David is a medical doctor specializing in addiction medicine, the psycho-pharmacology of drugs, new research strategies in the management of drug abuse problems, and proper prescribing practices for physicians. He is the founder of the Haight Ashbury Free Clinics of San Francisco, a fellow and past president of the American Society of Addiction Medicine, past president of the California Society of Addiction Medicine, past medical director for the California State Department of Alcohol and Drug Programs, past medical director for the California Collaborative Center for Substance Abuse Policy Research, and a Distinguished Fellow of the American Society of Addiction Medicine. David is also an adjunct professor at the University of California, San Francisco and the founder and publisher of the Journal of Psychoactive Drugs.