New Paxil Labeling Warns Of Birth-Defect Risk

GlaxoSmithKline (GSK) late last month notified health care professionals that it was strengthening product label warnings advising against the use of paroxetine (Paxil, Paxil CR) by women who are pregnant.

The company cited newly analyzed data from a retrospective epidemiologic study of major congenital malformations in infants, saying that“ preliminary results suggest an increase in the risk of congenital malformations associated with the use of paroxetine as compared to other antidepressants.”

Changes in the drug's labeling are being made after consultation with the U.S. Food and Drug Administration (FDA).

Current FDA-approved labeling lists paroxetine as a pregnancy Category C drug. Category C is defined as drugs with “no adequate and well-controlled studies in humans to determine the effect on the fetus.” Current labeling reminds prescribers that paroxetine during pregnancy should be used only if the potential benefit justifies the potential risk.

Information will be added to the product label indicating that of 3,581 pregnant women exposed to paroxetine or other antidepressants during the first trimester, use of paroxetine, compared with other antidepressants, was associated with an “increased risk of overall major congenital malformations.”

Specifically, women who took paroxetine were 2.2 times more likely to give birth to an infant with a major congenital malformation and 2.08 times more likely to give birth to an infant with a cardiovascular malformation than women on other antidepressants. Of 14 infants with a major congenital malformation born to women taking paroxetine, 10 of those with cardiovascular malformations had ventricular septal defects.

The new labeling goes on to note that a separate study based on the Swedish Medical Birth Registry “evaluated 4,291 infants exposed to SSRIs in early pregnancy. This study reported no increased risk for overall major malformations in 708 infants born to women with paroxetine exposure early in pregnancy.”

In the company's “Dear Healthcare Provider” letter regarding the new labeling, GSK said that “it is important to note that because the GSK study was designed to evaluate the relative risk of congenital malformations in infants born to women exposed to antidepressants, the study did not include a comparison to infants who were not exposed to any antidepressant. Therefore, these data should be viewed within the context of the overall prevalence of congenital malformations in the general population, which is estimated in the U.S. to be approximately 3 percent for any malformation, and approximately 1 percent for cardiovascular malformations alone.”

GSK reviewed other epidemiological studies of SSRI exposure during pregnancy in its “Dear Healthcare Provider” letter, as well as several case-control studies. In addition, it cited the National Birth Defects Prevention Study of infants delivered from 1997 through 2001.

In that study, women who took any SSRI were more likely than those who were not exposed to have an infant with omphalocele.

The strongest effect was reported in that study to be with paroxetine, which accounted for 36 percent of all exposures to an SSRI. Infants born to mothers taking paroxetine during the first trimester were found to be 6.3 times more likely to have an omphalocele compared with infants born to mothers who took no SSRIs. An association was also found between SSRI exposure and infants being born with craniosynostosis.

GSK concluded, “The differences in the results from the available studies and the diversity in type of abnormalities recently reported makes it difficult to definitively conclude a causal relationship for any particular congenital abnormality with paroxetine.”

The company, in cooperation with FDA requests, is conducting additional epidemiologic studies “to more fully understand these preliminary findings.”

The FDA's MedWatch report on paroxetine and congenital abnormalities and GSK's “Dear Healthcare Provider” letter are posted at<www.fda.gov/medwatch/safety/2005/safety05.htm#Paxil2>.▪