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Higher Dose Isn't Always Effective

Review of 18 studies finds that medium doses have the strongest effects

When a child with ADHD isn’t responding well to methylphenidate (MPH, Ritalin), upping the dose isn’t necessarily the answer, according to a review of 18 studies involving 606 subjects.

The researchers classified the MPH doses as low, medium, or high. They found that a medium dose of MPH had the strongest beneficial effects on inhibitory control. But increasing the dose past the medium dose did not make the drug work more effectively.

The side effects of MPH, such as growth retardation and difficulty in gaining weight, may become more significant at an increased dose and with long-term use. The lead researcher, Karen Vertessen, MD and PhD student at the Vrije Universiteit Amsterdam, notes that “[I]nhibitory control is just one aspect of impulsivity…. Children are more vulnerable than adults in these cases, especially since they will be just beginning to receive treatment, and so many treatment variables will still need to be established. If clinicians decide to start therapy with MPH, they need to keep a close eye on the patient and objectively evaluate every dose, to make sure that the higher dose is actually having an effect.”

Vertessen adds: “Current ADHD evaluation only uses behavioral outcomes, whereas we suggest adding neurocognitive outcomes to this evaluation.” In an accompanying comment, Dr. Kertin von Plessen, of the Centre Hospitalier Universitaire Vaudois, Lausanne, agrees that adding neurocognitive tests to the evaluation may be a highly useful option, but says they “should not be a substitute for the clinical evaluation of impulsivity during any change of medication.”

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