By: Angela Zimm
Feb. 4 (Bloomberg) -- GlaxoSmithKline Plc's Paxil, Eli Lilly & Co.'s Prozac and other antidepressants may cause convulsions and other withdrawal symptoms in newborns whose mothers took the drugs during pregnancy, according to a study in the Lancet medical journal.
Paxil, also known as paroxetine, was associated with two- thirds of the infant withdrawals from antidepressants known as selective serotonin reuptake inhibitors, or SSRIs, in the study by researchers from the University of La Laguna, Spain. Drawing from reports on adverse drug reactions from a database operated by the World Health Organization, the study identified 93 cases of withdrawals in babies born to mothers who took the drugs.
``Paroxetine emerged as the most likely offending party,'' said Vladislav Ruchkin and Andres Martin of the Child Study Center at Yale University, in a commentary accompanying the study. ``And while there may be plausible explanations for such a distinction, it would be unwise to assume the other SSRIs are immune to the problem.''
SSRIs are among the most commonly prescribed drugs in the U.S. with about $11 billion in U.S. sales, according to IMS Health Inc. They have come under increased scrutiny by health regulators because of reports of child suicide risk and other potential side effects. The European Medicines Agency recommended last year SSRIs not be given to children, and the U.S. Food and Drug Administration ordered that antidepressants carry the strictest warning on child-suicide risk.
In December, EU health authorities also recommended Glaxo strengthen warnings about severe withdrawal symptoms in adults when they stop taking Paxil.
The U.S. Paxil label cautions that children exposed to the drug in the womb have developed complications requiring prolonged hospitalization, respiratory support, and tube feeding. Still, the label tells doctors to weigh the potential benefits of the drug against its risk in deciding to prescribe the medicine for pregnant women.
``No causal link between the medication and the symptoms has been established,'' Glaxo spokesman Chris Hunter-Ward said.
In the study, Paxil was linked to 64 cases of infant withdrawal, followed by Prozac with 14 cases, Pfizer Inc.'s Zoloft with 9 and H. Lundbeck A/S and Forest Laboratories Inc.'s Celexa with 7. One of the patients was taking Paxil and Prozac at the same time.
``This is ringing the bell of caution, saying please be careful,'' said Emilio Sanz, professor of pharmacology at the University of La Laguna and the study's lead author, in an interview. ``Careful doesn't mean don't treat the patient, but don't use paroxetine.''
Reports of infant withdrawal syndrome first surfaced in 1999, when 12 cases associated with Paxil were reported to the WHO database, raising a ``signal'' to the organization's drug- monitoring reviewers, the study said. More than one report on an adverse drug reaction is required before a signal is generated, as well as the seriousness of the event and quality of the information.
At the time, WHO authorities published the signal in the agency's internal bulletin, which is sent to medical agencies around the world. The information, however, was not made available to the public.
Doctors wrote more than 10 million prescriptions for antidepressants last year, according to IMS Health. Sanz said he and other researchers have no idea how many pregnant women are prescribed antidepressants.
Newborn withdrawal symptoms associated with the antidepressants also included irritability, abnormal crying and tremor, the study said. The symptoms usually disappear after a day, Sanz said. The study, however, raises concerns about the long- term effects of infants exposed to antidepressants in the womb, the researchers said.
``Such studies indicate that we need a better understanding of SSRI effects on the growing brain and call for a developmental perspective on the use of psychotropic drugs in younger patients,'' Ruchkin and Martin said in the Lancet commentary.
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