Double-blind Evaluation of Reinforcing and Anorectic Actions of Weight Control Medications: Interaction of Pharmacological and Behavioral Treatments

Within a behavioral self-management treatment program for overweight, 59 patients were randomly assigned to receive as an adjunct either dextroamphetamine sulfate, fenfluramine hydrochloride, or placebo in a double-blind procedure. Patients self-regulated their drug intake during a four-week medication period. Two types of behavioral-pharmacological interaction were observed: (1) drug assignment influenced participation in the behavioral treatment; and (2) drug assignment influenced the extent of medication self-administration. The dextroamphetamine group was superior in terms of behavioral treatment participation, extent of eating and exercise habit change, and weight loss. Self-administration of dextroamphetamine was most well-maintained—showing it to be a reinforcer—and self-administration of fenfluramine was suppressed below placebo levels. No patient taking either drug showed excessive drug intake, and all were, in fact, conservative in drug use. These data concerning relative reinforcing efficacy within a therapeutic medication setting are discussed in relation to data from animal models used to assess relative abuse liability of these drugs.