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Mechanism-based modeling of biological processes involved in oral absorption
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

For orally administered drugs, the rate and extent of absorption are governed by the physiology of the gastrointestinal tract, the characteristics of the dosage form and the physico-chemical properties of the drug. This thesis primarily aimed to improve the mechanistic understanding and the predictability of processes involved in the absorption of orally administered drugs using a population modeling approach. A secondary aim was to propose an optimized dosing regimen for first line anti-tuberculosis drugs in underweight Indian children.

A model characterized the effect of pH, mechanical stress and formulation on in vitro extended release (ER) tablet erosion. The model was further used in combination with anatomical tablet location data to predict the in vivo erosion dynamics. The proposed approach could help address challenges related to the development of future ER formulations.

Gastric emptying regulates the rate of entry of nutrients into the small intestine. Bile acids are essential for the intestinal absorption of lipophilic drugs, but the determination of their local intestinal concentrations is difficult. A modeling framework was developed to characterize the relationships between nutritional intake, rate of gastric emptying, gallbladder emptying–refilling patterns and plasma concentrations of bile acids. This modeling framework could be used in combination with systems pharmacology models to predict the drug-drug interactions and food effects associated with gastric emptying, as well as to link the postprandial changes in plasma bile acid concentrations to the variability in drugs’ absorption.

Optimal doses of first-line antituberculosis drugs have not been firmly established. In an underweight Indian children population, the pharmacokinetic-pharmacodynamic model identified rifampin as single predictor of unfavorable treatment outcome. Children with low body weight and/or HIV coinfection had a higher probability of unfavorable treatment outcome. Doses increase were proposed and could provide crucial information for future guidelines.

In summary, the developed models enabled the prediction of the in vivo erosion profile of ER formulations based on in vitro dissolution data. A modeling framework predicted the postprandial gastric emptying rate and enterohepatic circulation of bile acids. Finally, a model-based approach was used to identify risk factors and propose optimized dose recommendations in tuberculosis-infected Indian children.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. , p. 64
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Pharmacy, ISSN 1651-6192 ; 246
Keywords [en]
absorption, bile acids, enterohepatic circulation, food effect, gallbladder, in vitro in vivo correlation; NONMEM, pediatrics, pharmacometrics, tuberculosis
National Category
Health Sciences
Research subject
Pharmaceutical Science
Identifiers
URN: urn:nbn:se:uu:diva-340238ISBN: 978-91-513-0225-6 (print)OAI: oai:DiVA.org:uu-340238DiVA, id: diva2:1178146
Public defence
2018-03-16, A1:111a, Biomedicinskt centrum, Husargatan 3, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2018-02-22 Created: 2018-01-29 Last updated: 2018-03-07
List of papers
1. In Vitro and In Vivo Modeling of Hydroxypropyl Methylcellulose (HPMC) Matrix Tablet Erosion Under Fasting and Postprandial Status
Open this publication in new window or tab >>In Vitro and In Vivo Modeling of Hydroxypropyl Methylcellulose (HPMC) Matrix Tablet Erosion Under Fasting and Postprandial Status
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2017 (English)In: Pharmaceutical research, ISSN 0724-8741, E-ISSN 1573-904X, Vol. 34, no 4, p. 847-859Article in journal (Refereed) Published
Abstract [en]

To develop a model linking in vitro and in vivo erosion of extended release tablets under fasting and postprandial status. A nonlinear mixed-effects model was developed from the in vitro erosion profiles of four hydroxypropyl methylcellulose (HPMC) matrix tablets studied under a range of experimental conditions. The model was used to predict in vivo erosion of the HPMC matrix tablets in different locations of the gastrointestinal tract, determined by magnetic marker monitoring. In each gastrointestinal segment the pH was set to physiological values and mechanical stress was estimated in USP2 apparatus rotation speed equivalent. Erosion was best described by a Michaelis-Menten type model. The maximal HPMC release rate (V-MAX) was affected by pH, mechanical stress, HPMC and calcium hydrogen phosphate content. The amount of HPMC left at which the release rate is half of V-MAX depended on pH and calcium hydrogen phosphate. Mechanical stress was estimated for stomach (39.5 rpm), proximal (93.3 rpm) and distal (31.1 rpm) small intestine and colon (9.99 rpm). The in silico model accurately predicted the erosion profiles of HPMC matrix tablets under fasting and postprandial status and can be used to facilitate future development of extended release tablets.

Keywords
food effect, hydroxypropyl methylcellulose, in vitro in vivo correlation, magnetic marker monitoring, NONMEM
National Category
Pharmaceutical Sciences
Identifiers
urn:nbn:se:uu:diva-321446 (URN)10.1007/s11095-017-2113-7 (DOI)000396065400016 ()28155077 (PubMedID)
Available from: 2017-05-05 Created: 2017-05-05 Last updated: 2018-01-29
2. Mechanism-Based Modeling of Gastric Emptying Rate and Gallbladder Emptying in Response to Caloric Intake
Open this publication in new window or tab >>Mechanism-Based Modeling of Gastric Emptying Rate and Gallbladder Emptying in Response to Caloric Intake
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2016 (English)In: CPT-PHARMACOMETRICS & SYSTEMS PHARMACOLOGY, ISSN 2163-8306, Vol. 5, no 12, p. 692-700Article in journal (Refereed) Published
Abstract [en]

Bile acids released postprandially modify the rate and extent of absorption of lipophilic compounds. The present study aimed to predict gastric emptying (GE) rate and gallbladder emptying (GBE) patterns in response to caloric intake. A mechanism-based model for GE, cholecystokinin plasma concentrations, and GBE was developed on data from 33 patients with type 2 diabetes and 33 matched nondiabetic individuals who were administered various test drinks. A feedback action of the caloric content entering the proximal small intestine was identified for the rate of GE. The cholecystokinin concentrations were not predictive of GBE, and an alternative model linking the nutrients amount in the upper intestine to GBE was preferred. Relative to fats, the potency on GBE was 68% for proteins and 2.3% for carbohydrates. The model predictions were robust across a broad range of nutritional content and may potentially be used to predict postprandial changes in drug absorption.

National Category
Pharmaceutical Sciences
Identifiers
urn:nbn:se:uu:diva-314421 (URN)10.1002/psp4.12152 (DOI)000390923300006 ()
Funder
EU, FP7, Seventh Framework Programme
Available from: 2017-02-06 Created: 2017-02-02 Last updated: 2018-01-29Bibliographically approved
3. Model-based prediction of plasma concentration and enterohepatic circulation of total bile acids in humans
Open this publication in new window or tab >>Model-based prediction of plasma concentration and enterohepatic circulation of total bile acids in humans
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(English)Manuscript (preprint) (Other academic)
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-340234 (URN)
Available from: 2018-01-28 Created: 2018-01-28 Last updated: 2018-01-29
4. Suboptimal Antituberculosis Drug Concentrations and Outcomes in Small and HIV-Coinfected Children in India: Recommendations for Dose Modifications
Open this publication in new window or tab >>Suboptimal Antituberculosis Drug Concentrations and Outcomes in Small and HIV-Coinfected Children in India: Recommendations for Dose Modifications
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(English)In: Article in journal (Refereed) Epub ahead of print
National Category
Infectious Medicine
Identifiers
urn:nbn:se:uu:diva-340236 (URN)
Funder
Swedish Research Council, 521-2011-3442
Available from: 2018-01-28 Created: 2018-01-28 Last updated: 2018-01-29

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