Toward the Establishment of Standardized In Vitro Tests for Lipid-Based Formulations, Part 6: Effects of Varying Pancreatin and Calcium Levels

Abstract

Abstract. The impact of pancreatin and calcium addition on a wide array of lipid-based formulations (LBFs) during in vitro lipolysis, with regard to digestion rates and distribution of the model drug danazol, was investigated. Pancreatin primarily affected the extent of digestion, leaving drug distribution somewhat unaffected. Calcium only affected the extent of digestion slightly but had a major influence on drug distribution, with more drug precipitating at higher calcium levels. This is likely to be caused by a combination of removal of lipolysis products from solution by the formation of calcium soaps and calcium precipitating with bile acids, events known to reduce the solubilizing capacity of LBFs dispersed in biorelevant media. Further, during the digestion of hydrophilic LBFs, like IIIA-LC, the un-ionizedionized ratio of free fatty acids (FFA) remained unchanged at physiological calcium levels. This makes the titration curves at pH 6.5 representable for digestion. However, caution should be taken when interpreting lipolysis curves of lipophilic LBFs, like I-LC, at pH 6.5, at physiological levels of calcium (1.4 mM); un-ionized-ionized ratio of FFA might change during digestion, rendering the lipolysis curve at pH 6.5 non-representable for the total digestion. The ratio of un-ionized-ionized FFAs can be maintained during digestion by applying non-physiological levels of calcium, resulting in a modified drug distribution with increased drug precipitation. However, as the main objective of the in vitro digestion model is to evaluate drug distribution, which is believed to have an impact on bioavailability in vivo, a physiological level (1.4 mM) of calcium is preferred.

Toward the Establishment of Standardized In Vitro Tests for Lipid-Based Formulations, Part 4: Proposing a New Lipid Formulation Performance Classification System

“…The LFCS Consortium has the objective of developing standardized in vitro tests for LBFs that assist in identification of robust LBFs prior to preclinical and clinical evaluations. The LFCS Consortium digestion test is now used by several academic/industrial laboratories to screen out formulations that show a high risk of precipitation during dispersion or digestion. In the current paper, these concepts have been extended to determine whether modifications to the digestion test can be used to alter LBF performance and to provide for more discriminating in vitro conditions.…”

“…To this point, the work performed within the LFCS Consortium has evaluated the fate of a diverse range of eight LBFs, containing different model poorly water‐soluble drugs (PWSD), during the course of in vitro dispersion and digestion performance tests . Significant progress has been made in identifying and understanding the key experimental and formulation variables that greatly impact LBF performance.…”

Infant digestion physiology and the relevance of in vitro biochemical models to test infant formula lipid digestion

“…One of the biggest challenges in creating an in vitro model of infant digestion is finding an appropriate mimic of gastric lipase [25,[42][43][44][45][46][47]. A number of lipases (including microbial-Rhizopus oryzae and Candida antarctica lipase A, animal-rabbit gastric lipase [RGL], and recombinant sources-recombinant human gastric lipase [rHGL]) have been used to simulate gastric digestion in vitro [25,[42][43][44][45][46][47]. The question that arises is which of these lipases accurately replicates the action of human gastric lipase and can it be sourced reliably?…”

“…Several recent studies have discussed the appropriate selection of gastric lipolysis conditions, with some examining the ability of these enzymes to replicate the function of human gastric lipase using IFs as a model substrate ( Fig. 4) [25,[45][46][47]. By far the most widely used gastric lipase mimic is the microbial R. oryzae lipase (ROL) [48,49].…”

Rhamnogalacturonan-I Based Microcapsules for Targeted Drug Release

“…The pH was adjusted with a 0.2 M NaOH solution to pH 6.5. A concentrated dispersion of pancreatic extract in Milli-Q water (5 mL) was added to initiate the intestinal digestion (Pancreatic lipase activity 600 USP U mL -1 in the SIF medium) [19, 20]. In experiments without enzyme, Milli-Q water (5 mL) was added instead.…”