they crunched the data, the researchers did find that the group taking a PDE5 inhibitor seemed to have a slightly higher risk of malignant melanoma than the group that were not taking that type of drug. However, the researchers did not find an increase in the risk of colorectal cancer but did find an increase in the risk of basal cell carcinoma and solar keratosis, both diseases related to sun exposure. Many with solar keratosis had received their diagnosis before starting to take PDE5 inhibitors. This seems to indicate that the slightly increased risk of melanoma in those taking drugs like Viagra had more to do with greater sun exposure than an increase in cancer risk.

The researchers did note some limitations for their study. Since it was based in the UK, they were unable to account for the wide range of ethnicities around the world, and other researchers had already established that melanoma risk can vary by ethnicity. That said, the study results seem to be in line with another study from Sweden that failed to find a strong link between taking drugs like Viagra and an increased melanoma risk.

According to the researchers, this study should help men set their minds at ease when taking drugs like Viagra, knowing that one of the side effects of Viagra is unlikely to be melanoma. However, the researchers point out that their study does reinforce the risk of sun exposure for developing skin cancer, and the importance of covering up and using sunscreen when out in the sun.

Erectile dysfunction, also called impotence, is the difficulty of a man getting and achieving an erection for sexual intercourse. Although most men might experience a problem getting an erection on occasion, it becomes a medical concern if the problem persists. Erectile dysfunction can have both physical and psychological causes, including medical conditions affecting nerves or blood vessels, high cholesterol, diabetes, injury, surgery or radiation therapy, alcohol and smoking, prescription and recreational drugs, hormones, performance anxiety, stress, depression, guilt, fear of intimacy, and more. About 90% of erectile dysfunction cases have physical causes, and doctors will usually prescribe PDE5 inhibitor drugs like Viagra to help.

An erection occurs when sexual stimulation triggers the release of nitric oxide (NO), accumulating cyclic guanosine monophosphate (cGMP) which dilates the blood vessels, letting blood flow into the penis. Normally the enzyme PDE5 breaks down the cGMP, reducing the blood dilation, but drugs like Viagra act as PDE5 inhibitors, blocking the PDE5 from breaking down the cGMP. This helps to keep the blood vessels dilated and blood flowing into the penis, helping men to get and maintain an erection. Each year, doctors write millions of prescriptions for Viagra and other PDE5 inhibitor drugs, as the cost of Viagra and similar drugs decreases to make them accessible to more men experiencing erectile dysfunction.