Three Essential Medicines Classified as Carcinogenic by IARC; Experts Urge Continued Treatment with Monitoring

The International Agency for Research on Cancer (搜索)搜索该词条 (IARC), the World Health Organization查看公司主页's specialized cancer research agency, has classified three widely prescribed medicines as "carcinogenic to humans" (Group 1). The drugs — hydrochlorothiazide查看药品详情, voriconazole查看药品详情, and tacrolimus查看药品详情 — all appear on the WHO Model List of Essential Medicines and are prescribed to millions of people worldwide. The assessment, published as Volume 137 of the IARC Monographs, expands on conclusions first released in The Lancet Oncology in November 2024. The 22-member expert panel included Indian scientist G.B. Jena.

Experts emphasized that the classification represents a hazard identification and should not prompt patients to discontinue treatment without consulting their doctors. "The IARC classification is highly relevant, particularly in India," said Kabir Sardana, Director, Professor and Head of the Department of Dermatology at Atal Bihari Vajpayee Institute of Medical Sciences and Dr. Ram Manohar Lohia Hospital.

Mechanisms of Carcinogenicity

IARC found sufficient evidence that hydrochlorothiazide查看药品详情 causes squamous cell skin carcinoma (搜索)搜索该疾病 and lip cancer. Studies from Denmark and the United States documented higher rates of non-melanoma skin cancers among long-term users, attributed to phototoxicity — the drug heightens skin sensitivity to UV radiation, raising the risk of DNA damage after sun exposure.

Voriconazole查看药品详情 was similarly linked to squamous cell skin carcinoma (搜索)搜索该疾病 in transplant recipients on prolonged therapy, operating through the same phototoxic mechanism. Tacrolimus查看药品详情, by contrast, was linked to non-Hodgkin lymphoma (搜索)搜索该疾病 and post-transplant lymphoproliferative disorder (搜索)搜索该疾病, with limited evidence for leukaemia and skin carcinoma. Unlike the other two agents, tacrolimus's risk stems from immunosuppression, which weakens the body's ability to clear abnormal cells.

The IARC Monographs identify whether an agent can cause cancer under certain circumstances but do not assess real-world risk at prescribed doses.

Clinical Implications in India

In India, hydrochlorothiazide查看药品详情 serves as a common first-line hypertension therapy, voriconazole查看药品详情 is routinely used in immunocompromised patients, and tacrolimus查看药品详情 underpins post-transplant care. Sardana noted that hydrochlorothiazide has long been recognized as carrying a risk, particularly in rural areas, the Northeast, hilly and coastal regions, and among outdoor workers such as farmers who are exposed to high levels of ultraviolet radiation.

Voriconazole查看药品详情 presents an additional concern beyond its known association with skin cancer risk. Sardana observed that the drug "is frequently prescribed without labelled indications, including for fungal skin infections caused by Trichophyton indotineae." He added that "doctors welcome measures to curb such inappropriate use."

"We cannot ignore these warnings in a country where irrational prescribing, over-the-counter availability, and poor adherence to ethical prescribing and dispensing practices remain significant challenges," Sardana stated.

Recommendations for Patients and Clinicians

Doctors recommend that patients on hydrochlorothiazide查看药品详情 or voriconazole查看药品详情 should maintain sun-protection measures, including sunscreen use, limiting UV exposure, and undergoing periodic skin checks. Transplant patients on tacrolimus查看药品详情 are already routinely monitored for skin cancers and lymphoproliferative disorders.

Experts stress that patients should not stop or alter medication without medical advice, since these drugs treat serious, often life-threatening, conditions. The priority, they said, is informed prescribing and monitoring, not a shift away from treatments whose benefits remain established.