Safety of the newer antiepileptic drug oxcarbazepine during pregnancy

Birth defects after prenatal exposure to antiepileptic drugs

BACKGROUND

Exposure to antiepileptic drugs (AEDs) in the first trimester of pregnancy has been associated with an increased risk of major congenital anomalies (MCAs) in offspring. Most of the studies, however, have been fraught with methodological shortcomings, and differences in ascertainment methods and classifications prevent meaningful data pooling. Individual studies lacked the statistical power to assess comparative risks associated with specific AEDs.

RECENT DEVELOPMENTS

Several larger-scale studies, including collaborative multinational registries, have been set up to compare MCA risks associated with different treatments, including newer generation AEDs. Results have largely been consistent with the notion that monotherapy with the most commonly used AEDs is associated with an increase in risk of MCAs by two to three times, and that the magnitude of risk increases in offspring exposed to polytherapy. Available evidence does not suggest that epilepsy per se is associated with a major increase in the risk of MCAs. Almost all studies have suggested that exposure to valproic acid is associated with a greater incidence of MCAs than other AEDs. Valproic acid is also the only AED for which a dose-dependency has been confirmed in several studies: the increase in risk of MCAs, compared with other AEDs, is especially evident at doses above 800-1000 mg/day. Data from the North American registry have suggested that phenobarbital may also have a higher teratogenic risk compared with AEDs other than valproic acid, but evidence remains inconclusive. Information about effects on fetuses of newer generation AEDs other than lamotrigine and oxcarbazepine is scant. Although teratogenic effects of lamotrigine and oxcarbazepine have not been established with certainty, none of the investigations to date identified any statistically significant difference in rates of MCAs between infants exposed to lamotrigine or oxcarbazepine and infants exposed to carbamazepine. In the case of lamotrigine, moreover, a positive correlation between maternal dose and rates of MCAs has been identified. WHERE NEXT?: Collaborative pregnancy registries worldwide are at work to fill remaining gaps in knowledge. Issues to be addressed include the comparative risks associated with phenobarbital, with low-dose valproic acid, with newer generation AEDs, and with specific AED combinations; the influence of potential confounders; and the interaction of AED-associated risks with other risk factors, such as genetic profiles. Large scale studies may also clarify whether individual AEDs differ in their ability to cause specific anomalies. Finally, studies are urgently needed to investigate other potential adverse effects of AED exposure, with special reference to effects on postnatal intellectual development.

Best Practice Guidelines for the Management of Women with Epilepsy

Being a woman with epilepsy is not the same as being a man with epilepsy. Epilepsy affects sexual development, menstrual cycle, aspects of contraception, fertility, and reproduction. MENSTRUAL CYCLE, EPILEPSY, AND FERTILITY: The diagnosis of epilepsy and the use of antiepileptic drugs (AEDs) present women of childbearing age with many problems; both the disease and its treatment can alter the menstrual cycle and fertility. CONTRACEPTION IN EPILEPSY: There are no contraindications to the use of nonhormonal methods of contraception in women with epilepsy (see Table 3). Nonenzyme-inducing AEDs (valproate sodium, benzodiazepines, ethosuximide, and levetiracetam) do not show any interactions with the combined oral contraceptive pill. There are interactions between the COCP and hepatic microsomal-inducing AEDs (phenytoin, barbiturates, carbamazepine, topiramate [doses above 200 mg/day], and oxcarbazepine) and also lamotrigine. SEXUALITY: The majority of women with epilepsy appear to have normal sex lives, although in some women with epilepsy, both the desire and arousal phases may be inhibited. PRECONCEPTION COUNSELING: Preconception counseling should be available to all women with epilepsy who are considering pregnancy. Women with epilepsy should be aware of a number of issues relating to future pregnancy, including methods and consequences of prenatal screening, genetics of their seizure disorder, teratogenicity of AEDs, folic acid and vitamin K supplements, labor, breast feeding, and childcare. PREGNANCY: The lowest effective dose of the most appropriate AED should be used, aiming for monotherapy where possible. Recent pregnancy databases have suggested that valproate is significantly more teratogenic than carbamazepine, and the combination of valproate sodium and lamotrigine is particularly teratogenic. Most pregnancies are uneventful in women with epilepsy, and most babies are delivered healthy with no increased risk of obstetric complications in women. BREAST FEEDING: All women with epilepsy should be encouraged to breastfeed their babies. The AED concentration profiled in breast milk follows the plasma concentration curve. The total amount of drug transferred to infants via breast milk is usually much smaller than the amount transferred via the placenta during pregnancy. However, as drug elimination mechanisms are not fully developed in early infancy, repeated administration of a drug such as lamotrigine via breast milk may lead to accumulation in the infant. THE CARE OF CHILDREN OF MOTHERS WITH EPILEPSY: Although there is much anxiety about the possible risks to a child from the mother's epilepsy, there is little published evidence. The risk of the child being harmed depends on the type of seizure and its severity and frequency, and this risk is probably small if time is taken to train mothers and caregivers in safety precautions. MENOPAUSE: During menopause, about 40% of women report worsening of their seizure disorder, 27% improve, and a third had no change. Hormone replacement therapy is significantly associated with an increase in seizure frequency during menopause, and this is more likely in women with a history of catamenial epilepsy. BONE HEALTH: Women with epilepsy are at increased risk of fractures, osteoporosis, and osteomalacia.

Abrupt Discontinuation of Psychotropic Drugs Following Confirmation of Pregnancy: A Risky Practice

A number of pregnant women suffer from psychiatric disorders that require treatment with psychotropic drugs. A literature review suggests that these medications are relatively safe to use during pregnancy. Abrupt discontinuation of these drugs can have both physiological and psychological ramifications, which include unpleasant physical symptoms and re-emergence of the psychiatric condition. Therefore, it is not good practice to discontinue these medications abruptly upon diagnosis of pregnancy.