Methylphenidate is a stimulant drug that is authorised in children over six years of age as part of a comprehensive treatment programme for attention deficit hyperactivity disorder (ADHD). Treatment should be under the supervision of a specialist in childhood behavioural disorders. Its safety is closely monitored by the Medicines and Healthcare products Regulatory Agency (MHRA) in conjunction with other European regulatory authorities.
Reports of suspected adverse drug reactions (ADRs) are collected by the MHRA and Commission on Human Medicines (CHM) through the spontaneous reporting scheme, the Yellow Card Scheme. The Yellow Card Scheme provides a system for early detection of emerging drug safety hazards and routine monitoring for all medicines in clinical use.
Between January 1997 and December 2006 a total of 488 reports of suspected ADRs have been received in association with methylphenidate treatment. The reactions that were most commonly reported were recognised side effects that are listed in the product information for prescribers and patients or reactions that may be part of the underlying condition. The following table shows the number of reports received in association with methylphenidate each year between 1997 and 2006.
Year received by the MHRA Number of reports listing methylphenidate as a suspect drug 1997 22 1989 23 1999 28 2000 39 2001 50 2002 59 2003 102 2004 65 2005 90 2006 95
When interpreting spontaneous reporting data, such as the data received through the Yellow Card Scheme, there are a number of factors that need to be considered including that:
the reporting of a reaction does not necessarily mean that it is related to the drug; it may be difficult to tell the difference between something that has occurred naturally or as a result of the underlying disease rather than being caused by the medicine;
the number of reports received in association with a medicine should not be used as a basis for determining the incidence of adverse drug reactions; this is because we have limited information about how many people have taken the medicine without experiencing a reaction; and
the level of ADR reporting may fluctuate between given years due to a variety of reasons including media interest/publicity surrounding the medicine and variations in exposure to the medicine.