By Lisa Richwine

WASHINGTON (Reuters) - An experimental sedative from Japan's Eisai Co Ltd (4523.T: Quote, Profile, Research) appeared to be effective in a preliminary evaluation of data, U.S. drug reviewers said in an analysis released on Monday.

The Food and Drug Administration will ask an advisory panel, however, if the drug can be given safely by medical personnel without general anesthesia training, agency staff said. The panel of outside experts meets on Wednesday.

The FDA's review was ongoing but so far data seemed to back the maker's finding that the drug, Aquavan, was safe as used in clinical studies, according to the analysis dated April 11 and posted on the agency's Web site on Monday.

Eisai, Japan's fourth-largest drugmaker, is seeking FDA approval to sell Aquavan for sedation of adults undergoing various medical procedures.

The intravenous drug was tested in patients undergoing colonoscopy, as well as bronchoscopy, a procedure that gives a look at the airways, and various minor surgical procedures.

The generic sedative propofol is commonly used now for colonoscopies but requires the presence of an anesthesiologist.

Aquavan was designed to be less likely to put patients into sudden and unexpected general anesthesia and therefore permit use by more health-care workers, the FDA staff said. General anesthesia poses more risks than mild or moderate sedation.

"A preliminary review of efficacy suggests that (Aquavan) is efficacious as a sedation product," the FDA staff said.