Effect of Colonic Absorption on the Pharmacokinetic Properties of Delayed-Release and Extended-Release Methylphenidate: In Vivo, In Vitro, and Modeling Evaluations.

Most stimulants used to treat attention-deficit/hyperactivity disorder are administered in the morning and absorbed in the upper gastrointestinal tract. DR/ER-MPH (formerly HLD200), an evening-dosed delayed-release and extended-release methylphenidate, is predicted to be absorbed in the proximal colon. The pharmacokinetic (PK) profile of DR/ER-MPH is characterized by an 8- to 10-hour delay in initial methylphenidate absorption and a subsequent gradual increase in plasma concentration, followed by a slow decline. To examine the relationship of absorption site to pharmacokinetics, the DR/ER-MPH formulation was altered to release methylphenidate in the small intestine and distal colon. The 3 formulations were administered in an open-label, 3-way, crossover study in healthy adults (N = 18). Compared with the small intestine formulation, the PK profile of the proximal colon (DR/ER-MPH) formulation exhibited a longer delay before initial methylphenidate absorption, decreased peak methylphenidate concentration, increased time to peak concentration, and decreased bioavailability; these characteristics were amplified in the distal colon formulation. Safety profiles fell within the expectations for methylphenidate products. Modeled PK profiles were similar between the small intestine formulation and a morning-dosed extended-release methylphenidate (both predicted to release methylphenidate in the upper gastrointestinal tract), providing additional evidence that the PK profile of DR/ER-MPH is shaped by colonic absorption.

Quantitation of film coating on Zantac 75 mg tablets and Epivir HBV 100 mg tablets by ICP-AES.

PURPOSE: To present a selective analytical Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) method developed and validated for the quantitation of tablet film coatings containing titanium. METHODS: Tablet samples were decomposed by either digestion or dry ashing. The amount of film tablet coating was calculated based on titanium content of the sample. RESULTS: The reported ICP-AES method was accurate, precise, sensitive and linear for determination of titanium concentrations from 2.9 to 8.6 ppm. CONCLUSION: This method provides an accurate determination of the amount of coating on a tablet and has general applicability for a variety of coating formulations containing different elements.