Wyeth [WYE] has warned that its antidepressant Effexor (venlafaxine) is not effective for treating depression in children and teenagers, raising further concerns over the safety of prescribing antidepressants to children. However, due to the drug’s ongoing success and growth it is unlikely this latest warning will have a significant effect on Effexor’s sales.
Wyeth has issued a letter to physicians stating that its serotonin and noradrenaline reuptake inhibitor (SNRI), Effexor (venlafaxine), is not effective in treating depression among children and teenagers under 18 years. The letter follows the results of several clinical trials which showed a higher incidence in children of “hostility and suicide-related adverse events, such as suicidal ideation and self-harm”.
In one of the studies, 2% of children with major depression reported suicidal thoughts with a further 2% displaying hostility – more than double the proportion of children receiving placebo. In an additional study 1% of children with generalized anxiety disorder (GAD) showed abnormal or changed behavior versus none with placebo. However, no children in the trials committed suicide.
Although Lilly’s [LLY] Prozac (fluoxetine) is currently the only antidepressant approved for use in children, physicians frequently prescribe other antidepressants. This latest warning raises concerns over the use of antidepressants in children and follows a similar warning in June 2003 when UK regulators and the FDA urged doctors not to prescribe GSK’s [GSK.L] Paxil (paroxetine) to children because of data linking it to suicidal behavior.
Effexor is currently approved for the treatment of depression, GAD and, in the US, social anxiety disorder. Since gaining approval in 1993, it has become the fourth biggest selling antidepressant in the world, generating revenues of $2.1 billion in worldwide annual sales during 2002. This is an increase of 34% or $530 million over 2001 sales ($1.5 billion). Furthermore, Effexor is the largest selling antidepressant in the SNRI class, with the XR version among the fastest growing antidepressants in the US during 2002.
Pediatric approval would have allowed the drug an extra six months market exclusivity, but outside this, the latest warning will not affect Effexor’s rapidly growing sales.