Eli Lilly & Co. has announced on Wednesday that the Food and Drug Administration (FDA) is withholding approval on the long-acting version of schizophrenia treatment olanzapine. Furthermore, the agency does not need additional studies. The company has now said that it's preparing a risk evaluation and mitigation strategy to be submitted in the near future.

The FDA does not publicly disclose what steps are needed to win approval of selling a medicine. U.S. regulators have delayed a final decision on whether to approve Eli Lilly & Co. long-acting form of its drug Zyprexa (olanzapine). Lilly said in May it had received favorable signals from regulators and that they expected long-acting Zyprexa to become available in the United States in the near future, as the drug is already approved in Europe.

Lilly now sells Zyprexa as a once-a-day pill, plus a short-acting injection for acute agitation. The company wants to sell the long-acting injection under the name Zyprexa Adhera. The basic form of Zyprexa had 2007 sales of $4.8 billion, but it will lose US patent protection in 2011 and faces competition from cheaper generics. Even if the long-acting formulation should have more years of patent life, analysts say it has limited sales potential because it would be largely geared to hospitalized patients.

The FDA asked for more information about the drug for the better understanding of the side effects of excessive sedation events that were noticed in about 1% of patients during clinical trials, the first time it rejected the drug. The agency wants to be sure that the benefits of the drug surpass its risks. It remains to be seen if the drug will be approved after all by the FDA.