Cocaine-like effects of intravenous procaine in cocaine addicts

Pharmacological treatments that alter dopaminergic functioning have not lessened cocaine use in addicted patients. Non-dopaminergic mechanisms may therefore be important in the chronic use of cocaine. Procaine, like cocaine, is a local anesthetic, but has only 1% of cocaine's affinity for the dopamine reuptake receptor. In order to assess the subjective effects of procaine and its similarity to cocaine, we administered procaine to nine cocaine-dependent subjects. Patients 2-3 weeks abstinent were administered placebo, low dose procaine (0.46 mg/kg), and high dose procaine (1.84 mg/kg procaine) over a single 2-hour session. Patients were assessed for craving and similarity to cocaine experience and were administered the Symptom Checklist 90 Revised (SCL90R). High dose procaine was identified as similar to cocaine and induced significant cocaine craving. High dose procaine also induced significant elevations in somatization, obsessive-compulsive symptoms, phobic anxiety, interpersonal sensitivity, anxiety, positive symptoms and global severity (from the SCL90R). Our findings suggest that procaine shares subjective effects similar to cocaine, despite a much lower affinity for the dopamine reuptake receptor. Procaine may be a useful tool to explore non-dopaminergic mechanisms of cocaine's reinforcing and addictive properties.