Some common pills used to treat high blood pressure may cause an increased risk of skin cancers in people aged 66 and above, according to a new study.
The peer-reviewed research published in the Canadian Medical Association Journal (CMAJ) on Monday found that the prolonged intake of antihypertensive medications called thiazide diuretics, including hydrochlorothiazide, were associated with higher rates of non-melanoma and melanoma – the two major types of skin cancers.
Other blood pressure drugs such as angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers, calcium channel blockers and beta-blockers, did not increase this risk, research showed.
The study included 302,634 patients in Ontario who were prescribed an antihypertensive medication between 1998 and 2017.
Hydrochlorothiazide is known to make the skin more sensitive to ultraviolet radiation and sunlight, meaning patients can get sunburned more easily, according to Health Canada.
“The theory is that by making our skin cells more sensitive to the damage caused by ultraviolet radiation from the sun or a tanning bed, that medication might increase skin cancer risk,” said Dr. Aaron Drucker, study co-author and dermatologist at the Women’s College Hospital.
Patients who have a higher baseline risk of skin cancer and are concerned about the medications’ potential side effects should speak to their physician and consider other treatment alternatives, Drucker suggested.
In 2019, a safety review by Health Canada concluded that the 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.
“Patients taking hydrochlorothiazide should be advised to limit exposure to sunlight, avoid using tanning equipment, and use adequate protection (e.g., sunscreen with SPF 30 or higher, clothing, and hat) when exposed to sunlight to minimize the risk of non-melanoma skin cancer,” the agency recommended.
The study authors also advised periodic monitoring for skin cancer to reduce the risk in patients taking thiazide diuretics.
Melanoma skin cancer starts in melanocyte cells of the skin. The more common non-melanoma skin cancers start in basal and squamous cells of the skin.
Cancer, the leading cause of death in Canada, is responsible for 30 per cent of all deaths, according to the Canadian Cancer Society.
In Canada, one-in-two people will be diagnosed with cancer in their lifetime and one-in-four are expected to die from it, the CCS estimates.
Although most skin cancers do not cause death and can be treated with a simple surgery, an advanced squamous cell skin cancer or melanoma may put a patient’s life at risk, Drucker said.
Some common symptoms of skin cancer are bumps, lesions, spots and sores.