Weeks after being accused of illegally marketing Lexapro for children, Forest Laboratories has received approval from US regulators to sell the antidepressant to teenagers.

The company announced that the US Food and Drug Administration has approved its supplemental New Drug Application for Lexapro (escitalopram) for the acute and maintenance treatment of major depressive disorder in adolescents aged 12-17. The thumbs-up from the agency is based on a data package which included eight-week studies comparing Lexapro with placebo in adolescents and the firm’s older antidepressant Celexa (citalopram) in children and adolescents.

However, that package included two other studies; one a Lexapro trial involving patients aged 7 to 17 and the other a Celexa study in adolescents. Neither study demonstrated efficacy but Forest said the FDA concluded that “maintenance efficacy can be extrapolated from adult data along with comparisons of escitalopram pharmacokinetic parameters in adults and adolescent patients”.

Forest chief executive Harold Solomon said "we have long believed that Lexapro would be of benefit for the treatment of depression in adolescents and that is why we undertook the several studies described in the package insert”. He added that “we are enormously gratified that Lexapro will be available for depressed adolescents”.

Lexapro, which is licensed from Denmark’s Lundbeck, is only the second antidepressant to be approved for the treatment of MDD in adolescents, a medical condition that affects approximately two million youngsters in the USA. The drug is already approved to treat MDD and generalised anxiety disorder in adults.

The approval comes just a month after the US Justice Department filed a suit against Forest alleging that it improperly promoted Lexapro and Celexa for off-label paediatric use. The complaint also claimed that the company paid kickbacks to physicians, including tickets for holidays and sporting events to induce them to prescribe the drugs.

The DoJ also alleges that Forest concealed the results of a negative study of Celexa for paediatric use. It argues that “illegal promotional practices” caused thousands of “false and fraudulent claims to be submitted to federal health care programmes”.

If Forest is found guilty, the US government can recover treble damages (ie on the sums paid out by the schemes) and $5,500-$11,000 for each false claim filed. Lexapro is comfortably the company’s biggest earner and had sales for its most recent quarter of $585.4 million.