Treatment of epilepsy in women of childbearing potential - Issues in management

Epilepsy is a common disorder and approximately 20% of persons with epilepsy are of childbearing potential. The goals of treatment are to gain the best control of seizures with the least adverse effects for both mother and offspring. Diagnosing the correct epilepsy syndrome is the most important step in selecting the proper treatment, because it has been established that specific syndromes, such as juvenile myoclonic epilepsy, respond well to valproic acid (sodium valproate) and possibly lamotrigine, but not to phenytoin or carbamazepine. Conversely, valproic acid should not generally be used in women with symptomatic epilepsy because of the risk for spina bifida that is associated with the use of this drug. Anticonvulsant drugs may alter hormone levels and influence sexuality and reproduction. Anticonvulsants which induce liver metabolism decrease the effectiveness of hormone contraceptives, and their use should be modified by increasing drug doses or the frequency of administration. Pregnancy alters the pharmacokinetics of anticonvulsants by increasing their clearance or altering their binding. These effects are most prominent for phenytoin and valproic acid but may have little effect on a renally cleared, unbound anticonvulsant such as gabapentin. Both animal and human teratogenic effects have been reported for all of the standard anticonvulsants. Animal studies have shown gabapentin, tiagabine and lamotrigine to have little association with malformations, but studies in humans have thus far been limited. Pre-pregnancy evaluation and counselling are essential. The correct syndrome must be diagnosed and the appropriate anticonvulsant started before pregnancy. Folic acid supplementation should be used at all times, because some anticonvulsants deplete this vitamin. Anticonvulsant blood concentrations should be monitored, especially when toxicity is apparent or seizures occur.