Physical dependence

Physical dependence describes increased tolerance of a drug combined with a physical need of the drug to function. Abrupt cessation of the drug is typically associated with negative physical withdrawal symptoms.

Physical dependence is distinguished from addiction. While addiction tends to describe psychological and behavioral attributes, physical dependence is defined primarily using physical and biological concepts.

Symptoms
Persons physically dependent on a drug typically require larger doses of a drug over time to attain the same effect, a condition known as drug tolerance. Additionally, withdrawal of the drug produces symptoms including nausea, anxiety, hallucinations, body aches, and excessive sweating.

Drugs that cause physical dependence

 * alcohol
 * opiates such as morphine, heroin, codeine, and oxycodone
 * benzodiazepines such as valium, lorazepam, alprazolam, and clonazepam
 * barbiturates such as phenobarbital, amobarbital, and methylphenobarbital
 * nicotine
 * caffeine

Amphetamine and cocaine produce little or no physical dependence.

Treatment
Treatment for drug dependence depends upon the drug being withdrawn and often includes administration of another drug, especially for substances that can be dangerous when abruptly discontinued. Alcohol, benzodiazepines, and barbiturates are the only commonly abused substances that can be fatal in withdrawal. Increased heart rate and/or blood pressure, sweating, and tremors are common signs of withdrawal; confusion, seizures, and visual hallucinations indicate a serious emergency and the need for immediate medical care. Treatment usually requires the initiation and then tapering of a medication that has a similar action in the brain but a longer half-life. Though quite unpleasant and potentially dramatic, withdrawal from opiates is safe without medical intervention.