Avoiding adverse effects of antiepileptic drugs
For a full list of adverse effects caused by antiepileptic drugs, refer to a drug formulary.
Serious adverse reactions to antiepileptic drugs (eg hepatic failure with sodium valproate, agranulocytosis with carbamazepine) usually occur suddenly. Blood tests before starting treatment may be useful for comparison later, but there is no evidence that routine haematological and biochemical monitoring reduces the risk of adverse reactions.
Serious skin reactions to antiepileptic drugs include Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN) and drug reaction with eosinophilia and systemic symptoms (DRESS). Pharmacogenetic studies are identifying an increasing number of genes that confer a predisposition to cutaneous drug reactions. Testing for the HLA-B*1502 allele in patients of Asian origin (other than Japanese) is advised before starting therapy with carbamazepine. Some evidence suggests an increased risk of SJS/TEN in patients with the HLA-B*1502 allele when taking phenytoin or lamotrigine, but the risk appears to be lower than when taking carbamazepine1. When selecting subsequent antiepileptic drug therapy, be aware of the potential for cross-reactivity for skin adverse effects (eg carbamazepine and phenytoin).
Monitor serum 25(OH)D (vitamin D) concentration in patients on long-term antiepileptic drug therapy, especially those taking enzyme-inducing drugs or with risk factors for osteoporosis. See advice on vitamin D deficiency and osteoporosis.
See also teratogenic and neurodevelopmental effects of antiepileptic drugs.