The study was led by Anton Pottegård, associate professor of clinical pharmacology at the University of Southern Denmark in Odense, and the findings were published in the Journal of the American Association of Dermatology.
The researchers were prompted in their endeavor by the fact that HCTZ has been linked with an increased risk of lip cancer in the past. In fact, a study led by Pottegård attributed 11 percent of lip cancer cases to the drug.
Moreover, HCTZ, the authors explain, makes the skin more sensitive to the damage of ultraviolet (UV) rays, due to its photosensitizing effects. This was a further reason for the researchers to examine the drug.
HCTZ raises skin cancer risk
Using national databases, Pottegård and colleagues examined the use of HCTZ in over 80,000 patients who had been diagnosed with non-melanoma skin cancer, and compared it with its use in a group of 1.5 million healthy controls.
Additionally, the researchers considered the use of other antihypertensive medication.
The research revealed that those who took HCTZ were up to seven times more likely to develop skin cancer. More specifically, the antihypertensive drug raised the risk of both squamous cell carcinoma and basal cell carcinoma – a less serious form of skin cancer.
By contrast, none of the other antihypertensive drugs examined seemed to raise skin cancer risk.
"We knew that hydrochlorothiazide made the skin more vulnerable to damage from the sun's UV rays, but what is new and also surprising is that long-term use of this blood pressure medicine leads to such a significant increase in the risk of skin cancer," comments Pottegård.
Choosing a different drug might be advisable
Dr. Armand B. Cognetta Jr., chief division of dermatology at Florida State University in Tallahassee and a co-author on the study, weighs in on the findings, saying, "We have seen and followed many patients with different skin cancers where the only risk factor apart from exposure to sunlight seems to be hydrochlorothiazide."
"The combination of living and residing in sunny Florida while taking hydrochlorothiazide seems to be very serious and even life-threatening for some patients," he adds.
"The study carried out by Pottegård and his colleagues will have [a] great impact on skin cancer prevention and public health worldwide," Dr. Cognetta explains.
However, Pottegård cautions against dismissing the use of HCTZ altogether as a result of his study, saying, "The risk of skin cancer must, of course, be weighed against the fact that hydrochlorothiazide is an effective and otherwise safe treatment for most patients."
"Nevertheless," he continues, "our results should lead to a reconsideration of the use of hydrochlorothiazide. Hopefully, with this study, we can contribute towards ensuring safer treatment of high blood pressure in the future."
"You should not interrupt your treatment without first consulting your doctor. However, if you use hydrochlorothiazide at present, it may be a good idea to talk to your doctor to see if it is possible to choose a different medicine."