Effects of application to two different skin sites on the pharmacokinetics of transdermal methylphenidate in pediatric patients with attention-deficit/hyperactivity disorder.

OBJECTIVE

This study was conducted to quantify the rate and extent of methylphenidate (MPH) absorption from a transdermal system when applied to two different skin sites in pediatric subjects with attention-deficit/hyperactivity disorder (ADHD).

METHODS

In an open-label, single-dose, randomized, two-way crossover study, children (6-12 years) with ADHD were randomized to wear one MPH transdermal system (MTS) on the hip area or on the scapular area for 16 hours. The following week, subjects were crossed over to the opposite application site. Serial blood samples were collected after each MTS application and pharmacokinetic (PK) parameters for d,l-MPH were calculated. Worn MTS units were assayed to calculate the Apparent Dose absorbed from MTS.

RESULTS

PK analyses included 23 subjects. Hip and scapular application resulted in quantifiable levels of d,l-MPH, with approximately 31% higher bioavailability upon hip application. Logarithm transformed mean ratios for area under the curve (AUC) and C(max) indicated a lack of equivalence between the two sites.

CONCLUSION

MTS applied to both hip and scapular areas resulted in quantifiable plasma levels of d,l-MPH. Bioavailability of MPH from the same transdermal delivery system appears to differ substantially when applied to two different skin surfaces in young children but with similar overall skin effects assessments.