Health Canada has completed a safety review of hydrochlorothiazide and has found that prolonged use of the drug could increase a person’s risk for non-melanoma skin cancer.

Hydrochlorothiazide is a prescription drug used to treat high blood pressure and swelling. It is known to make skin more sensitive to ultraviolet radiation and sunlight, meaning patients can get sunburned more easily.

Health Canada reviewed the best available evidence on the issue. Findings suggest an increased risk of non-melanoma skin cancer for patients who have used hydrochlorothiazide for more than three years. However, it is important to note that the studies reviewed had significant limitations. For example, there was a lack of patient data on sun exposure and severity, and duration of high blood pressure. Such data could help clarify the cause of the increased risk.

In light of these findings, Health Canada has concluded that prolonged use of hydrochlorothiazide may be associated with a risk of non-melanoma skin cancer that is at least four times the risk of not using hydrochlorothiazide.