Cocaine dependence is among the most tenacious of the substance use disorders yet remains one of the few lacking an effective pharmacological intervention. As pharmacologic approaches directly targeting monoamine, GABAergic, and NMDA receptors have not been fruitful (2), new targets are required. A novel treatment approach is to disrupt the neural processes involved in cue-related memories (memory links between the external stimuli associated with drug use and the subjective drug effect). These engrained memories, when reactivated by cues, elicit craving and a return to drug use. Each cue re-exposure, however, requires the re- remembering (or reconsolidation) of the drug cue. Key molecular processes required for memory reconsolidation are NMDA receptor activation, the induction of nitric oxide (NO) synthesis and increased extracellular signal-regulated kinase (ERK) activity. In rodent models, blocking these processes changes the cue-related memory;the cue loses its potency to induce a return to drug self-administration. Lidocaine is an FDA approved medication that inhibits activation of NMDA receptors and suppresses production of NO and ERK. Lidocaine, like cocaine, is a local anesthetic with potent effects as a sodium-channel blocker. Unlike cocaine, lidocaine is essentially devoid of activity at monoamine re-uptake transporters and has no rewarding or addictive properties. As lidocaine suppresses the molecular processes required for drug cue reconsolidation and has relatively specific effects upon the striatal regions necessary for drug cue reconsolidation, lidocaine may offer a novel approach for interfering with memory reconsolidation. Two other Na+ channel blockers have also decrease craving and/or substance use in substance-dependent subjects. In this proof-of-concept approach for the treatment of cocaine addiction (modeled on a paradigm developed by our group to assess pharmacologic disruptors of PTSD-related trauma memories), the effect of lidocaine infusion following cue- induced craving will be assessed in treatment-seeking, cocaine-addicted outpatients. Immediately following the induction of cue-induced craving, lidocaine or saline will be administered in a double-blind, randomized design. A third arm will also assess lidocaine in the absence of cue-induced craving. One week following the infusion, cue-induced craving will be assessed. Cocaine use and craving (non cue-induced) will be monitored for four weeks. We propose that the systemic administration of lidocaine following the induction of cue-induced craving, relative to saline plus cue-induced craving or lidocaine without cue-induced craving will block the reconsolidation of cue memories. This will lead to a reduction in cue-induced craving upon repeated testing as well as subsequent cocaine use and basal craving. If our hypotheses are proven correct, these findings will 1) support a role for lidocaine n cocaine addiction treatment, 2) demonstrate the feasibility and efficacy of attenuating cue-induced memories, and 3) guide the development of a larger study with lidocaine.
Cocaine addiction induces a significant cost to persons suffering from this disorder and to society. Unlike opioid, alcohol, or nicotine dependence, there are no approved medications for the treatment of cocaine addiction. Pharmacological approaches requiring infrequent administrations and disrupting cocaine-cue memories would offer a significant advance to the treatment of cocaine addiction.