Opiate withdrawal is an acute state caused by cessation or dramatic reduction of use of opiate drugs that has been heavy and prolonged (several weeks or longer).

Opiates include heroin, morphine, codeine, Oxycontin, Dilaudid, methadone, and others. The reaction frequently includes sweating, shaking, headache, drug craving, nausea, vomiting, abdominal cramping, diarrhea, inability to sleep, confusion, agitation, depression, anxiety, and other behavioral changes.

About 5% of the population is believed to misuse opiates -- including illegal drugs like heroin and legal drugs used to treat pain, such as Oxycontin.

These drugs can cause physical dependence, which means that the body reduces production of its own natural opioids (endorphins and enkephalins) and begins to rely on the drug to manage the functions of these natural brain chemicals.

The time it takes to become physically dependent varies significantly. Some people can take opiate drugs for a month or longer and experience no withdrawal signs, while others develop withdrawal symptoms after ending only a week or so of daily use.

When the drugs are stopped, the body needs time to begin providing neccessary amounts of the natural opioids again and withdrawal symptoms result. Withdrawal from opiates can occur whenever any chronic use is discontinued or reduced.

Note: physical dependence is not addiction, which is defined as compulsive use of a substance despite negative consequences. Pain patients who use opiates as prescribed for long periods of time can develop physical dependence. However, because they don't have the psychological attachment to the drug seen in addiction, withdrawal symptoms are often less distressing.

Some people even withdraw from opiates after hospitalization for painful conditions without realizing what is happening to them. They think they have the flu, and because they don't know that opiates would fix the problem, they don't crave the drugs.