Prescription pain medications: what you need to know.

• Position: HEADS UP: REAL NEWS ABOUT DRUGS AND YOUR BODY - Essay

When used as directed by a doctor, powerful prescription pain medications called opioids (pronounced OH-pee-oyds) have helped millions of people cope with serious pain. But when used incorrectly, they can be addictive and deadly.

Some pain can be treated by over-the-counter medications such as Advil[R] and Tylenol[R]. But for pain from surgery, cancer, or serious injuries, doctors often prescribe the most powerful medications available--opioids. Opioid medications, such as Vicodin[R] and OxyContin[R], are part of a class of drugs that resemble opioid chemicals our bodies make. In nature, opioids are found in the poppy plant, which is the source of some opioid medications as well as illegal opioids such as heroin.

Opioid medications are made to specific standards and regulated by the government for safety. But opioid medications can be powerfully addictive and can cause an overdose if not taken correctly. How is it that a medication that is so effective at relieving pain and helpful in healing can be so harmful when misused? The answer comes from how opioids work in the body.

Opioid Drugs: Master Impersonators

Opioid drugs, including medications and illegal drugs, are chemically very similar to endorphins, one of the body's natural opioids. When opioid drugs are taken, they use opioid receptors that are normally accessed by endorphins to tap into the body's systems. However, opioid drugs are more powerful than the opioids the body makes, so they trigger much stronger reactions.

Opioids and Pain

Endorphins naturally block pain by binding to opioid receptors in the spinal cord and other parts of the nervous system. Opioid drugs mimic endorphins but cause a much stronger painblocking signal. This is why opioid medications are prescribed for serious pain.

Opioids and Addiction

Opioid receptors are also found in the part of the brain that releases dopamine. Dopamine causes us to feel pleasure and to remember which behaviors produced this feeling. For example, endorphins released during physical activity can prompt a surge of dopamine, known as a "runner's high." Opioid drugs, however, cause a larger flood of dopamine to be released. The brain remembers the "high" and over time, with repeated abuse, develops an altered dopamine response. The brain begins to crave the extra intensity only an opioid drug can deliver, which can lead to addiction.

Opioids and Overdose

Opioid receptors in the brain and brain stem also regulate breathing. In proper...