Tolerance

What is tolerance?

When repeated doses of a drug are taken (prescribed or illicit) tolerance to the drug is likely to develop; i.e. the body learns to deal with the effects of the drug. Increasing tolerance results in a progressively decreasing drug effect, and the need for an increased dose; addiction and habituation being the final outcome. Thus addicts can tolerate, for example, doses of morphine that would be considered toxic or even fatal in a non-tolerant individual.

Given a blood-toxicity level, the degree of intoxication will be dependent on the individual's tolerance to a drug's effects acquired through regular consumption. As an example, regular, heavy drinkers (commonly termed as alcoholics) may be less susceptible to the effects as a higher concentration is necessary to produce alcohol intoxication compared to a naive drinker.