Higher cumulative exposure to thiazide diuretics was associated with higher rates of keratinocyte skin cancers.

Use of certain blood pressure-lowering medications may increase risk for skin cancer, a new study shows.

Researchers reviewed data for nearly 303,000 adults in Ontario over age 65 who were prescribed medications for high blood pressure and compared their skin cancer histories with those of more than 605,000 adults who weren't taking antihypertensive drugs.

Higher cumulative exposure to thiazide diuretics was associated with higher rates of keratinocyte skin cancers, including basal cell carcinoma, squamous cell carcinoma, advanced keratinocyte carcinoma and melanoma, the study showed. 

There was no consistent evidence of association between other antihypertensive classes such as angiotensin-converting enzyme (ACE) inhibitors, beta blockers, angiotensin II receptor blockers (ARBs) and calcium channel blockers and keratinocyte carcinoma or melanoma.

“Consideration of other antihypertensive treatments in patients at high risk of skin cancer may be warranted,” the study authors conclude.

Phototoxicity induced by medication can cause cellular damage to the skin, increasing the sun's carcinogenic potential.  Health Canada, the European Medicines Agency and the US Food and Drug Administration have issued warnings regarding prolonged use of the thiazide drugs due to earlier studies linking their use to skin cancer.

The study appears in the CMAJ.