In silico prediction of drug dissolution and absorption with variation in intestinal pH for BCS class II weak acid drugs: ibuprofen and ketoprofen

The FDA Biopharmaceutical Classification System guidance allows waivers for in vivo bioavailability and bioequivalence studies for immediate‐release solid oral dosage forms only for BCS class I. Extensions of the in vivo biowaiver for a number of drugs in BCS class III and BCS class II have been proposed, in particular, BCS class II weak acids. However, a discrepancy between the in vivo BE results and in vitro dissolution results for BCS class II acids was recently observed. The objectives of this study were to determine the oral absorption of BCS class II weak acids via simulation software and to determine if the in vitro dissolution test with various dissolution media could be sufficient for in vitro bioequivalence studies of ibuprofen and ketoprofen as models of carboxylic acid drugs. The oral absorption of these BCS class II acids from the gastrointestinal tract was predicted by GastroPlus™. Ibuprofen did not satisfy the bioequivalence criteria at lower settings of intestinal pH of 6.0. Further the experimental dissolution of ibuprofen tablets in a low concentration phosphate buffer at pH 6.0 (the average buffer capacity 2.2 mmol l ‐1 /pH) was dramatically reduced compared with the dissolution in SIF (the average buffer capacity 12.6 mmol l ‐1 /pH). Thus these predictions for the oral absorption of BCS class II acids indicate that the absorption patterns depend largely on the intestinal pH and buffer strength and must be considered carefully for a bioequivalence test. Simulation software may be a very useful tool to aid the selection of dissolution media that may be useful in setting an in vitro bioequivalence dissolution standard. Copyright © 2012 John Wiley & Sons, Ltd.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94252/1/bdd1800.pd

Regulatory aspects in modified-release drug delivery

Modified-release products are produced with the goal of delivering medicines that are efficacious, are acceptably safe and have a predictable time course of delivery. In this context, modified release refers to all types of formulations with modified release, including fast (rapid), delay, sustained release, targeted, and controlled-release formulations for the various routes of administration possible. Achieving regulatory approval is an integral part in the development and commercialization of any modified-release product. This overview chapter will emphasize conventional products, recognizing that although approaches differ somewhat between the major regulatory jurisdictions regulatory authorities will require documentation demonstrating that, in common with more standard preparations, such pharmaceutical products meet Good Manufacturing Practices (GMP); quality control specifications; and pharmaceutical product interchangeability (1). In general, such approval requires evidence that the following are well defined: n As an active drug substance in its properties, manufacture, characterization, control, choice of storage container, and stability n The drug product in terms of its formulation, manufacturing process, manufacture, excipient control, its control, choice of storage container and stability n The pharmacokinetics and biopharmaceutics and, possibly, pharmacodynamics of the drug product and/or n Demonstration of safety and efficacy by clinical trial The precise nature and form of the evidence does differ greatly between the countries providing regulatory approval. In general, two somewhat different but increasingly convergent strategies are used. The United States has very detailed process driven procedures that are applied in product approval as described in a later chapter by Marroum (2). In contrast, the European Union (EU) provides guidelines for what is seen as the norm for various delivery systems (3). Here, it is possible to depart from the guidance with justification. The Japanese (4) and Canadian (5) systems appear to have a number of aspects in common with the US system. In contrast, the Australian system is somewhat more flexible, largely following, and formally adopting, the European Medicines Agency (EMEA) guidelines (6) but utilizing other sources of guidance or adopting a case by case approach where appropriate. The World Health Organization (WHO) provides effectively an overall harmonizing system. Interestingly, EMEA, WHO, and FDA each have one formulation category referred to as Delayed Release (1). The second is referred to as Prolonged Release by EMEA and as Extended (controlled, prolonged, sustained) Release by WHO and FDA