The US Food and Drug Administration has warned that GlaxoSmithKline’s top-selling antidepressant, Paxil (paroxetine), may be associated with birth defects.

The agency and GSK have sent out a warning to healthcare professionals indicating that Paxil and sister product Paxil CR have been linked to “major congenital malformations‚” most commonly heart defects - in infants born to women who took the drugs during the first trimester of pregnancy. The results come from a retrospective epidemiological study that suggested an increase in the risk of birth defects for paroxetine compared to other antidepressants.

GSK has already updated the precautions sections of its labelling for Paxil and Paxil CR to include the new data, but has pointed out that there was no definitive causal link between the drug and birth defects. It cites a Swedish study that found no link between the class of antidepressants that includes paroxetine and birth defects, and said it had voluntarily decided to include the data and would continue to study the issue.

However, the caution comes at a time when Paxil’s safety is already under the spotlight. The drug, which is sold as Seroxat outside the USA, has been linked to an increased risk of suicidal behaviour. Doctors in the UK have already been prohibited from prescribing Paxil and other antidepressants to children and adolescents on the strength of the suicide data [[06/12/04a]], and latterly the debate has been widened to ask whether adults are also affected [[23/08/05a]] [[22/08/05b]].

The Paxil franchise saw its sales drop 47% to £152 million in the second quarter of this year, although a portion of this decline came from a temporary suspension in the manufacturing of Paxil CR after quality control problems were uncovered at GSK’s Cidra plant in Puerto Rico [[29/07/05b]].

- Meanwhile, Sir Christopher Gent, GSK’s chairman, has identified up to four internal candidates to succeed CEO Jean-Pierre Garnier after he retires in October 2007, according to UK newspaper The Times. While he declined to name the candidates, those tipped to be in the frame include: chief operating officer David Stout; head of US operations Chris Viehbacher; Andrew Whitty, who heads up the European business; and Russell Greig, who holds the position of president, pharmaceuticals international, at the group.