The MHRA issued the warning in its monthly drug safety update. The agency warns that there is a small risk of congenital cardiac defects in infants of mothers who took fluoxetine during the first trimester of pregnancy. According to the safety update, the risk is similar to that posed by paroxetine (Paxil/Seroxat).
The MHRA notes that an analysis of data from seven cohort studies found a slightly increased risk of congenital cardiac defects when fluoxetine was taken early in pregnancy. Those cardiac defects reportedly varied and ranged in severity from reversible ventricular septal defects to transposition of the great vessels. The safety update notes that the increased absolute risk is less than two per 100 pregnancies.
Prozac is an antidepressant classed as a selective serotonin reuptake inhibitor (SSRI). The MHRA says that there is not enough data to conclude that other SSRIs carry the same risk, but it is unwilling to rule out the possibility of a "class effect," meaning other drugs in the same class may carry the same risks.
The agency also says that the risk of giving birth to an infant with congenital cardiac defects should be weighed against the risks of having untreated depression during pregnancy, which carries its own risks, including low birth weight, preterm delivery and lower Apgar scores.
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The MHRA noted that it was impossible to say for certain that paroxetine was the cause of the birth defects. All it could say is that paroxetine may pose a risk to the fetus.
Among the birth defects found in the studies were ventricular septal defects (a hole in the heart), cleft lip or palate (parts of the mouth do not grow together properly) and problems with the digestive system.