A negative food effect, i.e. a decrease in bioavailability upon the co-administration of compounds together with food, has been attributed particularly with high solubility/low permeability compounds (BCS class III). Different mechanisms have been proposed including intestinal dilution leading to a lower concentration gradient across the intestinal wall as well as binding of the active pharmaceutical ingredient to food components in the intestine and thereby decreasing the fraction of the dose available for absorption. These mechanisms refer primarily to the compound and not to the dosage form. An increase in viscosity of the dissolution fluid will in particular affect the absorption of BCS type III compounds with preferential absorption in the upper small intestine if the API release is delayed from the dosage form. The present study demonstrated that the increase in viscosity of the dissolution medium, following ingestion of a solid meal, may drastically reduce disintegration and dissolution. For that purpose the viscosity of the standard FDA meal was determined and simulated by solutions of HPMC in buffer. As model formulations, three commercially available tablets containing trospium chloride, a BCS class III m-cholinoreceptor antagonist was used. Trospium chloride drug products have been described to undergo a negative food effect of more than 80% following ingestion with food. The tablets showed prolonged disintegration times and reduced dissolution rates in viscous media, which could be attributed to changes in the liquid penetration rates. The effect was particularly significant for film-coated tablets relative to uncoated dosage forms. The results show the necessity of considering media viscosity when designing in vitro models of drug release for BCS type III drug formulations.

Background Food-drug interactions can produce undesirable outcomes during the therapy process. The pharmacist is responsible for providing patients counseling about common food-drug interactions. Knowledge of such interactions is important to avoid their occurrence. Objective This study aimed to assess the knowledge and awareness of community pharmacists about common food-drug interactions. Setting Pharmacists working in community pharmacies across Northern Palestine. Method This is a cross-sectional study, which involved a convenience sample of 259 pharmacists working in community pharmacies in Palestine. A self-administered questionnaire consisted of 29 questions (mainly yes/no questions) was used to assess pharmacists' knowledge towards the most common and clinically significant interactions between food and medicines. Main outcome measure Pharmacists' issues related to the knowledge of food drug interactions were evaluated. Results A total of 320 questionnaires were distributed of which 259 were completed providing a response rate 80.9%. One pharmacist from each community pharmacy was asked to complete the questionnaire. The overall knowledge score of food-drug interactions for the pharmacists was 17.9 (61.7%) out of a possible maximum of 29. The pharmacists surveyed in this study have demonstrated good knowledge of some interactions; but poor knowledge of others. Conclusion Pharmacists' knowledge about common food-drug interactions is inadequate. These findings support the need for training and educational courses for pharmacists regarding food-drug interactions.

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Much interest has been expressed in this work on the role of water diffusivity in the release media as a new parameter for predicting drug release. NMR was used to measure water diffusivity in different media varying in their osmolality and viscosity. Water self-diffusion coefficients in sucrose, sodium chloride, and polymeric hydroxypropyl methylcellulose (HPMC) solutions were correlated with water uptake, disintegration, and drug release rates from trospium chloride immediate release tablets. The water diffusivity in sucrose solutions was significantly reduced compared to polymeric HPMC and molecular sodium chloride solutions. Water diffusivity was found to be a function of sucrose concentration in the media. Dosage form disintegration and drug release was to be affected by water diffusivity in these systems. This observation can be explained by hydrogen bonding formation between sugar molecules, an effect which was not expressed in sodium chloride solutions of equal osmolality. Water diffusivity and not media osmolality in general need to be considered to predict the effect of disintegration and dissolution media on drug release. Understanding the relevance of water diffusivity for disintegration and dissolution will lead to better parametrization of dosage form behavior in gastrointestinal (GI) aqueous and semisolid media.