To test pill coatings, try a stomach in a flask

A teen investigates which type of pill dissolves fastest in the gut


Tablets (in white) may dissolve in the stomach fastest, while compressed caplets (in orange, blue and pink) may last longer, a teen found.


LOS ANGELES, Calif. — Pills come in all sorts of shapes and sizes. Some are coated, and some are not. Roshni Sen, 17, wondered if a pill’s coating can affect how long it takes for the pill to break down in the body. To investigate, this senior at the Academy of Science and Technology at The Woodlands College Park in Texas created a “stomach” in a flask. She showed that different types of pills dissolve in different spots in the digestive tract. And that might affect which bottle you would want to reach for when you’ve got aches and pains.

Roshni presented her results at the Intel International Science and Engineering Fair (ISEF). Created by Society for Science & the Public and sponsored by Intel, the yearly fair brings high school students from all over the world together to share their research projects. (SSP also publishes Science News for Students and this blog.)

The teen became curious about how quickly pills dissolve after reading about a new type of pill that was supposed to release medicine inside the body at a constant rate. “I found this paper online talking about this new kind of pill that biomedical engineers made that has a porous outer coating,” Roshni says. It could make a pill’s effects last longer and be more consistent. Realizing how important a coating could be, she soon decided to do an experiment to find out how quickly the different types of pills now for sale dissolved in the stomach and small intestine.

Those pills now on the market come in many shapes and sizes, and with different coatings. Some are liquid inside a gel, or powder inside a gel caplet. Others are tablets or compressed caplets with shiny coatings. This can affect how quickly the medicine inside makes its way into someone’s bloodstream.

The teen worked with a drug that’s used to treat fever and pain. It’s available at any pharmacy and best known by the brand name Tylenol. (Its generic name is acetaminophen and paracetamol, depending on what country you are in.)  Most importantly, Roshni explains, “it comes with all the different kinds of coatings I needed.”

She wanted to examine four common pill coatings. A tablet is the most basic. “It essentially has no coating other than the one that just holds it together,” Roshni says. Compressed caplets have a hard, shiny coating. Gel caplets have a gel coating around a powder, and soft gels are made with a gel coating around a liquid.

Roshni Sen presents her project at Intel ISEF.B. Brookshire/SSP

To test how fast the pills dissolved, Roshni had to come up with a stand-in for the human digestive system. So she created models — simulations — of the stomach and small intestine with acidic solutions in flasks.

The stomach breaks food down so its nutrients can be absorbed by the body. Because of this, the stomach is full of enzymes and acid. The stomach has a pH of around 2. That’s about as acidic as lemon juice or vinegar. The small intestine, where most of the nutrients in food get absorbed, uses mostly enzymes, not acid, to finish digesting the food from the stomach. It is a strong base, with a pH of about 8. That’s about as basic as baking soda. To mimic these environments, Roshni prepared three beakers. One beaker matched the pH of the stomach. Another matched the pH of the small intestine. The third, her ­control, was pure water, which has a pH of 7.

To mimic the body’s temperature, she heated the beakers to 37° Celsius (98.6° Fahrenheit). She added a small stir-bar in each to keep the mixtures moving. This would stand in for the movement in the stomach and small intestine that mixes food and keeps it moving along.

Working in her school’s chemistry lab, Roshni placed a pill in each beaker. She then waited to see how long it took for the pill to completely dissolve. She repeated the experiment five times for each pill type in each beaker.

In water, all of the pills took more than an hour to dissolve. But there were differences in the acidic “stomach.” The tablets, which didn’t have much of a coating, dissolved the fastest, in about 12 to 13 minutes. The soft gels lasted a little longer, taking 15 to 16 minutes to dissolve, while the gel caplets took 18 to 20 minutes. Compressed caplets proved most hardy. They took 24 to 25 minutes to dissolve.

But Roshni got a surprise when she tried to dissolve her pills in her “intestine” flask. The tablets, soft gels and gel caplets took much longer to dissolve in the basic solution, between 28 and 36 minutes. But the compressed caplets, which withstood the strong acid of the stomach, dissolved quickly in the “small intestine,” in 13 to 15 minutes.

Compressed caplets are covered in an extra coating. It protects the pill from the stomach acid. “The main purpose is to elongate the process,” Roshni explains, making sure the pill does not dissolves until it reaches the small intestine. Why? If a pill dissolves in the stomach, the acid there might also break down some of the drug before it can be absorbed. That would make the pill less effective. Waiting to dissolve in the small intestine may ensure that more of the drug makes it into the bloodstream.

Tablets and soft gels could begin to treat pain and fever faster because they dissolve more quickly, Roshni concludes. But they also might be less effective, because some of their medicine will be lost in the stomach. So in some cases, the compressed caplets may prove more effective, she says.

Drug companies design medicines with different coatings for different purposes. Tablets and soft gels may be useful for quick relief. Compressed caplets, in contrast, may bring longer relief.

In the end, what kind of pill you take probably depends on what your needs are. “A lot of people just take a pill and hope it works and kind of forget about it,” the teen says. She hopes that her experiment will help spread knowledge about why different pill coatings exist and what they can do.

And when she’s in need, Roshni prefers speed. “I told my mom I won’t take gel caps or compressed caplets anymore,” she says. “I’m going to take soft gels.”

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Bethany Brookshire was a longtime staff writer at Science News Explores and is the author of the book Pests: How Humans Create Animal Villains. She has a Ph.D. in physiology and pharmacology and likes to write about neuroscience, biology, climate and more. She thinks Porgs are an invasive species.

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