Studies Suggest SSRI Side Effects but Do they Extend to Effexor?

San Diego, CARecent studies have suggested that SSRI side effects can affect infants, but questions remain about whether the same is true for Effexor side effects. Effexor is not an SSRI (selective serotonin reuptake inhibitor), it is an SNRI (serotonin-norepinephrine reuptake inhibitor), so although there could be a risk of Effexor birth defects similar to those found with SSRI medication, less research has been done on these risks.

One study, published online in the British Medical Journal (BMJ; 1/12/12) examined the risk of persistent pulmonary hypertension of the newborn (PPHN) when mothers used an SSRI during pregnancy. The study's authors found that the risk of PPHN was increased two times when an SSRI medication was used late in pregnancy. In a subanalysis, researchers investigated the risk of PPHN when mothers used an SNRI during late pregnancy. "Exposure to the other antidepressants with an effect on serotonin activity or norepinephrine activity also generated increased risks," researchers wrote.

Although the absolute risk was still relatively low (three per 1,000 births), that the risk doubled due to exposure late in pregnancy is still a concern. Under normal circumstances with no exposure to SSRIs, the relative risk is 1.2 births per 1,000. Researchers recommended caution when treating women late in pregnancy with SSRIs.

Serotonin-norepinephrine reuptake inhibitors are different from selective serotonin reuptake inhibitors in that they affect both serotonin and norepinephrine levels in the patient's brain. Because of this difference, it is not guaranteed that the two classes of drugs would have identical side effects. That said, researchers in this study did find an increased risk of PPHN in infants exposed to venlafaxine (the generic version of Effexor) and other drugs that affect norepinephrine levels in the brain.

Persistent pulmonary hypertension of the newborn is a serious condition in which the infant does not adjust properly to breathing outside the womb. Approximately 15 percent of infants born with the condition die from it. Lawsuits have been filed against some antidepressant makers, alleging maternal use of their drugs while pregnant resulted in infants being born with PPHN.