Mechanistic Understanding of Food Effects: Water Diffusivity in Gastrointestinal Tract Is an Important Parameter for the Prediction of Disintegration of Solid Oral Dosage Forms

Orally self-disintegrating milk protein puffs enriched with food by-products for the elderly

Supercritical fluid extrusion (SCFX) processing was used to develop milk protein-based orally self-disintegrating puffs enriched with fruit and dairy by-products, designed specifically to cater to the needs of elderly population having swallowing issues and lactose intolerance. Lactose hydrolyzed skim milk powder (LHSMP) was also added in the formulation to mitigate lactose intolerance while LHSMP was also exploited as a precursor for the polymerization of galactose and lactose to generate galacto-oligosaccharides (GOS) in the puffs. This study for the first time took advantage of the unique features of SCFX processing for in-process GOS formation and enrichment of puffs, achieving GOS contents up to 0.48 g/30 g serving of puffs, thereby making them nutritionally superior and functionally attractive snacks. The estimated nutritional profile revealed that SCFX puffs contained higher levels of protein (16.3 g/30 g), fiber (1.6 g/30 g), phenolics and other valuable nutrients compared to the starch-rich, disintegrating Market Baby puffs.

Effect of Food Viscosity on Drug Dissolution

PURPOSE

The purpose of the present study was to investigate the effect of food viscosity on the dissolution rate of a drug. There are two types of viscosity, macroviscosity and microviscosity. Macroviscosity affects the diffusion layer thickness, whereas microviscosity affects the molecular diffusion coefficient. The mass transfer coefficient (kc) in the intrinsic dissolution rate (IDR) depends on the viscosity (η) as kc ∝ ηa (a is an exponent on η). In theory, for rotating flow over a disk, if a thickener increases only macroviscosity, a = -1/6, and if it increases both macroviscosity and microviscosity equally, a = -7/6.

METHOD

Benzocaine was used as a model drug. Hydroxypropyl cellulose (HPC) and methylcellulose (MC) were employed as control thickeners that increase only macroviscosity. Sucrose was employed as a control thickener for both macroviscosity and microviscosity. The FDA breakfast homogenate (BFH) was diluted with distilled water or 1 mM HCl with/without pepsin digestion. The IDR value was measured by the paddle-over-disk method.

RESULTS

The η value of 30% BFH distilled water was 209 mPa∙s, about 300 times higher than distilled water. It was further increased by HCl (430 mPa∙s), and reduced by pepsin digestion (35 mPa∙s). The kc value was little affected by BFH (a = 0.00 to -0.09), slightly less than those in HPC (a = -0.19) and MC (a = -0.21). Sucrose decreased the kc value more significantly (a = -0.70).

CONCLUSION

The IDR and kc values of benzocaine were little affected by BFH, suggesting that BFH increased only macroviscosity.

In vitro and in silico methods to investigate the effect of moderately increasing medium viscosity and density on ibuprofen dissolution rate

Medium viscosity can affect drug dissolution rate, however, it is not usually considered in routine dissolution testing or less complex biorelevant media. The effects of moderately increasing medium viscosity on the in vitro and in silico dissolution of ibuprofen were investigated with two viscosity enhancing agents (VEA) (hydroxypropyl methylcellulose (HPMC) and sucrose), three viscosity levels (range 0.7-5.5 mPa.s), two solubilities and two fluid velocities in the paddle, flow-through and intrinsic dissolution apparatuses. A factorial design analysis highlighted which factors significantly affected key dissolution metrics. Experimental results in the flow-through apparatus (FTA) were compared with in silico dissolution profiles generated by an in-house simulation code (SIMDISSOTM). Increasing viscosity reduced the intrinsic dissolution rate of ibuprofen for both VEAs. The dissolution rate reduction was also observed in the FTA with sucrose, but less so with HPMC, suggesting particle wetting, motion and surface area effects. Particle motion simulations suggested reduced particle lifting times as viscosity increased, indicating an effect of viscosity on particle dispersal. The viscosity- and fluid density-mediated reduction in the dissolution rate observed with sucrose was accurately simulated by SIMDISSOTM, in particular at higher velocities. Velocity had a significant impact on dissolution rates in the paddle apparatus, with a significant viscosity-related reduction in dissolution observed in the low solubility-low velocity scenario. Even small increases in medium viscosity can reduce the dissolution rate of a BCS class II drug, and in silico particle motion and dissolution data can assist interpretation of particulate dissolution behaviour.

Evaluation and prediction of oral drug absorption and bioequivalence with food-drug interaction

This article reviews the impacts on the in vivo prediction of oral bioavailability (BA) and bioequivalence (BE) based on Biopharmaceutical classification systems (BCS) by the food-drug interaction (food effect) and the gastrointestinal (GI) environmental change. Various in vitro and in silico predictive methodologies have been used to expect the BA and BE of the test oral formulation. Food intake changes the GI physiology and environment, which affect oral drug absorption and its BE evaluation. Even though the pHs and bile acids in the GI tract would have significant influence on drug dissolution and, hence, oral drug absorption, those impacts largely depend on the physicochemical properties of oral medicine, active pharmaceutical ingredients (APIs). BCS class I and III drugs are high soluble drugs in the physiological pH range, food-drug interaction may not affect their BA. On the other hand, BCS class II and IV drugs have pH-dependent solubility, and the more bile acid secretion and the pH changes by food intake might affect their BA. In this report, the GI physiological changes between the fasted and fed states are described and the prediction on the oral drug absorption by food-drug interaction have been introduced.

Do Thickening Agents Used in Dysphagia Diet Affect Drug Bioavailability?

Swallowing oral solid dosage forms is challenging in patients with dysphagia who are at risk of aspiration or choking. The most common method to facilitate drug administration in dysphagia patients is to mix the powdered drug with a small amount of thickened water, however little is known about the effects of this method on in vivo bioavailability of drugs. This study aimed to evaluate the impact of thickened liquids on dissolution rate and bioavailability of levetiracetam as a model drug. Powdered commercial tablets of levetiracetam, carbamazepine, atenolol and cefixime were mixed with water thickened with two commercial thickeners, modified maize starch (MS) and xanthan gam (XG), at three thickness levels: nectar, honey and pudding in test groups, and mixed with only water in the control group. At the first stage, the effects of thickened water on in vitro drug release of 4 drugs (levetiracetam, carbamazepine, atenolol and cefixime) were tested by using dialysis membrane method. Addition of both thickeners significantly reduced the release of three drugs compared to the control group, except carbamazepine. Levetiracetam which had the highest solubility was chosen as the model drug for in vivo experiments. In the second stage, New Zealand albino female rabbits (n=24) were divided into two groups as: control group (water+drug, n=6) and test group (thickened water+drug, n=18). Powdered levetiracetam tablets were mixed with water thickened with XG (n=9, 1.2 %, 2.4 %, 3.6 %) and MS (n=9, 4 %, 6%, 8 %) at three thickness levels and administered to the rabbits by intragastric gavage. Blood samples were collected at 9 time points following administration. After two-weeks of wash-out, test groups were crossed over and sample collection was repeated. Blood samples were analysed using liquid chromatography with tandem mass spectrometry (LC-MS/MS). An in vitro-in vivo correlation (IVIVC) model was developed using in vitro drug dissolution (%) and in vivo plasma concentrations of levetiracetam for control group and test groups. The peak plasma concentration (C_max) was lower and time to reach C_max (t_max) was relatively higher in test groups compared to control group. The lowest C_max was detected at the highest thickness level, however, the differences between groups were not statistically significant (p=0.117 and p=0.495 for C_max and t_max, respectively). No significant difference in total amount of levetiracetam absorbed (AUC) was found between groups (p=0.215 and p=0.183 for AUC_infinity and AUC_last, respectively). The comparisons according to the type of thickener also revealed that pharmacokinetic parameters did not significantly differ between groups, except for a significantly lower C_max when drug was mixed with MS-thickened water at nectar consistency (1.2 %) compared to drug mixed with XG (4 %) at the same thickness level (p=0.038). A good correlation was observed between in vitro and in vivo data, which was characterized by higher r² values as the concentration of the thickening agents was increased, but not for all thickness levels studied, indicating an inability of this in vitro model to fully predict the in vivo response. These results suggest that regardless of the thickness level, the administration of levetiracetam with two commercial thickening agents commonly used in dysphagia for safe swallowing, do not affect the pharmacokinetic efficiency and thus, the bioavailability of the drug.

Bio-enabling strategies to mitigate the pharmaceutical food effect: a mini review

The concomitant administration of oral drugs with food can result in significant changes in bioavailability, leading to variable pharmacokinetics and considerable clinical implications, such as over- or under-dosing. Consequently, there is increasing demand for bio-enabling formulation strategies to reduce variability in exposure between the fasted and fed state and/or mitigate the pharmaceutical food effect. The current review critically evaluates technologies that have been implemented to overcome the positive food effects of pharmaceutical drugs, including, lipid-based formulations, nanosized drug preparations, cyclodextrins, amorphisation and solid dispersions, prodrugs and salts. Additionally, improved insight into preclinical models for predicting the food effect is provided. Despite the wealth of research, this review demonstrates that application of optimal formulation strategies to mitigate the positive food effects and the evaluation in preclinical models is not a universal approach, and improved standardisation of models to predict the food effects would be desirable. Ultimately, the successful reformulation of specific drugs to eliminate the food effect provides a panoply of advantages for patients with regard to clinical efficacy and compliance.

Effect of thickener on disintegration, dissolution and permeability of common drug products for elderly patients

Dysphagia is a very common problem suffered by elderly patients. The use of thickeners during administration in these patients helps to prevent difficulties with swallowing larger solid dosage forms. However, there are several indications when the thickeners may influence disintegration and dissolution processes of solid dosage forms, potentially affecting therapeutic efficacy. In this paper the effects of a commonly used thickener on tablet disintegration, dissolution and subsequent absorption of 6 formulated drugs frequently used in elderly patients (Aspirin, Atenolol, Acenocumarol, Candesartan, Ramipril and Valsartan) in two different administration conditions (intact tablet and crushed tablet) are reported. Disintegration times were determined using a modified disintegration test device. The presence of thickener leads to a pseudoplastic behavior with clearly increased viscosity values. The thickener was also shown to significantly affect the release processes (dissolution and disintegration), but not the permeability of the studied drugs. When tablets are crushed the effect of the thickener on drug dissolution is avoided. Consequently, crushing the tablets would be a recommendation for these drugs if the use of a thickener is necessary in patients with dysphagia.

Understanding the Potential for Dissolution Simulation to Explore the Effects of Medium Viscosity on Particulate Dissolution

Viscosity, influenced by medium composition, will affect the hydrodynamics of a dissolution system. Dissolution simulation methods are valuable tools to explore mechanistic dissolution effects, with an understanding of limitations of any simulation method essential to its appropriate use. The aims of this paper were a) to explore, using dissolution simulation, the effects of slightly viscous media on particulate dissolution and b) to illustrate approaches to, and limitations of, the dissolution simulations. A lumped parameter fluid dynamics dissolution simulation model (SIMDISSO™) was used to simulate particulate (20 and 200 μm diameter) dissolution in media with viscosity at 37 °C of water (0.7 mPa.s), milk (1.4 mPa.s) and a nutrient drink (12.3 mPa.s). Effects of flow rate, modality (constant vs pulsing), viscosity and gravitational and particle motion/sedimentation effects on simulated dissolution were explored, in the flow through and paddle apparatuses as appropriate. Shadowgraph imaging (SGI) was used to visualise particle suspension behaviour. Flow rate, hydrodynamic viscous effects and disabling particle motion and gravitational effects affected simulated dissolution of larger particles. SGI imaging revealed retention of particles in suspension in 1.4 mPa.s medium, which sedimented in water. The effect of diffusion adjusted for viscosity was significant for both particle sizes. The limitations of this 1D simulation approach would be greater for larger particles in low velocity regions of the paddle apparatus. Even slightly viscous media can affect dissolution of larger particles with dissolution simulation affording insight into the mechanisms involved, provided the assumptions and limitations of the simulation approach are clarified and understood.

Development of multi-layered gastric floating tablets based on konjac glucomannan: a modified calcium supplement with enhanced bioavailability

This study developed a gastric-floating delivery system of calcium based on konjac glucomannan (KGM).

Food for thought: formulating away the food effect - a PEARRL review

OBJECTIVES

Co-ingestion of oral dosage forms with meals can cause substantial changes in bioavailability relative to the fasted state. Food-mediated effects on bioavailability can have significant consequences in drug development, regulatory and clinical settings. To date, the primary focus of research has focused on the ability to mechanistically understand the causes and predict the occurrence of these effects.

KEY FINDINGS

The current review describes the mechanisms underpinning the occurrence of food effects, sheds new insights on the relative frequency for newly licensed medicines and describes the various methods by which they can be overcome. Analysis of oral medicines licensed by either the EMA or FDA since 2010 revealed that over 40% display significant food effects. Due to altered bioavailability, these medicines are often required to be dosed, rather restrictively, in either the fed or the fasted state, which can hinder clinical usefulness.

SUMMARY

There are clinical and commercial advantages to predicting the presence of food effects early in the drug development process, in order to mitigate this risk of variable food effect bioavailability. Formulation approaches aimed at reducing variable food-dependent bioavailability, through the use of bio-enabling formulations, are an essential tool in addressing this challenge and the latest state of the art in this field are summarised here.

Justification of disintegration testing beyond current FDA criteria using in vitro and in silico models

Drug product performance testing is an important part of quality-by-design approaches, but this process often lacks the underlying mechanistic understanding of the complex interactions between the disintegration and dissolution processes involved. Whereas a recent draft guideline by the US Food and Drug Administration (FDA) has allowed the replacement of dissolution testing with disintegration testing, the mentioned criteria are not globally accepted. This study provides scientific justification for using disintegration testing rather than dissolution testing as a quality control method for certain immediate release (IR) formulations. A mechanistic approach, which is beyond the current FDA criteria, is presented. Dissolution testing via United States Pharmacopeial Convention Apparatus II at various paddle speeds was performed for immediate and extended release formulations of metronidazole. Dissolution profile fitting via DDSolver and dissolution profile predictions via DDDPlus™ were performed. The results showed that Fickian diffusion and drug particle properties (DPP) were responsible for the dissolution of the IR tablets, and that formulation factors (eg, coning) impacted dissolution only at lower rotation speeds. Dissolution was completely formulation controlled if extended release tablets were tested and DPP were not important. To demonstrate that disintegration is the most important dosage form attribute when dissolution is DPP controlled, disintegration, intrinsic dissolution and dissolution testing were performed in conventional and disintegration impacting media (DIM). Tablet disintegration was affected by DIM and model fitting to the Korsmeyer-Peppas equation showed a growing effect of the formulation in DIM. DDDPlus was able to predict tablet dissolution and the intrinsic dissolution profiles in conventional media and DIM. The study showed that disintegration has to occur before DPP-dependent dissolution can happen. The study suggests that disintegration can be used as performance test of rapidly disintegrating tablets beyond the FDA criteria. The scientific criteria and justification is that dissolution has to be DPP dependent, originated from active pharmaceutical ingredient characteristics and formulations factors have to be negligible.

Computational Fluid Dynamics Simulation of Hydrodynamics and Stresses in the PhEur/USP Disintegration Tester Under Fed and Fasted Fluid Characteristics

Disintegration of oral solid dosage forms is a prerequisite for drug dissolution and absorption and is to a large extent dependent on the pressures and hydrodynamic conditions in the solution that the dosage form is exposed to. In this work, the hydrodynamics in the PhEur/USP disintegration tester were investigated using computational fluid dynamics (CFD). Particle image velocimetry was used to validate the CFD predictions. The CFD simulations were performed with different Newtonian and non-Newtonian fluids, representing fasted and fed states. The results indicate that the current design and operating conditions of the disintegration test device, given by the pharmacopoeias, are not reproducing the in vivo situation. This holds true for the hydrodynamics in the disintegration tester that generates Reynolds numbers dissimilar to the reported in vivo situation. Also, when using homogenized US FDA meal, representing the fed state, too high viscosities and relative pressures are generated. The forces acting on the dosage form are too small for all fluids compared to the in vivo situation. The lack of peristaltic contractions, which generate hydrodynamics and shear stress in vivo, might be the major drawback of the compendial device resulting in the observed differences between predicted and in vivo measured hydrodynamics.