The agency has issued a ‘not approvable’ letter to the drugmaker, citing excessive sleepiness caused by the new injectable version of the widely used antipsychotic. The move comes after an FDA advisory panel earlier this month unanimously recommended that the new form of Zyprexa be approved for marketing, although Lilly was urged to do more to learn why a small number of patients experienced extreme sedation while taking the drug.

In its letter, the FDA said it needs more information to better understand the risk and underlying cause of excessive sedation events that have been observed in about 1 percent of patients in clinical trials, according to a Lilly statement.

However, the FDA cited a new excessive sedation event that occurred shortly before the Feb. 6 hearing. Lilly alerted the agency and the advisory committee about the existence of a possible new case on Feb. 6, noting that Lilly was investigating the details of the event including conflicting information about the time of onset, the Lilly statement goes on to say.

After collecting additional info, Lilly says it confirmed - after the advisory committee hearing - that this was a case of excessive sedation and that it began between 3 to 5 hours after injection. All previous excessive sedation events had begun within three hours of injection. As with all previous patients with excessive sedation, this patient fully recovered, the drugmaker maintains.

“We are disappointed by the FDA’s decision and we are committed to ongoing discussions to better understand the agency’s perspective regarding this recent case of excessive sedation and to define the path forward and the associated timeline,” Jennifer Stotka, vp and US president of US Regulatory Affairs.

In documents submitted to the FDA recently, Lilly argued that the unusual side effect is found in both the pill and the new injectable version. Look on page 56, where it says there were “no differences in the incidence or timing of sedation” events between old and new forms of Zyprexa. In explaining the sedation, the drugmaker suggested the side effects may have been due to docs incorrectly injecting Zyprexa directly into the bloodstream, instead of into the muscle, because absorption takes place in just a few hours instead of days or more.