The conclusions are based on what is thought to be the first model to replicate how a drug dissolves in the human stomach. “We were very surprised that posture had such an immense effect on the dissolution rate of a pill,” said senior author Rajat Mittal, a Johns Hopkins engineer and an expert in fluid dynamics. “I never thought about whether I was doing it right or wrong but now I’ll definitely think about it every time I take a pill.” Their findings were recently published in the journal Physics of Fluids. In recent years, models that accurately represent the working of various important organs, most notably the heart, have been developed. The team’s model, StomachSim, appears to be one of the first to be able to conduct realistic simulations of the human stomach. StomachSim simulates what happens within a stomach as it breaks down food or, in this instance, medicine by fusing physics, biomechanics, and fluid mechanics. The majority of pills don’t start working until the stomach passes its contents into the intestine. As a result, the closer a pill falls to the antrum, the quicker it begins to break down and unload its contents into the duodenum, the first part of the small intestine. If you’re aiming a pill for this part of the stomach, your posture is crucial in order to take use of gravity as well as the inherent asymmetry of the stomach. Four postures were tested by the team. Taking tablets while resting on the right side was by far the most effective, sending pills into the deepest part of the stomach and achieving a dissolution rate that was 2.3 times quicker than even an upright posture. The worst was lying on the left side. The team was astounded to discover that if a tablet dissolves in 10 minutes on the right side, it may take up to 23 minutes in an upright posture and over 100 minutes while laying on the left side. “For elderly, sedentary or bedridden people, whether they’re turning to left or to the right can have a huge impact,” Mittal said. Standing upright was a decent second choice, essentially tied in effectiveness with lying straight back. The team also considered stomachs that aren’t functioning at full strength due to gastroparesis caused by diseases such as diabetes and Parkinson’s Syndrome meant for pill dissolution. Even a small change in the conditions of the stomach can lead to significant differences in the outcome of an oral drug, said lead author Jae Ho “Mike” Lee, a former postdoctoral researcher at Johns Hopkins. The impact of stomach disease on drug dissolution was similar to that of posture—which underscores how significant a difference posture makes. “Posture itself has such a huge impact it, it’s equivalent to somebody’s stomach having a very significant dysfunction as far as pill dissolution is concerned,” Mittal said. Future work will attempt to predict how the changes in the biomechanics of the stomach affect how the body absorbs drugs, how food is processed in the stomach, and the effect of posture and gastroparesis on food digestion. Reference: “Computational modeling of drug dissolution in the human stomach: Effects of posture and gastroparesis on drug bioavailability” by J. H. Lee, S. Kuhar, J.-H. Seo, P. J. Pasricha and R. Mittal, 9 August 2022, Physics of Fluids.DOI: 10.1063/5.0096877 The study was funded by the National Science Foundation and the National Institutes of Health.
