Teva Pharmaceutical has issued a voluntary recall for combination forms of its blood pressure drug amlodipine (brand name: Norvasc) because of cancer-causing impurities discovered in the tablets.

The firm said the combinations of amlodipine, which includes amlodipine / valsartan combination tablets and amlodipine / valsartan / hydrochlorothiazide combination tablets, were manufactured by India-based Mylan. The impurity found in the active pharmaceutical ingredient valsartan is N-nitroso-diethylamine, which has been classified as a probable human carcinogen.

Teva said those who are taking the amlodipine combination treatments should continue taking their medication but suggested they reach out to the pharmacists who filled the prescription for advice or an alternative treatment. Teva said a greater health risk exists for patients if they immediately stop treatment for their blood pressure without an alternative backup.