The incidence of basal cell carcinoma in Spain is estimated at 253.23 (95% CI, 273.01−269.45) per 100 000 per year, and the incidence of cutaneous squamous cell carcinoma is 38.16 (95% CI, 31.72–39.97) per 100 000 per year.1 Thiazides are widely used diuretics in Spain and, according to the summary of product characteristics, are approved for arterial hypertension, diabetes insipidus, idiopathic hypercalciuria, and edema associated with heart, kidney, or liver failure.

The Spanish Agency of Medicines and Medical Devices (Agencia Española del Medicamento y Productos Sanitarios [AEMPS]) recently provided recommendations based on a report by the Pharmacovigilance Risk Assessment Committee. The report evaluated the risks of hydrochlorothiazide (the most widely used thiazide), after the publication of 2 epidemiological studies in Denmark based on data from national databases. The studies showed the association between administration of this diuretic and increased risk of nonmelanoma skin cancer.2–4 Patients exposed to hydrochlorothiazide at a cumulative dose of 50 000mg or more were at a 1.3-fold higher risk of basal cell carcinoma and a 3.9-fold higher risk of cutaneous squamous cell carcinoma than the reference population (persons not exposed or exposed to lower doses). This risk increased to 1.54-fold and 7.38-fold in patients with cumulative doses greater than 200 000mg.2–4 The findings reported are relevant, given that treatment of hypertension, which is the main indication for hydrochlorothiazide in these patients, is usually continuous and is maintained over many years, thus increasing the possibility of reaching the cumulative dose of the medication that has been associated with a greater risk.2

It has been proposed that the most likely biological mechanism for this increased risk would be the photosensitizing activity of the thiazides, which would increase the possibility of actinic damage. It is noteworthy that no increased risk of melanoma was observed.5

Based on the recommendations of the AEMPS, it seems relevant to identify patients who require treatment with hydrochlorothiazide owing to their risk of developing nonmelanoma skin cancer and thus to suggest the need for alternative options and provide information on suitable sun protection measures. Similarly, it would be important to identify and report new cases of nonmelanoma skin cancer that may be associated with the use of hydrochlorothiazide.