What is Drug Tolerance?


By David Joel Miller, MS, Licensed Therapist & Licensed Counselor.

Drugs.

Drugs.
Photo courtesy of Pixabay.

What does it mean to develop drug tolerance?

The term tolerance or to develop tolerance has been a common concept in substance use disorder treatment for a long time. Tolerance has one meaning in that context but can have a number of other meanings in the field of medicine or pharmacology. None of these types of tolerance have anything to do with the idea of acceptance of diversity the way the word tolerance is used in political or social contexts.

Tolerance in Drug Treatment.

In Alcohol and Drug Counseling and CD (Chemical Dependency), thinking Tolerance is one of the first signs that someone’s body is being altered by the use of chemicals. Tolerance for drugs, and in this context Alcohol is a drug, means needing more of a drug to get the same effect or getting a smaller effect if you use the same amount you had been using.

Tolerance, along with Withdrawal symptoms have long been the hallmarks of addiction. Recently, in recognition that people can and do develop tolerance for prescribed drugs, even those with low abuse potential, we have also begun adding the concept of cravings to the characteristics of a substance use disorder.

A simple example of tolerance to alcohol.

When someone first starts drinking one or two beers may have a significant effect on them. After years of practice, that person may need to drink 6 or even 12 beers a night to get the same buzz. Someone who drinks a lot and develops substantial tolerance may be able to talk coherently or even act “sober” after substantial consumption of alcohol. They may think they have learned to “handle their liquor.”

Despite developing this tolerance if we were to put that person on a driving simulator they would fail the test. They may be able to make some compensations in their behavior to fool themselves and others but their brain’s reaction times and coordination are not fooled.

Drugs of abuse are not the only ones that build tolerance.

Many prescribed drugs need to be started at low doses until the body or brain “adjusts” to the new medication. Even drugs with little or no abuse potential still develop tolerance. As time passes that person’s dose will need to be increased because tolerance has developed.

One aspect of tolerance is that you might develop a tolerance to the side effects of a drug over time while not developing a tolerance to the medicinal effects. This explains the need to sometimes gradually increase the dose of these drugs until the level in the body reaches a “therapeutic level.”

Technically there are multiple types of tolerance.

In pharmacology texts or AOD counseling books with sections on pharmacology, they describe three types of tolerance. These are sometimes subdivided. In substance abuse counseling we also talk about “selective tolerance” the concept that it may be possible for the body to develop tolerance for some effects of a drug but not others. Personally, I think of “tolerance” as the body’s natural adaption to the presence of a specific chemical. Sometimes that developing tolerance can be beneficial and sometimes it is harmful.

Tolerance can develop slowly to some drugs and rapidly for others. For example tolerance to many hallucinogens develops from a single dose. Try to use that drug again tomorrow and it will have little or no effect.

Functional Tolerance involves changes in the body’s behavior.

Functional tolerance can be further subdivided into Acute and Protracted Tolerance. Acute involves changes to the body’s reaction to that one first dose of drugs over the time that dose is in the body. Protracted tolerance is a change in the results from the second or third dose on the same using occasion.

Acute Tolerance develops during a single use of a drug.

In Acute tolerance, the body responds more significantly as the level in the blood is rising. As long as it keeps going up the effect is maintained. Once the blood level drops the adverse effects kick in. With alcohol as long as the level in the blood is rising the hangover is held at bay. Regardless of how high the level, once it starts to drop, the withdrawal effect, the hangover with alcohol, kicks in.

Protracted Tolerance

The second type of functional tolerance called protracted tolerance is best demonstrated by stimulant drugs like cocaine. The first dose produces a strong effect but after that first dose, each subsequent one produces less and less of an effect.

Metabolic or Dispositional Tolerance is how long the drug lasts.

How rapidly the drug is metabolized and eliminated changes over time and also varies from drug to drug.  For many, but not all drugs, the more you take or do the faster your body metabolizes and eliminates that drug. Some drugs, LSD for example, develop metabolic tolerance very rapidly.  Other drugs like Alcohol maintain a pretty constant rate of metabolism while the tissues and nerves alter their response.

Behavioral or Learned Tolerance.

People who frequently consume alcohol learn to slow down their walk and alter their stance to hide that they are under the influence. Many other adaptions of behavior to compensate for frequently having a particular drug in your system are possible.

Selective Tolerance.

When you develop tolerance to some of a drug’s effects but not others this is called selective tolerance. Heavy coffee drinkers find it stimulating in the morning but may develop a tolerance to caffeine’s sleep preventing effects.

Reverse Tolerance.

This form of tolerance involves becoming sensitized to a particular drug or substance so each time you take that drug there is a stronger effect than the previous time.

Cross-Tolerance.

Cross-tolerance is when someone who has been using a particular drug will develop a tolerance to other similar drugs. Someone who drinks alcohol will develop a tolerance to Barbiturates or surgical anesthetics even though they have never had those drugs in the past.

Terms and their meaning can differ with the profession using them. The literature from the Rehab or AOD (Alcohol and Other Drug) field may be very different from that in the mental health field. There is still a large gap between recovery programs and AOD professionals and the terms and descriptions used in the DSM.

Related posts: Drug Use, Abuse, and Addiction      Recovery

More “What is” posts will be found at “What is.”

FYI These “What is” sometimes “What are” posts are my efforts to explain terms commonly used in Mental Health, Clinical Counseling, Substance Use Disorder Counseling, Psychology, Life Coaching, and related disciplines in a plain language way. Many are based on the new DSM-5; some of the older posts were based on the DSM-IV-TR, both published by the APA. For the more technical versions please consult the DSM or other appropriate references.

Staying connected with David Joel Miller

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2 thoughts on “What is Drug Tolerance?

  1. Pingback: Why do drugs affect people differently? | counselorssoapbox

  2. Pingback: What is an Alcohol Use Disorder? | counselorssoapbox

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