A California man who developed melanoma while taking Viagra has filed a lawsuit against Pfizer Inc., alleging that Viagra is the cause.

Plaintiff Amador H. says he began taking Viagra in 2007 at his doctor’s recommendation. In May 2012, while he was still taking Viagra, his dermatologist discovered a large macule on his right shoulder. After the macule was surgically excised, a biopsy confirmed it was melanoma.

Amador argues that this melanoma resulted from his use of Viagra. He says that since having the melanoma surgically removed, he has had to vigilantly monitor his skin for new lesions.

He says his skin cancer has caused him past and future medical expenses, which he claims are attributable to Pfizer’s alleged mishandling of the risk of melanoma associated with Viagra.

Viagra, also known by its generic name sildenafil, was originally FDA-approved in March 1998 as a treatment for erectile dysfunction. Since then it has become an enormous business success. Worldwide Viagra sales in 2013 topped $1.8 billion, despite Pfizer having lost its exclusive rights to sales in Europe that year.

Today Viagra makes up 45 percent of the U.S. market for erectile dysfunction medications. Pfizer reports that over 35 million men worldwide have been prescribed Viagra.

Viagra and Skin Cancer

Amador’s Viagra lawsuit says that Viagra’s effects at the cellular level may also be associated with the development or aggravation of melanoma. He says several studies have linked Viagra’s mechanism of action to cell mutation that can create melanocytes that develop into melanoma.

Amador cites a study published in the journal Cancer Cell in 2011 that concluded Viagra promoted melanoma cell invasion. Another study published in the Journal of Cell Biochemistry allegedly found that drugs using the same mechanism of action as Viagra could promote melanin synthesis, which can promote the development of melanoma.

The plaintiff also cited a study published online in JAMA Internal Medicine in April 2014 which found that recent users of Viagra had an 84 percent increased risk of invasive melanoma. Amador says that the publication of these studies put Pfizer on notice of the risk of melanoma associated with Viagra.

Amador argues that the risks associated with Pfizer far outweigh its usefulness. The risk of developing or aggravating melanoma, a potentially deadly skin cancer, make Viagra an unsuitable treatment for erectile dysfunction, a condition that is not fatal nor harmful to physical health.

Part of Amador’s argument faults Pfizer for allegedly making no effort to warn the public about any association between Viagra and melanoma. He says that Pfizer purposely “downplayed, understated and outright ignored” that risk. He accuses Pfizer of intentionally withholding information about Viagra and skin cancer from the public.

Amador’s Viagra lawsuit raises claims based on theories of defective design, failure to warn, negligence, breach of warranty, and violation of California consumer protection laws. He seeks a damage award including punitive damages against Pfizer, plus court costs and attorney’s fees.

This Viagra lawsuit is Case No. 4:15-CV-04888, pending in the U.S. District Court for the District of California.