David A. Kessler, medical director of the Albert Einstein medical school in New York and a lecturer at Columbia University Law School, has emerged as the leading candidate for the next head of the Food and Drug Administration, sources said.

The post has been empty for almost a year following the resignation of Frank Young, who had led the agency since 1981.

Kessler's nomination has not been forwarded to the White House, but his name is apparently the only one remaining on a list of candidates prepared by an administration search committee earlier this year. Other candidates once under consideration but reportedly no longer in the running are National Commission on AIDS chairman June E. Osborn, Acting FDA Commissioner James S. Benson and California state Health Commissioner Ken Kizer.

Kessler, 39, declined to comment on the matter.

The prospect of Kessler's nomination appears to have attracted wide support inside and outside the agency, particularly on Capitol Hill, where FDA commissioners have not always enjoyed the warmest of support.

A key player in forwarding Kessler's name was Sen. Orrin G. Hatch (R-Utah), for whom Kessler served as a consultant in early 1980s, when Hatch was chairman of the Senate Committee on Labor and Human Resources, sources said.

Kessler has a reputation as a food and drug law expert, publishing extensively on the arcania of the FDA's regulatory mandate. Kessler serves on the blue-ribbon panel on the FDA set up by Health and Human Services Secretary Louis W. Sullivan, chairing the subcommittee on the drug approval process.

Kessler earned his law degree from the University of Chicago Law School in 1978 immediately after graduating from Harvard University Medical School.

If nominated, Kessler would take over the FDA at a critical point in its history. With a staff of just over 7,000 and a budget of $600 million, the agency has not recovered from the budgetary cuts of the Reagan administration. Last year, the FDA was also rocked by the worst scandal in its history, as several staff members in its generic drug division were convicted of taking gratuities.

The FDA troubles have prompted a spate of radical suggestions for reform, including separating the agency from its parent, HHS.

Earlier this week, administration officials said that Sullivan was close to chosing cardiologist Bernadine Healy as director of the National Institutes of Health. The NIH post has also been vacant for close to a year.