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What Is Drug Tolerance?

Drug tolerance is a mental health condition that could have adverse health effects. Read on to learn about drug tolerance and its risk factors.

What is Tolerance?

Drug tolerance, otherwise called drug insensitivity, can be defined as a pharmacological term that describes the reduction in reaction to a drug after repeated intake. Drug tolerance is a reduction in an individual’s sensitivity to a particular medication that occurs because of repeated drug use by the person, usually to elicit an effect similar to when the individual first took it. 1

There are different mechanisms of drug tolerance, and these mechanisms may include behavioral effects, changes in the metabolism of a drug, and cellular changes. Tolerance is commonly viewed in a “negative” light; however, it is not always a bad thing.; for example, people may develop tolerance to the side effects of the drug over time. Reverse tolerance, a situation where sensitivity to a drug increases rather than decreases with subsequent doses, can also occur. Reverse tolerance drugs can include amphetamines or cocaine. 2

How Does Drug Tolerance Develop?

Tolerance to a drug develops when there's prolonged, repetitive drug use. This often occurs due to the brain and the entire body “adjusting” to the presence of the drug or substance of abuse. For example, when a substance like alcohol or morphine is taken for an extended period, larger doses are often required to elicit the same effect.

Prolonged drug use and the body’s adjustment results in an increase in drug metabolism levels. This is because the liver enzyme responsible for metabolizing drugs becomes more active. Tolerance also occurs because the bond’s strength between the cell receptors and the drug declines. 3

How Does Drug Tolerance Affect The Brain?

The mechanism of drug tolerance and its effects on the proper functioning of the brain is still not entirely understood. This is due to several different factors, one of which is that drug tolerance develops via different mechanisms. Nevertheless, tolerance to a drug may alter the brain’s communication system and interfere with the proper exchange and transmission of information from the brain to the body and vice versa. This is because it disrupts the normal functioning and activity of nerve cells in the brain. 4

What Is The Difference Between Tolerance, Dependence, and Addiction?

drug tolerance

Tolerance, dependence, and addiction are all terms commonly used together and in relation to each other. As a result, many people often misunderstand these terms, easily mistaking one for the other. However similar these terms might appear, they all have very distinct, very different meanings; that is, there is a difference between tolerance and dependence and addiction.

Drug Dependence

Drug dependence (also known as substance dependence) is a medical condition that occurs because of long-term drug usage. When there is prolonged brain exposure to drugs and substances with central activity, there is a change in the structure and function of the brain. As a result, the brain’s ability to function and operate becomes increasingly reliant on the presence of these drugs. 5

Drug Addiction

Drug addiction is a medical health disease characterized by compulsive drug use, even in adverse health effects arising from drug use. This is basically when a person cannot stop taking or “using” even when they begin to experience severe drug use-related health effects. 5

Tolerance vs. Dependence vs. Addiction

A person can be dependent on a drug without being addicted to it. It is also possible for an individual to have drug addiction without dependence on the drug. The easiest way to differentiate between addiction and dependence is to see dependence as a step forward from addiction. Therefore, the symptoms of dependence usually include some or all of drug addiction. 5

Tolerance in drug addiction (also called conditioned tolerance), on the other hand, is reduced body responsiveness to the effects of a particular drug or substance. It should be said that although these conditions can present separately, they often occur in most drug abuse cases.

Drug Tolerance and Drug Abuse Cycle

Drug tolerance, drug abuse, and drug addiction sometimes occur together. These cases usually involve a sort of “cycle” where a preceding condition eventually gives rise to the next one. This is known as the drug tolerance and drug abuse cycle.

A drug tolerance and drug abuse cycle would look like an individual taking a particular drug or substance of abuse and getting a “high” or euphoric feeling. The individual then continues to take the drug to get that same effect; however, he discovers that he keeps needing more and more to achieve the effects he wants (drug tolerance). Suddenly, he realizes that he can’t stop using the drug even when he begins to experience some side effects, he uses it (drug addiction). Finally, it gets to the stage where the individual cannot afford to go without using the drug because without it, he cannot think or act appropriately (drug dependence).

Physical and Psychological Dependence

This drug dependence can be divided into physical dependence and psychological dependence. When drug withdrawal is initiated, physical and psychological dependence may manifest several mild to severe health conditions. Generally, the severity and duration of drug withdrawal symptoms felt or experienced usually depend on several factors such as how long the drug has been abused, the substance of abuse, and body physiology. 6 Some drug withdrawal effects include nausea, vomiting, hallucinations, delirium, and even seizures. 7

What Are The Risks Of Drug Tolerance?

When tolerance to a drug occurs in isolation, there is always the “temptation” to dismiss it as insignificant or of low consequence. Many people often feel like they can find another drug if they stop getting the effects they desire from a particular drug type. However, contrary to that belief, drug tolerance can be very dangerous.

What Is Dangerous About Drug Tolerance?

The dangers of drug tolerance depend on the type of drug consumed frequently. Drug tolerance can lead to a myriad of adverse effects, some of which include. 8


Drug tolerance can lead to addiction to the drug. For instance, when you consume a large dose of a drug for an extended period, there is a high chance you’ll end up addicted to that drug.8


Cross-tolerance refers to medical situations where an individual displays tolerance to a particular kind of drug despite having never used it before. This condition usually occurs when you develop tolerance to a drug similar in chemical structure, which is very common with antibiotics. Alcohol has also been observed to cause cross-tolerance to drugs like diazepam. 8


Drug tolerance significantly increases the risk of a drug overdose. This is because tolerance “encourages” consistent intake of larger and larger doses of a particular substance of abuse, which could easily result in a drug overdose condition. 8

Physical or Psychological Dependence

There is also a high chance that drug tolerance will result in drug dependence (physical and psychological dependence). Physical dependence is associated with tolerance to a drug and withdrawal symptoms unrelated to emotions, while psychological dependence is attached to cognitive and emotional symptoms.

Can External Factors Influence Drug Tolerance?

It is also quite possible for drug tolerance psychology levels of an individual to be influenced by certain external factors. These factors include:

  • Stress
  • Illness
  • The type of drugs
  • Purity of the drug
  • Age
  • Bodyweight
  • Method of administration
Drug Tolerance

Signs and Symptoms Of Drug Tolerance 

There are several signs and symptoms of drug tolerance. It is important that you recognize these drug tolerance psychology signs and symptoms so you will be able to quickly get appropriate help if you notice any of these signs. They include:

  • Anxiety
  • Consuming large quantity of drugs
  • Irritability
  • Nausea
  • Depressed mood
  • Aggression
  • Decreased appetite
  • Drug cravings

Find Help At Genesis Recovery

Although drug tolerance can be quite challenging to deal with, nevertheless if detected early enough, it can be effectively dealt with. Have you observed any symptoms of drug tolerance in yourself, or do you currently struggle with drug addiction? If you have, you need to get help at a treatment and recovery center right away! At Genesis Recovery, you will have access to all the help you need to take care of drug addiction and drug tolerance effectively.  

Our Programs

We understand that every patient is different, and so we offer individualized treatment programs designed to meet your specific treatment needs. Our programs include but are not limited to:

Genesis Recovery also offers treatment options like medication-assisted treatment (MAT) and a 12-Step model to get you through recovery.

Contact us now, and let’s help you begin your recovery journey towards an addiction-free life!


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