Drug Tolerance: The 7 Clinical Types

There are 7 types of tolerance to chemical substances, all of which have at least some impact on the processes of drug abuse and addiction. Tolerance invariably leads many addiction-prone people to use more and more of a substance in order to achieve the same results, but there's more to it than this alone. In fact, most people are unaware that there is more than one type of tolerance. The following are the 7 types and their descriptions.

Acute

Acute tolerance refers to a process whereby the brain and central nervous system enact processes to immediately mitigate the effects of a given substance. The most common substances used as examples of this are nicotine - which not only creates acute tolerance but in some cases may increase tolerance throughout the day for some smokers - and hallucinogens like psilocybin mushrooms, LSD, Ecstasy, Philosopher's Stones, Peyote and others.

Acute tolerance means that in most cases the effects of these drugs will be minimized by the reduction of receptor sites in the brain for each particular substance, and in some cases for certain classes of substances.

Behavioral

Experienced drug users demonstrate behavioral tolerance when they adjust their appearance, mannerisms and behavior in order to mask their drug use. Some chronic users are able to suddenly appear sober when presented with a stress such as authority, and then return to being "high" when the threat passes. This can also occur when a person who is high is subjected to a sudden and dramatic experience, where the brain will quickly refocus on the new threat and the high will diminish or be eliminated.

The human brain is a remarkable organ and is able to quickly adapt to many different chemicals. Acute tolerance allows the brain in part to use areas of the brain not affected by the substance in question, then revert to its normal state when the drug is not present, barring of course long-term changes related to chronic drug abuse and addiction.

Dispositional

Part of the problem with many drugs - including cocaine, meth and heroin, is that the brain cannot dispose of the drugs on its own. In most cases the brain relies on the interactions between neurotransmitters and receptors, but drugs interrupt this process, leaving the brain helpless to respond. Dispositional tolerance refers to the body essentially taking this task over by speeding up the metabolism so that the blood can circulate the foreign substances quickly for removal by the liver. This reduces the effect of the drug and in general means that in order to achieve the same effects, addicts will need to increase their doses.

Inverse

Inverse tolerance is not entirely understood, and in fact this type of tolerance has a dual-characteristic that makes it more challenging to analyze and comprehend. Inverse tolerance is effectively the same as the Kindling Effect, which refers to changes in the brain and central nervous system concerning the way chemicals are processed. The Kindling Effect refers to either a sensitization - such as chronic alcohol use and breakdown of the liver and thus the body's ability to "handle" alcohol - or desensitization, where the effects of a chemical become more pronounced.

Inverse tolerance can have a significant impact on subsequent relapses from recovery attempts, resulting in an increase in the severity and duration of symptoms related to withdrawal and post acute withdrawal.

Pharmacodynamic

This type of tolerance is the brain actively working to mitigate the effect of a foreign substance. Nerve cells, transmission processes, reuptake and receptor sites can be adjusted by the brain to become desensitized to the drugs, effectively producing an antidote to the substance or increasing the amount of receptor sites in order to diffuse the chemical across a wider spread of sites and thereby lessen its effects.

Reverse

Often grouped together with Inverse Tolerance and Kindling, reverse tolerance refers exclusively to the increased sensitivity one experiences toward a particular drug as a result of the breakdown of the body's ability to process the substance. Reverse tolerance usually occurs in chronic alcoholics whose livers have stopped functioning normally and thus permit alcohol to remain in the blood longer and in higher concentrations, resulting in a severe increased sensitivity to the substance.

Select

This type of tolerance is not well-understood, but refers to the fact that in some cases the brain will selectively mitigate some effects of a substance, but not others. For instance, some people may smoke marijuana for a long period of time without obtaining the "euphoric" effect, despite the fact that other parts of the body - especially the lungs, throat, and cannabinol receptors, are clearly being affected.

This could be dangerous in some cases where higher doses of a substance are taken in order to attempt to offset the select tolerance to a particular drug. For example, a person may not get the "high" they are seeking from heroin, despite the fact that the drug is having severe effects on other parts of the body. In order to get this high, the user may consume more than normal and in doing so poison their body without realizing it because they relate the potency, toxicity and effect of the drug to the high alone. This is a dangerous situation that could result in a fatal overdose.

The real issue with most types of tolerance is that is does not allow the body to function as it normally would, and invariably addicts consume more and more of a substance in an effort to offset the effects of tolerance. This is a dangerous cycle that must be arrested as quickly as possible. In fact, even people who are on legitimate pain medication, sleep medication or other legitimate prescriptions can fall victim to tolerance and the eventual dependency and outright addiction that comes shortly after with continued use. If this describes you or someone you love, you need to get help right now to correct this balance before it's too late.