Body posture, motility affect how stomach absorbs pills, study says

Aug. 9 (UPI) -- Using a computer simulation of the stomach, researchers at Johns Hopkins University have found that changes in body posture may have a significant effect on the emptying rate of a pill's active ingredient into the duodenum.

Simulations showed that postural changes can potentially have up to an 83% effect on the pill's absorption, according to their National Institutes of Health-funded study.

Its findings were published Tuesday in Physics of Fluids, the American Institute of Physics journal.

The scientists also found that problems with gastroparesis, a condition that affects the normal spontaneous movement of stomach muscles, also may significantly reduce the pill's dissolution and the emptying of its active ingredient into the duodenum.

In their paper, the researchers note that taking pills by mouth is most common because it has the advantages of being convenient, low cost and results in high patient compliance.

However, they note that the oral route is actually the most complex way for an active pharmaceutical ingredient to enter and be absorbed by the body, dependent on the interplay of stomach contents and motility, or muscle contractions, as well as gastric fluid dynamics.

Moreover, it's difficult to assess the how pills dissolve and how the rate is modulated by gastric motility, the pill's physical properties and the stomach's contents.

For their analysis, the scientists created what they describe as "a biomimetic in-silico simulator," called "StomachSim," based on the human stomach's anatomy and function.

Using this computer program simulator, they investigated and quantified the effect of body posture and stomach motility on the amount of the drug absorbed for an active effect.

Standing upright when taking a pill "is a good posture, of course," since the stomach is asymmetrically positioned and this position slides pills toward the stomach's exit, Rajat Mittal, professor of mechanical engineering at Johns Hopkins University, the study's corresponding author, told UPI in a phone interview.

If a person lies down to take the pill, because of the asymmetry of the stomach's positioning, the drug's dissolution slows down somewhat compared to standing upright, said Mittal, who also is a professor of medicine at Johns Hopkins' School of Medicine.

If a person turns and lies on their right side, the pill arrives at the stomach's antral region more quickly -- so lying down on the right side of the body speeds up the pill's absorption.

However, lying down on the left side of the body slows the pill's dissolution significantly.

Mittal said he was surprised to find that lying down on the left side "was equivalent to very serious gastric dysfunction" in terms of pill absorption into the body.

According to Mittal, the U.S. Pharmacopeia and Food and Drug Administration test a new pill's dissolution using a small chamber containing a paddle to stir the contents. "Our contention is this is a very inaccurate scenario," Mittal said, "because the stomach doesn't have a stirrer like this device."

Instead, the scientists hope that one day a computer simulator, based on the laws of physics and fluid mechanics, is used to determine how the drug dissolves.

"So, we propose moving toward computer simulations, which mimic the stomach better than these devices," he said.

Previously, the researchers have used the computer program simulation to analyze cardiovascular problems and air flow in the lungs, Mittal said.