Los Angeles city administrative officer Miguel Santana, who was leading efforts to close the city's $212 million budget deficit, took a leave of absence last week after being arrested for alleged drunk driving.
Santana said in a statement that he had entered an alcohol treatment program.
"I do not know how long this stage of my journey will be," he said in a statement. "I apologize to my family, friends, the mayor, City Council, CAO staff, and the entire city family for my irresponsible behavior."
Santana was arrested by the California Highway Patrol while driving home from a charity event on Friday, March 26.
Assistant CAO Raymond Ciranna, who served as interim administrative officer before Santana took the top job last year, stepped in as interim CAO again.