Viagra and melanoma: a lifestyle issue?


Increased risk of malignant melanoma link to ED drugs likely due to greater sun exposure, researchers say

A newly published study of nearly 150,000 men prescribed sildenafil, tadalafil, or vardenafil has found a slight increase in risk of malignant melanoma compared with 560,000 controls.

The three erectile dysfunction drugs are known to inhibit the enzyme phosphodiesterase type 5 (PDE5), and reduced expression of this enzyme has been linked to increase growth of melanoma cells in vitro.

However, the researchers from the London School of Hygiene & Tropical Medicine believe the association is not causal, contradicting the findings of previous studies.

For example, a cell study published in March 2016 reportedly identified a growth-promoting pathway in melanoma cells that was enhanced by sildenafil treatment.

The authors from the University of Tübingen in Germany were confident in their conclusion that this pathway is a link between sildenafil usage and increased melanoma risk.

“Although it is not clear whether the sildenafil concentration used in our experiments is also reached in patients, the results of the pre-clinical melanoma models obtained in the present study and elsewhere combined with the recent finding of increased melanoma risk in men using sildenafil suggest that possible skin adverse effects of PDE5 inhibitors should be considered at least in patients with melanoma,” they wrote.

Results from the latest study published in PLoS Medicine tell a different story.

They show an increase in risk of cutaneous melanoma in men using PDE5 inhibitors, but also of basal cell carcinoma and solar keratosis, which are known to be related to sun exposure.

The researchers also discovered those experiencing a higher risk of solar keratosis did so even before receiving their first PDE5 prescription, suggesting they had higher rates of sun exposure on average than the control group.

“All of our observations pointed towards the small apparent increase in risk of melanoma in men prescribed PDE5 inhibitors being explained by greater sun exposure, rather than a side-effect of the drugs themselves,” says senior study author Krishnan Bhaskaran.

Another epidemiological study published in JAMA in June 2015 found that use of PDE5 inhibitors was associated with a modest but significant increased risk of malignant melanoma.

Men who filled at least one prescription for an erectile dysfunction drug faced a 21% higher risk of malignant melanoma.

However, so-called super-users – those who filled more than six prescriptions of PDE5s – did not have an elevated risk of melanoma associated with increased use.

Men who take these drugs tend of have higher disposable incomes and education levels, the authors point out, and the association may be more behaviour- and lifestyle-related than drug-related.

Previous Pharmacist loses job over anti-gay Facebook post
Next Can future zoonoses be predicted?

NOTICE: It can sometimes take awhile for comment submissions to go through, please be patient.