Alison S. Poulton, MD: Methylphenidate Dosage Necessitates Further Research

MAY 31, 2019
Laura Genn
Alison Poulton, MD, MB

Alison Poulton, MD, MB

A new meta-analysis examined past methylphenidate dosing in randomized clinical trials and cohort studies for patients with ADHD.

Investigators from the University of Sydney sought to determine maximum possible methylphenidate dosing, since efficacy increases alongside dosage. They discovered a dearth of research regarding dosage, as well as frequent deference to pharmaceutical companies’ recommendations—regardless of scientific backing or lack thereof.

In an interview with MD Magazine©, lead investigator Alison Poulton, MD, MB discussed the importance of these findings and how research on methylphenidate dosage ought to progress in the future.

MD Mag: What do you think was the most important conclusion of the meta-analysis?

Poulton: This study reveals there is no discernible evidence behind dose limits of stimulant medications used to treat children and adolescents with ADHD, which effects around 10% of children. The findings suggest current dosing guidelines are inadequate.

Dosage guidelines do not acknowledge any clinical dilemma in patients who may not be adequately treated within the specified dose range. This may mean that some patients are under-treated or that prescribing doctors may start adding in other drugs, increasing the risk of adverse effects and drug interactions.

Why is there such a lack of previous research on maximum possible methylphenidate dosage?

I think there are several reasons for the lack of research published on using stimulants at higher doses. The currently approved dose range reflects the dose range chosen by the pharmaceutical industry when carrying out the initial drug trials.

Drug trials are expensive, and the chosen dose range works well for most patients. It may not make economic sense for the industry to fund studies testing higher doses that could be associated with greater risk.

It is possible that individual doctors may have experience of using higher doses in a small number of patients, but they may be reluctant to admit to ‘off label’ prescribing. Furthermore, it can be difficult to get a small case series published as medical journals often favor large, multicenter, prospective, randomized studies.

Such studies require funding and any sponsor is likely to insist on remaining within the approved dose range, due to the medico-legal risk associated with ‘off label’ prescribing. And so the cycle continues.

What should the next step be in methylphenidate dosage research?

After a drug has been tested and is freely available, collective experience accumulates. Doctors have a duty to respond to the needs of their patients and to do their best to find the most effective treatment.

Therefore, they may try using a drug for people who are older or younger than those who participated in the drug trials, or in people who have more complex mental health. They may also try using a wider dose range.  I believe that there is experience within the community of using stimulants at higher doses. Physicians should be encouraged to collaborate within their professional associations and publish their combined experience.

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