Neuroimaging research demonstrates both pharmacokinetic and pharmacodynamic differences in the euphoric and abuse liability effects of methylphenidate and cocaine in humans.21 Agents such as cocaine that demonstrate rapid absorption and rapid turnover at CNS synaptic dopamine receptors are associated with euphoric and abuse liability effects. The same rapid changes in drug concentration can be achieved through intranasal or intravenous, rather than oral, immediate-release (IR) stimulants. Drugs such as oral methylphenidate demonstrate slower absorption and longer temporal CNS dopamine receptor binding and release properties and are associated more with therapeutic effects than with abuse liability effects.
The drug release technology of long-acting stimulants that have a beaded or osmotic release mechanism or that are covalently bonded to an amino acid that mimics the pharmacokinetic properties of IR methylphenidate or IR amphetamine given 2 or 3 times daily makes intranasal and intravenous use difficult.17 Thus, while stimulants have properties consistent with abuse liability, their clinical use in ADHD patients does not suggest widespread abuse.
Stimulants are not without some abuse risk in clinical populations. Abuse rates rise in persons with ADHD comorbid with substance use disorders and/or other disruptive behavior diagnoses, such as oppositional defiant disorder and conduct disorder.22 Coexisting bipolar disorder increases the risk of stimulant abuse. A family history of substance use disorders increases risk. In such cases, careful monitoring and follow-up are recommended.
A more pressing and prevalent issue than abuse appears to be diversion of legitimately prescribed stimulants to individuals without ADHD for purposes other than to treat ADHD or narcolepsy. The results of a meta-analysis involving more than 113,000 patients showed rates of past year nonprescribed stimulant use between 5% and 9% in adolescents and between 5% and 35% in college students.17 Risk factors for stimulant abuse and diversion are shown in Table 2.
When prescribing stimulants for adolescents or college students with ADHD, a detailed discussion of stimulant diversion, abuse, and medication misuse with the patient and his or her parents is important. Teach the patient how to store the medication safely when he is living away from home.
Diagnosis and treatment
Evaluation of the patient with ADHD takes time and should include a multi-informant, multi-method, developmental assessment of symptoms, impairment, course of illness, previous assessments and treatments, school and social functioning, and comorbid conditions.23,24 The evaluation process is essentially a time-consuming cognitive endeavor of pattern matching the patient’s symptoms and disease course with what is known about the natural history of ADHD and hypothesis testing and integrating all available data. This systematic evaluation establishes that all clinical criteria for an ADHD diagnosis are met.
Faced with severe payer and clinical time constraints, many physicians diagnose ADHD by emphasizing a present oriented, cross-sectional symptom evaluation.6,25 This type of evaluation may result in overdiagnosing ADHD, or underidentifying ADHD in children with complex and comorbid presentations. A quick cursory evaluation from a too busy physician reinforces the public’s perception that stimulant medications with abuse potential are too readily prescribed for children who do not meet full diagnostic criteria for ADHD.
Once the diagnosis of ADHD is established, treatment planning depends on symptom severity and pervasiveness of functional impairment, tempered by the wishes and concerns of the patient and his family. Treatment should be individualized for each patient. Not all children with ADHD require medication. Behavioral therapy can be helpful for many. Patients with very mild ADHD may initially receive psychosocial ther-apy and educational support without medications.
Table 3 outlines an ADHD disease management strategy based on symptom severity and impairment.
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