French pharmacovigilance survey evaluating the hepatic toxicity of coumarin

Synthetic coumarin (benzopyrone) was launched in France in 1988 for the adjuvant therapy of lymphoedema of the upper limb following radiosurgical treatment of breast cancer. Further to the reporting of hepatic reactions, a national survey has been carried out. The survey dealt with 22 cases reported to the pharmacovigilance regional centres and 20 to Knoll France company (five duplicate cases) up to June 1996. Thirty-four cases corresponding to an elevation of ALT over 2N and/or alkaline phosphatase over 1.5N (criteria chosen for selection in this survey) had been taken into account. Among these cases, a causal relationship was considered likely or probable for 15 of them. Two positive rechallenges were reported. The hepatic reactions observed between 2 to 6 months of treatment in two-thirds of the cases (average dose: 90 mg/day; i.e. recommended dose) was essentially cytolytic in 85% of the cases, with jaundice in 14 cases and hyperbilirubinaemia reported in five other cases. In 23 cases (68%), the increase of ALT exceeded 10N. Of the patients 41% were hospitalized. Severe liver failure with encephalopathy justified liver transplantation once and likely led to encephalopathy and fatal evolution in two other cases. The evolution was favourable in the other cases. The drug was prescribed for other uses than the registered indication in more than 50% of these cases. No risk factors could be identified in the survey. This survey provides a strong signal for potential hepatotoxicity of coumarin (likely due to the production of a reactive metabolite in some patients exhibiting a coumarin 7-hydroxylation deficiency).