Hypersensitivity to thiamazole, other thiourea derivatives or to any of the excipients of Thyrozol. Moderate to severe blood count disturbances (granulocytopenia). Preexisting cholestasis not caused by hyperthyroidism. Previous damage to bone marrow after treatment with thiamazole or carbimazole.
Combination therapy with thiamazole and thyroid hormones is contraindicated during pregnancy (see Use in pregnancy & lactation under Precautions).