When you have a headache and reach for the pain reliever, you probably don’t think about the position of your body when you take the pill. But a new Johns Hopkins University study finds that your posture can make a big difference in how quickly your body absorbs the drug, and improper posture can delay how quickly the drug is broken down and absorbed — by about an hour.
The findings are based on what is believed to be the first model to simulate the mechanics of drug dissolution in a human stomach.
“We were very surprised that posture had such a huge effect on the dissolution rate of a pill,” said senior author Rajat Mittal, a Johns Hopkins engineer and fluid dynamics expert. “I never thought about whether I was doing it right or not, but now I will definitely think about it every time I take a pill.”
The work was recently published in Physics of liquids.
In recent years, models have been created to authentically represent the work of several major organs, especially the heart. The model developed by the team, called StomachSim, appears to be one of the first that can conduct a realistic simulation of the human stomach. Combining physics with biomechanics and fluid mechanics, StomachSim mimics what happens in the stomach as it digests food, or in this case medicine.
Most pills don’t begin to work until the stomach expels its contents into the intestines. So the closer a pill lands to the lower part of the stomach, the antrum, the faster it begins to dissolve and empty its contents through the pylorus into the duodenum, the first part of the small intestine. If you are aiming a pill at this part of the stomach, the position is critical for both gravity and the natural asymmetry of the stomach.
The team tested four postures. Taking pills while lying on the right side was definitely the best, sending the pills to the deepest part of the stomach to achieve a dissolution rate 2.3 times faster than even an upright position. Lying on the left side was the worst. The team was very surprised to find that if a pill takes 10 minutes to dissolve on the right side, it can take 23 minutes to dissolve in an upright position and over 100 minutes when lying on the left side.
“For elderly, sedentary or bedridden people, whether they turn left or right can have a huge impact,” Mittal said.
Standing upright was a decent second choice, essentially tied in effectiveness to lying flat on the back.
The team also considered what stomachs not functioning at full capacity meant for pill dissolution. Even a small change in the state 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, such as gastroparesis caused by diabetes or Parkinson’s disease, on drug dissolution is similar to that of posture—underscoring how significant a difference posture can make.
“The posture itself has such a big impact that it’s equivalent to someone’s stomach having a very significant dysfunction in terms of dissolving the pills,” Mittal said.
Future work will try to predict how changes in stomach biomechanics affect how the body absorbs drugs, how food is processed in the stomach, and the effect of posture and gastroparesis on digestion.
Johns Hopkins authors include doctoral student Sharon Kuhar; Associate Professor Jung-Hee Seo; and Jay Pasricha, professor of medicine. The work was supported by National Science Foundation CBET 2019405 and National Institutes of Health 5R21GM139073-02.