36°

The drug OxyContin is an extended release form of oxycodone, which is a synthetic derivative of morphine.

All opiate medications affect receptors in the brain that are involved in the regulation of pain perception and mood, said Dr. Paul Topol of Southeast Psychiatry. The body naturally produces its own version of opioid compounds known as endorphins and enkalphins in response to stress and exertion, and oxycodone mimics the effects of these compounds in the brain, he said.

"As the dose increases, the effects go beyond pain relief and produce euphoria," he said. "Further increases begin to interfere with the parts of the brain responsible for maintaining alertness and regulating respiration."

Overdose results in loss of consciousness and the patient can stop breathing.

The margin between euphoria and overdose is narrow, Topol said.

"It becomes narrower as tolerance to the euphoric effects increases with regular use," he said. "The mechanism of tolerance is thought to do with the brain's response to chronically high levels of opiates. The number of opiate receptors in the brain diminishes over time. It is also thought that high levels of opiate reduces the body's own production of endorphins and enkalphins."

When an addict stops using, the brain gets a double whammy - the natural endorphins are suppressed and the number of receptors to pick them up has decreased.

The end result is that when someone is going through withdrawal, they have increased sensitivity to pain and depressed mood. And the opiate user will look for more.

Topol said sensitivity to euphoric effects of opiates and the speed the brain adapts to using them are important determinants of addiction. Unfortunately, Topol said, addiction comes as a surprise to most addicts, and most people only realize their vulnerability after the process is well under way.

The other big influence to the development of addiction is the frequency of use, Topol said. For many people, the risk of addiction increases incrementally with each subsequent use.

"For some people, the brain changes that come with chronic use of opiates appear to be irreversible," he said. "This likely accounts for the poor prognosis of heavy long-term users. There is no way to predict if you are going to become one of those people until you have become one."