The FDA and GlaxoSmithKline (GSK) have strengthened the warning about using the antidepressant, Paxil, during early pregnancy.
The enhanced warning is based on early results from two studies that show a higher rate of heart-related birth defects in babies born to women who took Paxil during early pregnancy than in babies of mothers in the general population or of those who took other antidepressants.
The first study prompted an updated warning by GSK in September 2004. The results of a second study have prompted a further update that includes moving Paxil to a category "D" medication (as opposed to a category "C") for use during pregnancy.
The change specifically deals with use of the drug during early pregnancy. Category "D" drugs are those that have shown risks to fetuses. In this category, however, the benefits of the therapy may still outweigh the risks. GSK will be sending a letter to doctors with the updated information.
The data from both studies indicates heart-related birth defects, though rare, are more common among women who took Paxil in early pregnancy. GSK states: "The expectation is that in the general population, the risk of cardiovascular defects is about one per 100 infants."
According to GSK, the studies show a risk of heart-related birth defects as about 2% (2% and 1.5%) for women who used Paxil in early pregnancy. The cause of this increased risk is not clear, however. In fact, GSK states; "It’s not clear whether there’s a true causal association."
Most of the heart-related birth defects reported in the studies involved holes in the walls of the chambers of the heart (atrial and ventricular septal defects). According to the FDA: "In general, these types of defects range in severity from those that are minor and may resolve without treatment to those that cause serious symptoms and may need to be repaired surgically."
The FDA also states that early results from the two studies show women who took Paxil during the first trimester of pregnancy were about 1.5 to two times as likely to have a baby with a heart defect as all other women (using other antidepressants or none at all).
The FDA does indicate, however, that "the benefits of therapy may outweigh the potential risks to the fetus."
GSK emphasised this point by stating; "In the labeling, I think there’s some important guidance for prescribers as well as patients to take note of.”
In addition, the drugmaker states: “The labeling now advises that patients who become pregnant while they’re taking [Paxil] should certainly be informed of the potential harm to the fetus.Consideration should be given to discontinuing [Paxil] or perhaps switching to another antidepressant, unless the benefit that the mother is experiencing justifies continuing treatment. For women who intend to become pregnant or are in their first trimester of pregnancy, other treatments and options should be considered first before initiating Paxil.
So these are the recommendations that GSK and the FDA support to help put this information in a useful context for physicians as well as women to make well-informed treatment decisions."
According to GSK: "These studies that are referenced in the new labeling are largely updated analyses from the data that was the justification for the change in September. We have worked very closely with the FDA on the data interpretation, and what the labeling should say, and how to most quickly and effectively get this out into the public," she says. "It was a collaborative effort."
In any event, the results of the studies are significant and all women are well-advised to heed the enhanced warnings, and to proceed with extreme caution, and only after seeking medical advice, before taking Paxil if they are pregnant.