Paxil is an antidepressant, manufactured by GlaxoSmithKline, used for the treatment of depression and other psychiatric disorders. Since its release in 1992, the warning label for Paxil has changed to reflect the risk of birth defects in children whose mothers were taking Paxil and the increase risk of suicidal behavior in children and adults.
The Food and Drug Administration (FDA) is the governmental agency that regulates prescription drugs, including Paxil. The FDA has a categorization system to inform doctors and their patients of drug risks to unborn babies when they are taken by pregnant mothers. The system runs from Category A, which is safest, to Category Z, which is deemed “do not use” and dangerous.
When Paxil was originally released in the United States, it was released as a pregnancy Category B, which means that:
Either animal-reproduction studies have not demonstrated a fetal risk but there are no controlled studies in pregnant women, or animal-reproduction studies have shown an adverse effect (other than a decrease in fertility) that was not confirmed in controlled studies in women in the first trimester (and there is no evidence of a risk in later trimesters).
Because it is nearly impossible to test a drug on women who are pregnant, most drugs are tested on animals. There were tests performed on pregnant rats before Paxil was sold in the United States, and while it did not appear that the rat pups were born deformed, a large number of the pups died before or shortly after birth. No tests were performed to determine why the baby rats had died.
In the mid 1990s, the FDA made GlaxoSmithKline (GSK) change the Paxil pregnancy categorization to Category C, which means that either studies in animals have revealed adverse effects on the fetus (teratogenic or embryocidal or other) and there are no controlled studies in women, or studies in women and animals are not available. Drugs should be given only if the potential benefit justifies the potential risk to the fetus.
This change was a result of the animal studies which were performed before Paxil was placed on the market but were re-reviewed by the FDA. No additional testing was planned by GSK. GSK declined to keep a pregnancy registry to track pregnant women who took Paxil, so there was no data on the effect of Paxil on pregnant women.
Finally, in 2005, new studies were performed on Paxil. The FDA issued a Public Health Advisory for Paxil on December 8, 2005 based on U.S. and Swedish studies, which showed that exposure to Paxil in the first trimester of pregnancy may be associated with an increased risk of heart birth defects. Other studies have shown an increased risk for other serious birth defects. As a result, the FDA also required that Paxil’s pregnancy category be changed to a Category D. Category D drugs have positive evidence of human fetal risk based on adverse reaction data from investigational or marketing experience or studies in humans, but potential benefits may warrant use of the drug in pregnant women despite potential risks.
The FDA advises health care professionals not to prescribe Paxil in women who are in the first three months of pregnancy or are planning pregnancy unless other treatment options are not appropriate.