What Is Drug Tolerance?

Drug tolerance occurs when a person’s reaction to a drug decreases so they need larger and larger doses to have the same effect. For example, if a person uses painkillers over an extended period of time, then they will need to consume larger and larger quantities in order to get the same results. Drug tolerance, in other words, is desensitization to a drug.

How Tolerance Develops

There are several different ways drug tolerance can develop. One way is called physiological tolerance. It occurs when the rate at which the drug is broken down, or metabolized, within the body increases. For instance, in the case of alcohol, the liver actually boosts the rate of production of various enzymes, which then accelerates the metabolism of the alcohol. Physiological tolerance can also occur when there is a decrease in the number of cell receptors the drug attaches to and the strength of those bonds weakens.

Another way tolerance can occur is through learned, or behavioral, tolerance. Learned tolerance develops through a learning process that involves recognizing the environment. When a person consumes a drug in the same setting over and over again, they will be less likely to feel the drug’s full effects as long as they are in that setting. However, if that same person took the same amount of a drug in an unfamiliar setting, then they will most likely feel stronger effects from the drug. Simply put, environment has an impact on drug tolerance.

Developing tolerance can become an issue for patients taking prescribed medications because it reduces the effectiveness of the drug. However, for addicts, drug tolerance can be especially dangerous because they will take larger and larger doses to get the same effects, potentially leading to an overdose.