From Drugs & Therapy Perspectives [TM] 

Methylphenidate Effective in Children with ADHD but Take Care

[Drug & Ther Perspect 11(8):10-13, 1998. © 1998 Adis International  Limited]

Introduction
Methylphenidate is a CNS stimulant that is used primarily in the treatment of attention deficit 
hyperactivity disorder (ADHD). In the US, methylphenidate is the most widely used psychotropic 
medication in children. The drug is well tolerated and efficacious in the treatment of ADHD.However, 
regular monitoring of vital signs, bodyweight, height, adverse effects and treatment effectiveness is 
required. Communication between the physician, patient and family is essential in determining the 
efficacy of treatment and to maximise the safety of methylphenidate.

As comorbidity is common in patients with ADHD, polypharmacy often occurs. This increases the risk 
of adverse effects as methylphenidate is known to interact with certain drugs. Furthermore, in older 
children there are concerns about the abuse of methylphenidate in order to experience a `high'.


Comorbidity Common with ADHD

The symptoms of ADHD begin in childhood and may become apparent at home, in school or in social 
settings, resulting in academic and social impairment.[1] Approximately 3 to 5% of children are affected 
by ADHD, but data on prevalence in adolescence and adulthood are limited.[2] The disorder is much 
more prevalent in males than females.[1] There is a considerable degree of comorbidity between ADHD 
and other psychiatric disorders, most commonly conduct disorder, mood disorders or anxiety.[3]

Treatment of Choice: Methylphenidate

Methylphenidate has been consistently shown to be efficacious in improving the symptoms of ADHD, 
and is able to sustain attention and target behaviours when performing typical academic work.[4] 
Although it is unclear whether the use of methylphenidate 
leads to greater academic achievement over time, the drug is 
known to improve target behaviours in 70 to 80% of children with ADHD. A similar response to 
treatment can be expected in adolescents and adults.[5-7]  Although methylphenidate is described as the 
first choice medication for ADHD, medication is not the only treatment modality, 
and consideration of the patient's home and school environments is 
important in determining a treatment plan.[8] The combination of medication and 
psychosocial intervention is an effective approach to treatment.[8]


Tailor Dosage Regimen to Avoid Problems

During treatment some children experience a `rebound' effect where behavioural symptoms or mood 
lability worsens as the effects of the medication are wearing off.[5] This can be managed by giving a 
larger dose in the morning followed by smaller subsequent doses for the remainder of the day, or by 
using a sustained-release preparation.[8]
The most common adverse reactions associated with methylphenidate are nervousness and insomnia. 
These generally occur when therapy is initiated and may be controlled by reducing the dosage of 
methylphenidate and omitting the afternoon or evening dose.[9] Other adverse effects associated with 
methylphenidate therapy occur only occasionally or rarely (see table 1).

Excessive sedation may occur and is usually related to the dosage of methylphenidate. It is important to 
note that excessive sedation is not a desired outcome of treatment.[8]

Avoid in Patients With Psychiatric Disorders...

Serious adverse reactions with methylphenidate are rare. Methylphenidate and other 
CNS stimulants are generally considered to be contraindicated in 
patients with anxiety, agitation or psychotic disorders as CNS stimulants 
may induce a sudden precipitation of these disorders.Patients with mental retardation and children 
younger than 6 years old may be at greater risk of experiencing all 
adverse effects of methylphenidate, including irritability and 
depressed mood.[8]


...But Benefits Outweigh Risks of Tic Disorders

There have been isolated cases of methylphenidate 
causing tics or exacerbating pre-existing tics.[9] However, as the 
potential benefits of CNS stimulant therapy are considered to outweigh the risk of tics, treatment with 
methylphenidate is not considered to be contraindicated in children with ADHD and comorbid tic 
disorder.[10,11]

Monitoring Recommended

80% of children receiving methylphenidate experience appetite suppression.[5,12] Although this effect is 
usually transient,[9] routine follow-up visits should include bodyweight monitoring.[8] Furthermore, 
some authorities recommend periodic monitoring of blood count, differential white cell count and platelet 
count as part of routine follow-up.[8] This is because leucopenia and anaemia have been associated with 
methylphenidate treatment, although no direct causal relationship has been established.[8]

Overuse of Methylphenidate?

There is concern for overdiagnosis of ADHD because the medications used to treat the condition are 
CNS stimulants. However, methylphenidate is not prescribed more than would be expected for the 
known prevalence of ADHD,[13] but there is considerable regional variation in the utilisation of the 
drug.[14,15]   Underdiagnosis is also of concern: certain groups of children, because of their gender or 
ethnicity, or because of poor access to healthcare, have few or no opportunities for learning or 
behavioural problems to be identified.[16] A careful differential diagnosis is essential to selecting 
appropriate treatment.


Illicit Use of Concern

The illicit use of methylphenidate and other CNS stimulants has been reported.[8] However, a national 
survey of high school senior students [17] reported that the illicit use of methylphenidate is about 1 to 
2%, significantly lower than the use of alcohol (ethanol) and marijuana in the same 
population.[18]Methylphenidate has been used both intravenously and intranasally as a drug of abuse to 
experience a `high' and has been used for the suppression of appetite.[8] The main concern about the 
illicit use of methylphenidate is when the drug is used in combination with alcohol, cocaine and 
pentazocine.[18]

There is no evidence that physical dependence or withdrawal syndromes are associated with the clinical 
use of methylphenidate. The presence of general substance abuse disorder in children and adolescents is 
related to the comorbid diagnosis of conduct disorder, rather than methylphenidate.[8]

In the US, methylphenidate is classified as a schedule 2 controlled 
substance, indicating a high potential for abuse - this is despite the action by 
various physician, state and parent groups to have the drug deregulated.[8] The drug is classified as a 
controlled drug in the UK and, in some other countries, can be prescribed only by a specialist or when a 
special license has been granted.


Take Care with Concurrent Medication

There is concern about the concomitant use of methylphenidate and other psychotropic drugs because 
methylphenidate inhibits the metabolism of various anticonvulsants and antidepressants,[19] and there is 
a trend towards using more than one agent to treat behavioural problems in children and adolescents.[20] 
Methylphenidate also inhibits the metabolism of some anticoagulants (see table 2).


Tables

Table 1. Adverse effects associated with methylphenidate treatment which occur only occasionally or 
rarely[9]

ÄCentral and peripheral nervous system
ÄHeadache 
ÄDrowsiness 
ÄDizziness 
ÄDyskinesia 
ÄAccommodation difficulties (rare) 
ÄBlurred vision (rare) 
ÄGastrointestinal tract 
ÄAbdominal pain 
ÄNausea 
ÄVomitinga 
ÄDry mouth 
ÄCardiovascular system 
ÄTachycardia 
ÄPalpitations 
ÄArrhythmias 
ÄChanges in blood pressure b and heart rateb 
ÄAngina pectoris 
ÄSkin and/or hypersensitivity 
ÄRash 
ÄPruritus 
ÄUrticaria 
ÄFever 
ÄArthralgia 
ÄAlopecia