Drug Interaction Report

According to the manufacturer, methylphenidate may inhibit the metabolism of anticonvulsants including phenobarbital, phenytoin, and primidone. There have been only isolated case reports of phenytoin intoxication during coadministration with methylphenidate and none for the other anticonvulsants. Moreover, two studies found little or no effect of methylphenidate on plasma phenytoin concentrations. Thus, available evidence does not seem to support a clinically significant drug interaction. Nevertheless, it may be appropriate to monitor the pharmacologic response to these anticonvulsants more closely whenever methylphenidate (racemic) or dexmethylphenidate (the more pharmacologically active d-enantiomer) is added to or withdrawn from therapy, and the anticonvulsant dosage adjusted as necessary.

GENERALLY AVOID: Alcohol may exacerbate the adverse central nervous system effects of psychoactive drugs, including methylphenidate.

GENERALLY AVOID: Consumption of alcohol while taking certain sustained-release formulations of methylphenidate may cause rapid release of the drug, resulting in increased systemic levels of methylphenidate. In vitro studies have been conducted using Metadate CD 60 mg and Ritalin LA 40 mg capsules, as well as Concerta 18 mg tablet. At an alcohol concentration of 40%, an increase in the release rate of methylphenidate was observed in the first hour for Metadate CD and Ritalin LA, resulting in 84% and 98% of the methylphenidate being released, respectively. In contrast, there was no increased release of methylphenidate in the first hour for Concerta. These results are considered to be representative of the other available strengths of the corresponding product.

MANAGEMENT: Patients treated with methylphenidate should be advised to avoid alcohol or medications that contain alcohol.