The US Food and Drug Administration says that it has approved the antipsychotic agent Risperdal, marketed by Johnson & Johnson company Janssen LP, as a treatment for children and adolescents suffering symptomatic irritability associated with autism.

The condition includes such behaviours as aggression, deliberate self-injury and temper tantrums, according to the agency.

Risperdal (risperidone) has been available as a short-term treatment for adult schizophrenics since 1993 and is the first agent to be cleared for use in this very specific and debilitating indication. It is a major earner for J&J, bringing in more than $3.5 billion in sales last year.

The new approval was based on two eight-week clinical trials which showed that the drug was significantly more effective than placebo in improving irritability measures than placebo. The studies enrolled 156 children with autism aged between five and 16 years.

The FDA originally reviewed the application in 2005, but isued an approvable letter asking for more data on Risperdal's use in autism.