All too often, when a person takes a pill full of a potent and effective drug, the drug passes straight through the body, not reaching the organ where it is needed — a waste of money and inconvenient if it is a cold medicine, but potentially dire if it is a treatment for a serious illness. Polymer chemists at Virginia Tech and pharmaceutical scientists at Purdue University have teamed up to design a solution.

Their research to identify, understand, and create new polymer additives that enhance the ability of orally administered drugs to reach the bloodstream has been published in a series of journals. In a special issue of the Elsevier journal Carbohydrate Polymers, they introduced an all-natural polymer that can be used with a range of medicines to prevent crystallization during transport and storage; it then traverses the digestive tract until the still fully potent medicine is released from the polymer in the small intestine, where it is best absorbed into the bloodstream.

Many important drugs are like table salt; they crystallize easily. When they do, the crystals are stubbornly difficult to dissolve. They crystallize instead of remaining dispersed, whether in the pill or after release in the digestive tract. Many medicines locked into crystals don’t dissolve fast enough to work properly. If that happens, they can’t reach their target.

Polymers are introduced to interfere with crystallization. “But the polymers that are presently FDA approved are not effective in meeting all the challenges,” said Edgar. “They may prevent a process called nucleation but not stop growth of the crystal if it gets started. Or they may not continue to work after a period of time or if conditions are too hot or too damp. We needed to design a better polymer.”

Imagine sugar dissolved in water. If a bit of dust is introduced, it can lead to nucleation — the sugar sticks to the dust — and then crystal growth. In this example, the polymer would cover the dust mote and repel the sugar molecules, preventing nucleation.

The Virginia Tech and Purdue groups have discovered that the effective design for pharmaceutical applications is cellulose omega-carboxyesters, which are cellulose esters that the researchers have enhanced with acids that already occur in the human body.

“For example, adipic acid, a natural acid present in sugar cane, can be attached to cellulose acetate to make an adipate ester,” said Edgar. “Cellulose acetate is already used in many medicines that people take today; it controls the rate of release of the drug.”

The researchers figured out how to make omega-carboxyesters that keep different kinds of medicines dispersed and prevent them from crystallizing — in other words, creating pills with higher bioavailability.

The final neat trick, after creating a polymer that binds the medicines so they cannot crystallize, is to make sure that polymer also knows when to let go.

Cellulose adipate esters and their cousin omega-carboxyester, cellulose acetate suberate, are no more complicated to make than those in adhesive tape and other inexpensive products, except that they are made with a different set of natural acids.

This story is reprinted from material from
Virginia Tech, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.