EFFECT ON DISSOLUTION FROM HALVING METHYLPHENIDATE EXTENDED-RELEASE TABLETS

OBJECTIVE: To determine the effect on in vitro dissolution from cuttin g methylphenidate extended-release tablets in half. DESIGN: Ritalin-SR (Ciba Pharmaceutical Co.) and generic methylphenidate extended-releas e (MD Pharmaceutical Inc.) tablets were dissolved in water according t o the method prescribed by the US Pharmacopeia under two conditions: w hole and halved, Samples were collected at 15, 30, and 45 minutes and at 1, 2, 3, 3.5, 4, 5, 6, and 7 hours, Methylphenidate content was det ermined by HPLC, RESULTS: Halving the tablets caused a statistically s ignificant increase in cumulative dissolution as early as 15 minutes, The difference in cumulative dissolution reached its maximum for both Ritalin-SR and generic methylphenidate extended-release tablets at 2 h ours. At this time point, the percent dissolution of the whole versus halved tablets was 57% versus 74% (Ritalin-SR), respectively, and 49% versus 67% (generic), respectively. The dissolution profiles of halved and whole extended-release methylphenidate tablets were parallel from this point through the 7-hour collection period. At 7 hours, however, there was no difference in the cumulative dissolution of halved versu s whole tablets. CONCLUSIONS: While statistical differences during in vitro dissolution do exist and pharmacokinetic ramifications have not yet been determined, the absolute differences in dissolution between h alved and whole tablets are not great. Halving methylphenidate extende d-release tablets may be a clinically acceptable means of achieving a small increment/decrement in dose without converting to a regular rele ase tablet.