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Bioequivalence of methylphenidate immediate-release tablets using a replicated study design to characterize
M C Meyer1, A B Straughn, E J Jarvi
1Department of Pharmaceutical Sciences, College of Pharmacy, University of Tennessee, Memphis 38163, USA. mmeyer@utmem.edu
Pharmaceutical Research
|June 28, 2000
Summary
This study compared two methylphenidate tablets, finding them bioequivalent on average. However, the generic methylphenidate showed greater variability and was not individually bioequivalent to the reference product.
Area of Science:
- Pharmacokinetics
- Drug bioavailability studies
- Pharmaceutical formulation analysis
Background:
- Methylphenidate is a widely prescribed medication for ADHD.
- Assessing the bioequivalence of generic formulations is crucial for therapeutic interchange.
- Understanding intrasubject variability is key in bioavailability studies.
Purpose of the Study:
- To evaluate the relative bioavailability of two immediate-release methylphenidate tablets.
- To characterize intrasubject variability in methylphenidate absorption.
- To determine bioequivalence using both average and individual criteria.
Main Methods:
- A replicated crossover study design with 20 subjects.
- Administration of single 20 mg doses of reference and test methylphenidate tablets.
- Plasma methylphenidate levels measured over 10 hours using GC/MS.
Main Results:
- The test methylphenidate product exhibited faster in vitro dissolution and in vivo absorption.
- Average Cmax and AUC(0-infinity) differed by 11% and 9% respectively.
- Average bioequivalence was met (90% CI 80-125%), but individual bioequivalence for Cmax was not.
Conclusions:
- The tested methylphenidate tablets demonstrated average bioequivalence.
- Higher intrasubject variability and borderline high subject-by-formulation interaction were observed for the test product.
- Individual bioequivalence was not established for the test methylphenidate tablets compared to the reference.