Tapazole Warnings

Agranulocytosis is potentially a serious side effect. Patients should be instructed to report to their physicians any symptoms of agranulocytosis eg, fever or sore throat. Leukopenia, thrombocytopenia and aplastic anemia (pancytopenia) may also occur. Tapazole should be discontinued in the presence of agranulocytosis, aplastic anemia (pancytopenia), hepatitis or exfoliative dermatitis. The patient's bone marrow function should be monitored. Due to the similar hepatic toxicity profiles of thiamazole and propylthiouracil, attention is drawn to the severe hepatic reactions which have occurred with both drugs. There have been rare reports of fulminant hepatitis, hepatic necrosis, encephalopathy and death. Symptoms suggestive of hepatic dysfunction (anorexia, pruritus, right upper quadrant pain, etc) should have a prompt evaluation of liver function. Drug treatment should be discontinued promptly in the event of clinically significant evidence of liver abnormality including hepatic transaminase values exceeding 3 times the upper limit of normal.
Thiamazole can cause fetal harm when administered to a pregnant woman. Thiamazole readily crosses the placental membranes and can induce goiter and even cretinism in the developing fetus. In addition, rare instances of congenital defects eg, aplasia cutis, as manifested by scalp defects; esophageal atresia with tracheoesophageal fistula; and choanal atresia with absent/hypoplastic nipples have occurred in infants born to mothers who received thiamazole during pregnancy. If thiamazole is used during pregnancy or if the patient becomes pregnant while taking thiamazole, the patient should be warned of the potential hazard to the fetus.
Since the previously mentioned congenital defects have been reported in offspring of patients treated with thiamazole, it may be appropriate to use other agents in pregnant women requiring treatment for hyperthyroidism. Postpartum patients receiving thiamazole should not nurse their babies.