30 September 2022

Pill-Taking Posture

It’s a wild guess, but I bet you didn’t think about your posture the last time you took a pill. Well, maybe you should have. Posture has a significant effect on how quickly our bodies absorb a pill’s contents. 

Welcome back. Popping a pill is the most common choice for drug administration, offering convenience, low cost and high patient compliance.

Most pills don’t start working until they’ve dissolved and passed through the stomach into the duodenum, the first part of the small intestine. The closer a swallowed pill lands to the last part of the stomach, the faster it starts to dissolve and empty its contents into the duodenum.

Simple stomach diagram (from pharmacyimages.blogspot.com/2020/09/Simplestomachdiagram-Stomachstructure-stomachanatomy.html).
Posture is critical If you’d like to get the pill down there fast. How critical? That was investigated by a team of researchers affiliated with Johns Hopkins University.

The researchers used in-vivo imaging data available from the Virtual Population library to construct StomachSim, an anatomical model of a human stomach.

Using StomachSim, they observed and quantified pill dissolution, mixing in the stomach, and gastric emptying of the dissolved active pharmaceutical ingredient into the duodenum, modulated by gastric motility, physical properties of the pill and stomach contents.

StomachSim also allowed tracing the trajectory of the pill motion, which is induced by a complex interplay of stomach motility, gastric fluid dynamics, gravity and, yes, posture.

Testing Postures
To compare the effect of posture on drug availability, they considered four different postures
keeping other parameters constant: upright, leaning right, leaning left and leaning back.

Rather than rotate the stomach with posture, they changed the direction of the gravitational force. Because the pill is denser than the dissolution medium, the effect of direction significantly affects pill motion and thus the rate of dissolution and pharmaceutical ingredient release. 

Diagram showing original position and different relative positions of the stomach with respect to the direction of gravity (Fig. 4 from aip.scitation.org/doi/full/10.1063/5.0096877).
Swallowing pills while lying on the right side was by far the best posture, sending pills into the deepest part of the stomach 2.3 times faster than even an upright posture. Lying on the left side was the worst. A pill that needs 10 minutes to dissolve when lying on the right side, could take 23 minutes to dissolve in an upright posture and over 100 minutes when lying on the left side.

Volumetric distributions of dissolved active pharmaceutical ingredients in the stomach and duodenum regions for different postures at three time periods (t, seconds)(from Fig. 5 of aip.scitation.org/doi/full/10.1063/5.0096877).
The team also considered pill dissolution by stomachs that aren’t functioning at full strength due to gastroparesis caused by diseases such as diabetes and Parkinson’s Syndrome. The impact of stomach disease on drug dissolution was similar to that of posture.

Wrap Up
The findings have important implications when accounting for posture in clinical studies of drug dissolution and to consider posture as a factor modulating the release of a pharmaceutical concentration. This is particularly relevant for narrow absorption window drugs, absorbed mainly in the upper part of the gastrointestinal tract. It also has important implications for the rate of drug absorption by bedridden patients or elderly adults.

Next on the research team’s agenda are how changes in the biomechanics of the stomach affect drug absorption, how food is processed in the stomach and the effect of posture and gastroparesis on food digestion. Stay tuned and thanks for stopping by.

Study of effects of posture in Physics of Fluids journal: aip.scitation.org/doi/full/10.1063/5.0096877
Article on study on EurekAlert! website: www.eurekalert.org/news-releases/961853
Virtual Population library: www.semanticscholar.org/paper/Development-of-a-new-generation-of-high-resolution-Gosselin-Neufeld/d8b3865ca3ef524f9177f15e73b5747365ab1141


  1. OK, so if taking a pill lying down, right side is best. But did the study look at taking med while standing upright? What did I miss?