Stimulant substitution in methamphetamine dependence

To the Editor

Methamphetamine, a powerful and a highly addictive central nervous system (CNS) stimulant, has gained considerable global notoriety in the past decade, with the number of methamphetamine users growing at a rate unprecedented by users of other illegal, psychoactive substances (UNODC World Drug Report, 2011). The UNODC World Drug Report describes methamphetamine abuse as a global epidemic, with emphasis on its indiscriminate use across different ages, gender, and socioeconomic groups.

The rapid CNS monoamine neurotransmitter release responsible for the highly euphorigenic and addictive nature of methamphetamine has been also shown to cause the chronic, impairing neuropsychiatric complications associated with methamphetamine addiction. Maxwell (2005), for example, has reported that extensive methamphetamine use permanently depletes striatal dopamine, resulting in well-documented high relapse rates in its users. Data on the relapse reduction potential of the medications currently employed in managing this patient population shows modest efficacy at best (Karila et al., 2010). This is because these pharmacological approaches do not take into account the need to compensate for the neuropsychiatric impairments caused by the depletion of dopamine.

A sensible, yet underexplored approach to reducing relapse in methamphetamine addiction is a properly regulated stimulant substitution program, a model similar to that employed in methadone clinics for patients with opioid dependence. At such clinics, trained addiction specialists prescribe agents such as Adderall (a combination of amphetamine and dextroamphetamine) and/or Ritalin (methylphenidate), with treatment goals of reducing the risk of relapse and abstinence maintenance. This approach has been applied on a limited basis in some European countries and at least one state in the US (Mulla and MacPherson, 2007), and clinical studies have reported significant positive results of stimulant substitution in both cocaine and methamphetamine addiction (Mulla and MacPherson, 2007; Moeller et al., 2008). Other potential benefits of stimulant substitution programs would include reduction in crime, as well as reining in the spread of HIV and other health hazards associated with the illicit use of methamphetamine.

Despite the potential advantages of this approach, there are some foreseeable problems. For example, there is an inherent risk of addiction to the prescribed substitute stimulants, similar to the data reported on methadone abuse. Another shortcoming is that stimulant substitution programs may not be financially feasible, although the social and financial cost of the growing methamphetamine abuse is unquestionably significant in itself. It is clear, however, that our current treatment of methamphetamine addiction is inadequate. An approach that would incorporate stimulant substitution may represent a viable tool in reducing the ill effects of methamphetamine abuse and dependence. Thus, the exact details of the stimulant substitution model need to be further investigated in a collaborative effort between clinicians, law enforcement agencies, and the regulatory communities.