The risk posed to unborn children by powerful epilepsy drugs could be easier to avoid, following an 11-year study. While the four most common drugs are all linked with a higher chance of birth defects, researchers believe they have pinpointed the safest.
The 3,900 patient study, published in Lancet Neurology , could help doctors work out whether to switch drugs or cut doses. The Epilepsy Society said avoiding seizures in pregnancy was a priority.
The link between epilepsy drugs and birth defects was first noticed in the 1960s, but choosing the right drug for women of childbearing age without exposing them to the risk of seizures can be a balancing act for doctors. Simply taking a patient off medication entirely is not usually an option, as uncontrolled seizures could harm both baby and mother.
Earlier studies have highlighted valproic acid as the drug most linked to birth defects, but there has been little information as to the safety of alternatives. The latest research, from the Karolinska Institute in Sweden and the University of Pavia in Italy, also looked in detail at other drugs such as carbamazepine, lamotrigine and phenobarbital. Researchers studied 3,909 women and 4,540 pregnancies. Of those, there were 230 pregnancies involving major birth defects, including heart defects and neural tube defects such as spina bifida.
None of the major drugs was given the all clear, and as the dose of each increased, so did the risk. However, the lowest risk was linked to smaller doses of lamotrigine and carbamazepine.
The researchers stressed that, regardless of which drug was used, the vast majority of women still gave birth to perfectly healthy children. They added: "Our results show that dose selection is as crucial as the choice of drug."
In an editorial in the same journal Professor W Allen Hauser, from Colombia University in New York, said that the findings were "important" because they offered alternatives to the drugs linked most strongly to problems. He said: "The data provide another reason for use of the lowest dose of a drug associated with optimum seizure control.
"Incidence of major congenital malformations associated with a low dose of a higher risk drug might be lower than that associated with a high dose of a lower-risk drug."
Professor John Duncan, Medical Director at The Epilepsy Society, said that the results would be useful to GPs with a specialist interest in epilepsy and hospital neurologists, both of whom would be well placed to offer advice to women. But he warned that controlling seizures should remain a priority, even during pregnancy: "It should be remembered that a lot of women have epilepsy, and it is not an uncommon cause of death during pregnancy.
"This research helps to clarify the extent of the risks involved with these drugs - and all drugs carry some degree of risk."