The International Agency for Research on Cancer (IARC), the WHO's cancer research agency, classified three widely used medicines as "carcinogenic to humans" (Group 1): Hydrochlorothiazide (blood pressure), Voriconazole (fungal infections) and Tacrolimus (immunosuppressant used after transplants).
The first two were linked to squamous cell skin carcinoma and Tacrolimus to non-Hodgkin lymphoma and post-transplant lymphoproliferative disorders. All three are on the WHO Model List of Essential Medicines. Experts advised patients not to stop them without medical advice, since the label identifies hazard, not risk at prescribed doses.