UPDATE 1-US FDA chief to leave post when Obama takes office

(Adds background on commissioner)

WASHINGTON, Dec 16 (Reuters) - U.S. Food and Drug Administration Commissioner Andrew von Eschenbach has told staff he will leave the agency on Jan. 20, the day Barack Obama becomes president.

In a memo sent on Monday, von Eschenbach said he would return home to Texas to spend time with his family after leaving the FDA.

"Until my final farewell on January 20, I will be working together with you to prepare the FDA for the change of political leadership at the agency," von Eschenbach said in a memo to agency staff.

Von Eschenbach, a cancer surgeon, was appointed as acting commissioner by Republican George W. Bush in September 2005 and was confirmed by the Senate as permanent commissioner in December 2006.

Democrat Obama has not announced a replacement for von Eschenbach. Janet Woodcock, head of the FDA's drug center, is often mentioned as a candidate for the top job on a temporary or permanent basis. Other names mentioned as possibilities include Cleveland Clinic cardiologist Steve Nissen and Joshua Sharfstein, head of Baltimore's health department. (Reporting by Lisa Richwine; editing by Gerald E. McCormick, Dave Zimmerman)