Why do I have to take some medications every four hours but others only once a day?

Why do I have to take some medications every four hours but others only once a day?
Just as there’s no such thing as a “generic” person, no two people process the same medication in just the same way…

Because some drugs don’t last as long in the body as others, says Steven Tannenbaum, the Underwood-Prescott professor of Biological Engineering. Every drug, whether it’s swallowed, inhaled, or injected, is absorbed into the blood stream, distributed throughout the body, broken down in the liver and other organs, and, finally, excreted out of the body. But no two drugs are treated the same.

Understanding how drugs can be taken less frequently and still have the same affect is a task that many engineers like Tannenbaum are taking on. “If you have to take a drug several times a day,” he says, “you almost always forget to take a dose.”

Along with collaborators like Linda Griffith, a professor of biological and mechanical engineering, Tannenbaum is beginning to understand the details of how the human body processes a medication. Griffith’s “liver-on-a-chip” technology grows liver cells on a three-dimensional scaffold. The cells are then bathed in different mixes of drugs, and the results help engineers understand how enzymes break down different drugs, and at what rates these reactions happen.

Then Tannenbaum, using the analytical tools of his lab, can look very closely at what is left over from this process. A better understanding of the fate of the drug and its leftover fragments means getting a better grasp of how long the drug will last, and how it will affect the body.

Engineers are thinking about ways to design drugs that can break down more slowly or more quickly – depending on the medication, or depending on the patient. Some drugs can damage cells if they circulate in the body for too long, or they can break down into compounds that are harmful if they aren’t cleared fast enough.

And different people respond differently to different medications, Tannenbaum says. “Some may need more, some less, and some may need a different drug.” Eventually personalized medicine will allow a doctor to quickly figure out each patient’s individual sensitivity levels and prescribe customized medications, but, Tannenbaum admits, “that’s a long way off.” – Elizabeth Dougherty

- Posted: 

May 12, 2009