After medicine is swallowed, it must be absorbed into the blood so it can move throughout the body. The process of absorbing, digesting, and excreting a medicine or food is called metabolism. The way the body metabolizes a particular medicine affects how often it must be taken. It also determines whether it will interact with other medicines or be affected by conditions such as liver disease.

Tegretol-XR is a form of the seizure medicine carbamazepine. Carbamazepine and many other medicines are broken down (digested) in the liver. If the person takes both Tegretol-XR and another medicine that is digested in the liver, things can get complicated. How well each medicine works and how quickly it leaves the body may be changed.

This is why the doctor needs to know about everything that a person takes—not just prescription medicines but even things like vitamins, herbs, and aspirin!