for: Withdrawal (disambiguation) Withdrawal, also known as withdrawal/abstinence syndrome, refers to the characteristic signs and symptoms that appear when a drug that causes physical dependence is regularly used for a long time and then suddenly discontinued or decreased in dosage. The term can also, less formally, refer to symptoms that appear after discontinuing a drug or other substance (unable to cause true physical dependence) that one has become psychologically dependent upon.

Examples are:

• alcohol withdrawal syndrome
• delirium tremens
• benzodiazepine withdrawal syndrome
• methadone withdrawal symptoms
• SSRI discontinuation syndrome
• neonatal abstinence syndrome

Overview

The sustained use of many kinds of drugs causes reversible adaptations within the body that tend to lessen the drug's original effects over time, a phenomenon known as drug tolerance. To have these adaptations to a drug is to have a physical dependency on it, for when the drug is suddenly discontinued or decreased, the adaptations do not immediately disappear. Unopposed by the drug, the adaptations appear as withdrawal signs and symptoms that are generally the opposite of the drug's direct effects. Depending primarily on the drug's elimination half-life, withdrawal symptoms can appear within a few hours to several days after discontinuation.

The withdrawal symptoms associated with many recreational drugs are well-known. However, many drugs that do not generally cause euphoria, and are therefore not generally abused or thought of as addictive, also induce physical dependence with associated withdrawal. Examples include beta blockers, corticosteroids such as cortisone, many anticonvulsants and most antidepressants. Nevertheless, sudden withdrawal from these medications can be harmful or even fatal; this is why many prescription labels explicitly warn the patient not to discontinue the drug without doctor approval.

Withdrawal from drugs of abuse

Central to the role of nearly all drugs that are commonly abused to produce euphoria is the nucleus accumbens, the brain's "pleasure center". Neurons in the nucleus accumbens use the neurotransmitter dopamine, so while specific mechanisms vary, nearly every drug of abuse either stimulates dopamine release or enhances its activity, directly or indirectly. Sustained use of the drug results in less and less stimulation of the nucleus accumbens until eventually it produces no euphoria at all. Discontinuation of the drug then produces a withdrawal syndrome characterized by dysphoria — the opposite of euphoria — as nucleus accumbens activity declines below normal levels Fact: date=May 2008

Withdrawal symptoms can vary significantly among individuals, but there are some commonalities. Subnormal activity in the nucleus accumbens is often characterized by depression, anxiety and craving, and if extreme can help drive the individual to continue the drug despite significant harm — the definition of addiction — or even to suicide Fact: date=May 2008