feussner1

Diversion, Trafficking, and Abuse of Methylphenidate

Gretchen Feussner
Drug Enforcement Administration

Abstract:

Since 1990, the use of methylphenidate (Ritalin�) for the treatment of ADHD in the United States has undergone considerable growth as the number of children and adults identified with serious problems with attention, impulsivity or hyperactivity escalates. The Drug Enforcement Administration has monitored this phenomena and has expressed concern about the emerging problem with the illicit use of methylphenidate among children. Data presented herein will show that methylphenidate has a high abuse potential, that abuse may lead to severe psychological addiction and that the expanded use of methylphenidate has resulted in a growing problem with the misuse/abuse of this drug among adolescents.

Introduction:

Methylphenidate (MPH, Ritalin�) is classified as a Schedule II stimulant under the Federal Controlled Substances Act (CSA). The Drug Enforcement Administration (DEA) is the primary agency involved in enforcing the CSA and is, therefore, responsible for establishing manufacturing quotas for Schedule I and II substances, registering handlers of controlled substances and monitoring the distribution and use of these substances. The Schedule II classification requires that a drug or other substance have (l) a high potential for abuse, (2) a currently accepted medical use in treatment in the United States and show that (3) abuse may lead to severe psychological or physical dependence. Studies that address the abuse liability of a drug and data relating to the diversion of a drug from legitimate handlers combined with clinical experience of actual abuse provide critical information about the abuse potential and dependence profile for a drug. This paper will review the data that explains why MPH has been placed in this classification and provide data concerning the manufacture, distribution, diversion, trafficking and abuse of MPH.

Abuse liability Studies:

Abuse liability studies provide information relating to the probability that a drug or other substance will be abused by man and are utilized to assess the abuse potential and dependence profile of a substance. Various behavioral paradigms including drug discrimination and self-administration analyses are sensitive models of human subjective and reinforcing effects. Although a comprehensive review of these studies has been published elsewhere,1 a brief summary of these data will be provided herein.

Preclinical research shows that MPH produces strong discriminative stimulus effects and will substitute for cocaine, d-amphetamine, cathinone, GBR12909 (a dopamine uptake inhibitor) and cocaine analogues across several training doses, species, and training conditions (Table 1). Animals trained to discriminate d-amphetamine from saline show generalization to MPH,2-6 animals trained to discriminate cocaine from saline show generalization to amphetamine and MPH,7-11 and animals trained to discriminate MPH from saline show generalization to amphetamine and cocaine. 12-13 These data suggest that MPH produces psychomotor stimulant effects in animal models that are amphetamine or cocaine-like in character.

In human drug discrimination studies, MPH substitutes for d-amphetamine and cocaine and produces similar patterns of subjective effects, including increased ratings of euphoria, drug liking and decreased sedation (Table 2). The physiological, subjective and behavioral effects of MPH have been studied in narcotic abusers,14 psychiatric patients,15 and normal subjects.16-19 MPH administration produces increases in "positive" mood scores, and dose-dependently increases measures of "drug liking". Low and intermediate doses of MPH produce feelings of relaxation, well-being and contentment, whereas higher doses intensify these feelings and produce dysphoria, nervousness and anxiety. MPH also dose-dependently reduces appetite and decreases caloric intake. Similar subjective effects are seen with d-amphetamine and d-methamphetamine, suggesting that these drugs have similar mechanisms of action underlying their abuse potential.