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Anticonvulsants in head injury

Seizures after head injury are not uncommon. Seizures may cause secondary brain damage, and this has been the main rationale for the use of prophylactic anticonvulsant drug use in the management of head injury. A systematic review [1] sheds new light on the usefulness of such therapy.


Using extensive searching strategies, together with unpublished information from authors, ten randomised studies were found, predominantly involving adults. Anticonvulsants used were phenytoin, carbamazepine and phenobarbitone compared with placebo or no treatment, over periods mainly of one to two years. The studies used large numbers (all but two randomised more than 100 patients), but reporting quality was generally low.


In all there was information on 2036 randomised patients. Anticonvulsants reduced first week seizures significantly, by 70%, with a relative risk of 0.3 (95% CI 0.2 to 0.5). The NNT was 10 (95% CI 7 to 16). In controls 14% of patients had a seizure in the first week, compared with 5% of patients taking an anticonvulsant.

By contrast (Figure), late seizures (after one week) were not affected (14% of patients with control had a seizure, compared with 13% with anticonvulsant), nor were there significant differences in death or neurological disability. There seemed to be little difference in effectiveness between carbemazepine and phenytoin, though on limited trials. Skin rashes were estimated to occur in four of 100 patients.


The reduction in early seizures is useful, but there is no evidence that anticonvulsant drugs used at any time beyond one week after head injury reduce death or disability.


  1. G Schierhout, I Roberts. Prophylactic antiepileptic agents after head injury. A systematic review. Journal of Neurology, Neurosurgery and Psychiatry 1998 64:108-12.

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