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[4 min read] Hydrochlorothiazide use and risk for Merkel cell carcinoma
Hydrochlorothiazide has been associated with an increased risk of squamous cell carcinoma. Recently, a Danish study investigated the association between hydrochlorothiazide use and the risk of Merkel cell carcinoma and malignant adnexal skin tumours.
Hydrochlorothiazide is a diuretic medication often used to treat high blood pressure and swelling due to fluid build up. Other uses include diabetes insipidus, renal tubular acidosis, and to decrease the risk of kidney stones in those with a high calcium level in the urine.
In the study, researchers identified patients with Merkel cell carcinoma and malignant adnexal skin tumours during 2004 to 2015 and matched the cases individually to cancer-free population controls. Using conditional logistic regression, they estimated the odds ratios (ORs) and confidence intervals (CIs) associated with cumulative use of hydrochlorothiazide.
The adjusted ORs for Merkel cell carcinoma and malignant adnexal skin tumours associated with high use (≥50,000 mg) of hydrochlorothiazide was 2.3 (95% CI 1.1-4.8) and 3.6 (95% CI 1.9-7.0), respectively, which increased to 3.3 (95% CI 1.3-8.3) and 5.6 (95% CI 2.4-13.3), respectively, with highest use (≥100,000 mg).
The study found that hydrochlorothiazide use is associated with an increased risk for Merkel cell carcinoma and malignant adnexal skin tumours.
There was no increased risk for these tumours with other anti-hypertensive drugs, except there was a tendency toward an increased risk for Merkel cell carcinoma associated with the use of furosemide (OR 1.9, 95% CI 0.9-4.0).
Other studies have shown that calcium channel blockers increased the risk of non-melanoma skin cancer and β-blockers increased the risk of melanoma, but not all studies have shown an increased risk of skin cancer with thiazide diuretics. However, the evidence is increasing that thiazides increase the risk of skin cancer, and patients with an increased skin cancer risk should be advised to have alternative anti-hypertensives. The evidence is not yet strong enough to advise against taking other anti-hypertensives.