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Physiological vs. Psychological Drug Tolerance

Instructor: Adrianne Baron

Adrianne has a master's degree in cancer biology and has taught high school and college biology.

In this lesson, we are going to look at physiological as well as psychological drug tolerance. We will cover how these two types of drug tolerance develop and go over the similarities and differences.

Drug Tolerance

What do you anytime you are riddled with an ache or pain in your body? If you are like most people, you pop some type of pain pill in the hopes of it relieving the pain. You may be beginning to notice, however, that you are not just popping one pill anymore. You find yourself popping multiples of that same one pill that used to take care of your pain completely.

Drug tolerance leads to taking more pills
Picture of pills

What you are experiencing is called drug tolerance. This means that a drug is becoming less effective in your body so it takes a larger amount of the drug in order for it to cause the same effect it normally would. You were taking the medicine as directed, so you are probably wondering how this happened? It may have happened for one of two reasons or due to both reasons working together.

Physiological Drug Tolerance

One type of drug tolerance is physiological drug tolerance, which is when your body needs more of the drug in order to respond to the drug. There are two mechanisms for how this happens. The first way is that your body becomes less sensitive to the drug. Taking the drug regularly over an extended period of time causes your body to become used to the drug being in your body. This leads to a decrease in sensitivity leading to the need for more of the drug to be in your body at the same time for your body to give the desired response to the drug.

The other way physiological drug tolerance develops is that the full amount of the drug does not make it to the desired target in the body. This may happen as a result of the drug being absorbed in other parts of the body rather than making it to the designated target site for the drug. When this begins to occur, more of the drug has to be taken in order to get the amount that reaches the target site to be the amount needed to get the desired response.

Psychological Drug Tolerance

The other type of drug tolerance is psychological drug tolerance, which is when it takes more and more of a drug in order to feel the mental rewards of a drug. Most drugs have some type of effect on the brain, especially the pain medicines. Dopamine, the feel-good chemical in the brain, is released when we take pain medications.

A certain amount of time after taking a drug, proteins are released in the brain that stop the release of dopamine. This causes you to feel like the drug has worn off, and then you need to take the drug again. The more and more you do this, the more you will realize that the time it takes for the drug to 'wear off' becomes shorter and shorter. So, you take more of the drug to get the desired effect.

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