The absorption of the two long-acting medications used to treat symptoms of attention-deficit/hyperactivity disorder (ADHD) is differentially affected by the presence of food in the stomach, especially if that food is high in fat, according to a new study.

The data, reported in the July issue of Current Medical Research and Opinion, indicate that serum levels of methylphenidate in individuals taking the long-acting medication Concerta are not substantially different when the medication is taken with food or on an empty stomach.

In contrast, individuals in the study who took Adderall XR, an extended-release formulation of mixed amphetamine salts, displayed drastically lower early blood levels when taking the medication with food compared with taking it on an empty stomach.

The study was conducted by researchers at McNeil Consumer and Specialty Pharmaceuticals, which markets Concerta. Adderall is marketed by Shire Pharmaceuticals Group.

The study compared the effect of eating a high-fat breakfast on the absorption and distribution of a typical morning dose of each medication (36 mg of Concerta or 20 mg of Adderall) in 36 healthy adults. Breakfast consisted of eggs, buttered bread, bacon, hash-brown potatoes, and eight ounces of whole milk. Blood samples were taken 18 times over the ensuing 28-hour period. Subjects received either Concerta or Adderall following either an overnight fast or 15 minutes after eating the high-fat breakfast.

Blood levels of methylphenidate in subjects who received Concerta varied only about 3 percent between the fasting and post high-fat-meal dosings. Subjects who took Adderall after the high-fat meal, however, had on average a 55 percent decrease in their blood levels of amphetamine during the first four hours following dosing, compared with those who took Adderall after fasting.

When a drug’s absorption is significantly affected by food intake, its label usually says it is best taken either one hour before or two hours after a meal. The current approved labeling for Adderall does not address any need to take the medication on an empty stomach.

Requests by Psychiatric News for comment about the data from Shire Pharmaceuticals Group were not answered by press time. ▪