FOCUS ON DRUG ABUSE
Methylphenidate (Vitamin R) Abuse
Pearl Isaac, B.Sc.Phm.
Recent media reports have focused on the 'overuse' and 'abuse' of methylphenidate.1-3 There have been questions of whether attention deficit hyperactivity disorder (ADHD) is being diagnosed too hastily, and perhaps inappropriately, resulting in a large increase in the number of prescriptions for this drug.4,5 Other reports describe the recreational use of methylphenidate which has been diverted from students with legitimate prescriptions.3,6
Many parents whose children are diagnosed with ADHD talk to their pharmacists about their concerns.7 Some may believe drug therapy is unnecessary, but feel pressured by their child's school.7 Others may feel that their children are stigmatized when classmates and/or teachers become aware that they are receiving methylphenidate. Pharmacists can tell parents there is no evidence that supervised appropriate treatment with methylphenidate for properly diagnosed ADHD in children leads to subsequent substance abuse.8-10
The efficacy and safety of methylphenidate therapy for the treatment of ADHD is well-documented.11,12 Drug therapy is only one component of treatment, which should also include social, behavioural and educational interventions involving parents, teachers and physicians.11,12
Parent and educator concerns about methylphenidate therapy are understandable because it is pharmacologically similar to stimulants such as cocaine and amphetamines, despite being structurally dissimilar.10 All stimulants cause the release of neurotransmitters into the synaptic cleft and inhibit their neuronal reuptake.13 Euphoria can result from an activation of mesolimbic or mesocortical dopaminergic pathways.14 Tolerance develops rapidly, leading to compulsive use and dependence in susceptible persons despite the social, legal, health and employment problems associated with its abuse.
Abuse of methylphenidate was reported sporadically in the l980s. Since then, the number of reported cases has escalated with an estimated 2.5- to six-fold increase in the number of methylphenidate prescriptions in the U.S.15 One recent television documentary estimated there had been a 45 per cent increase in prescriptions for methylphenidate in Ontario from 1993 to 1994.16
With the increase in availability, there has been a rise in illicit use. Among high school and college students, snorting of crushed methylphenidate tablets (also known as vitamin R) has recently been reported.2 Some students sell or give tablets to their friends.17 Some younger children who are receiving methylphenidate have been targeted by adolescents looking for "a high."
Parenteral abuse has been described among older individuals with long histories of polysubstance abuse.14 Methylphenidate tablets--including sustained release tablets--have been crushed and dissolved or cooked, and then used intravenously (IV).14 Often, these older users obtain access to the drug when their children are started on it. Some abusers report that physicians are often unaware of the abuse potential of methylphenidate. In the U.S., there have been reports of parents who scam physicians into prescribing methylphenidate for their 'ADHD' children.8 The prescriptions were subsequently diverted to the local street drug market.8
When snorted or injected, methylphenidate rapidly reaches the brain, resulting in effects similar to using cocaine. The main difference lies in their pharmacokinetic profile--methylphenidate's effects typically last approximately six hours,18 in contrast to 30-60 minutes for cocaine.19
Recreational abuse of methylphenidate can cause loss of appetite, anxiety, insomnia, tachycardia, hypertension, headache and psychosis. High doses can result in chest pain, tremors, seizures, paranoid delusions and formication (a sensation of bugs crawling under the skin). Stroke and myocardial infarction have sometimes resulted in a fatal outcome. After a methylphenidate binge, withdrawal symptoms such as exhaustion, lethargy and severe emotional depression have been observed.20
The health consequences of injection drug abuse are well known. On top of the usual risks (e.g., contamination, venous damage, HIV, hepatitis), there is an inordinate number of pulmonary complications in methylphenidate injection users as compared to those injecting cocaine or heroin. The water-insoluble excipients of the long-acting Ritalin preparations appear to be responsible for these pulmonary complications. The talc binder used in the tablets may cause a pulmonary inflammatory reaction that destroys elastin, leading to profound irreversible obstructive lung disease (panlobular emphysema).21 Some abusers, aware of this, try to obtain the higher dose (20 mg) sustained release preparation, believing it has a lower risk of morbidity.14
The IV abuse of the combination of crushed pentazocine and methylphenidate tablets, also known as 'poor man's cocaine' or 'Ts & Rs,' reported in western Canada and the midwestern U.S., has been reported to cause similar pulmonary disease.22,23
In spite of the risks associated with the recreational abuse of methylphenidate, the drug remains an important component of ADHD treatment. Overall, when ADHD is diagnosed and treated appropriately, the risk of problems related to methylphenidate use is minimal. Pharmacists can help support parents whose children are started on a course of methylpheniate, as well as provide information on possible abuse to educators, health care providers and addiction centres.
References available on request from Pharmacy Practice
Pearl Isaac, B.Sc.Phm., is a pharmacist at the Addiction Research Foundation, a division of the Addiction and Mental Health Services Corporation in Toronto.