Mechanistic analysis and experimental verification of bicarbonate-controlled enteric coat dissolution: Potential in vivo implications. 2019

J Al-Gousous, and H Ruan, and J A Blechar, and K X Sun, and N Salehi, and P Langguth, and N M Job, and E Lipka, and R Loebenberg, and M Bermejo, and G E Amidon, and G L Amidon
College of Pharmacy, University of Michigan, 428 Church Street, Ann Arbor, MI 48109, USA. Electronic address: jalgouso@umich.edu.

Enteric coatings have shown in vivo dissolution rates that are poorly predicted by traditional in vitro tests, with the in vivo dissolution being considerably slower than in vitro. To provide a more mechanistic understanding of this, the dependence of the release properties of various enteric-coated (EC) products on bulk pH and bicarbonate molarity was investigated. It was found that, at presumably in vivo-relevant values, the bicarbonate molarity is a more significant determinant of the dissolution profile than the bulk pH. The findings also indicate that this steep relationship between the dissolution of enteric coatings and bicarbonate molarity limits those coatings' performance in vivo. This is attributed to the relatively low bicarbonate molarities in human intestinal fluids. Further, the hydration and dehydrations kinetics of carbonic acid and carbon dioxide are not sufficiently rapid to reach equilibrium in the diffusion layer surrounding a dissolving ionizable solid. This results in the effective pKa of bicarbonate in the diffusion layer being lower than that determined potentiometrically at equilibrium in the bulk surrounding fluid. These results demonstrate the importance of thoroughly investigating the intestinal bicarbonate concentrations and using bicarbonate buffers or properly designed surrogates (if possible) when evaluating enteric drug products during product development and quality control.

UI MeSH Term Description Entries
D007413 Intestinal Mucosa Lining of the INTESTINES, consisting of an inner EPITHELIUM, a middle LAMINA PROPRIA, and an outer MUSCULARIS MUCOSAE. In the SMALL INTESTINE, the mucosa is characterized by a series of folds and abundance of absorptive cells (ENTEROCYTES) with MICROVILLI. Intestinal Epithelium,Intestinal Glands,Epithelium, Intestinal,Gland, Intestinal,Glands, Intestinal,Intestinal Gland,Mucosa, Intestinal
D007421 Intestine, Small The portion of the GASTROINTESTINAL TRACT between the PYLORUS of the STOMACH and the ILEOCECAL VALVE of the LARGE INTESTINE. It is divisible into three portions: the DUODENUM, the JEJUNUM, and the ILEUM. Small Intestine,Intestines, Small,Small Intestines
D008956 Models, Chemical Theoretical representations that simulate the behavior or activity of chemical processes or phenomena; includes the use of mathematical equations, computers, and other electronic equipment. Chemical Models,Chemical Model,Model, Chemical
D002021 Buffers A chemical system that functions to control the levels of specific ions in solution. When the level of hydrogen ion in solution is controlled the system is called a pH buffer. Buffer
D002214 Capsules Hard or soft soluble containers used for the oral administration of medicine. Capsule,Microcapsule,Microcapsules
D002626 Chemistry, Pharmaceutical Chemistry dealing with the composition and preparation of agents having PHARMACOLOGIC ACTIONS or diagnostic use. Medicinal Chemistry,Chemistry, Pharmaceutic,Pharmaceutic Chemistry,Pharmaceutical Chemistry,Chemistry, Medicinal
D005079 Excipients Usually inert substances added to a prescription in order to provide suitable consistency to the dosage form. These include binders, matrix, base or diluent in pills, tablets, creams, salves, etc. Excipient,Stabilizing Agent,Stabilizing Agents,Suspending Agent,Suspending Agents,Agent, Stabilizing,Agent, Suspending,Agents, Stabilizing,Agents, Suspending
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D006863 Hydrogen-Ion Concentration The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH pH,Concentration, Hydrogen-Ion,Concentrations, Hydrogen-Ion,Hydrogen Ion Concentration,Hydrogen-Ion Concentrations
D000082 Acetaminophen Analgesic antipyretic derivative of acetanilide. It has weak anti-inflammatory properties and is used as a common analgesic, but may cause liver, blood cell, and kidney damage. Acetamidophenol,Hydroxyacetanilide,Paracetamol,APAP,Acamol,Acephen,Acetaco,Acetominophen,Algotropyl,Anacin-3,Datril,N-(4-Hydroxyphenyl)acetanilide,N-Acetyl-p-aminophenol,Panadol,Tylenol,p-Acetamidophenol,p-Hydroxyacetanilide,Anacin 3,Anacin3

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