The US Food and Drug Administration and UK pharmaceutical giant GlaxoSmithKline have sent a warning letter to healthcare professionals in the USA indicating that its antidepressant Paxil (paroxetine) may increase the risk of suicidal behaviour in young adults.

The move was spurred by the findings of a new analysis of clinical trial data, which revealed that 11 patients out of 3,455 taking the drug tried to commit suicide versus just one out of 1,978 in the placebo group.

The product’s label will be updated to reflect the warning of an increased risk of suicidal behaviour, but the company has urged caution over a sudden change in treatment given that the evidence is centred on very small percentages.

Paxil is certainly not new to safety scrutiny. The agent - which is sold as Seroxat outside the USA – was recently linked to "major congenital malformations" most commonly heart defects - in infants born to women who took the drugs during the first trimester of pregnancy. And the drug has already been associated with an increased risk of suicidal behaviour other side of the pond.

Doctors in the UK were banned from prescribing Paxil and other antidepressants in the selective serotonin reuptake inhibitor class to children and adolescents, largely on the strength of the suicide data released late last year. This debate has been widened to ask whether adults are also affected.

Meanwhile, GSK suffered more bad news on the safety side when it emerged that the use of its measles, mumps and rubella vaccine Priorix has been suspended in Vietnam, pending an investigation into whether it caused the death of an infant.

According to media reports, there has as yet been no confirmation whether Priorix was administered to the child before it died, and Vietnamese authorities have temporarily suspended the use of all MMR vaccines as a precautionary measure.