Synonyms

Sensitization

Definition

An increase in drug effect upon continual exposure to a drug in the organism, which was previously exposed to the drug.

Introduction

Drug sensitization is a process frequently encountered in the literature of the field of addictions and pharmacology, and it is an essential process towards the understanding of drug action and use.

Drug Sensitization in Substance Abusers

With repeated drug administration, gradual and incremental neuroadaptations are produced that make animals hypersensitive to the specific drugs. Even though users or abusers will be keeping the same dosage levels, drug effects will be greater and greater, therefore they would become intoxicated even in small doses. Using repeatedly a drug but with some pauses in between causes greater sensitization compared to taking a single dosage or even taking repetitively the drug. Moreover, sensitization is promoted if periods of use are alternated with periods of abstinence. When a person who is sensitized let’s say to cocaine and abstains from use for some time, he/she is at risk of fatal overdosing at reuse (Steketee & Kalivas 2011; Robinson & Berridge 2008). Known addictive substances, that sensitization has been observed in, are cocaine, amphetamines, morphine, nicotine, and even alcohol; importantly, not all drugs subject to sensitization, mostly stimulants. In addition, the selected route of drug administration as sensitization is influenced by the speed or the time it takes for a drug to reach the brain. Sensitization in the case of drugs is long lasting with its effects on behavior and cognition lasting for years even with abstinence; however, factors such as the time lapse between dosages, the choice of drug, the age and sex of the user, and genetics influence the strength of sensitization. Due to these factors, vulnerability to sensitization differs between individuals Steketee & Kalivas (2011). That provides an insight into the long-asked question of why some users become addicts while others do not get addicted. The sensitization of behavior and other psychological or psychomotor functions implies neural sensitization. Drugs seem to alter or reorganize neural systems and neurotransmitters, and even though causal relationships are yet to be established, neuroadaptations seem permanent. The permanency of changes in neurotransmitter circuits have crucial implications on the matter of cravings and relapse. Of special importance is the sensitization of the mesolimbic pathway of the mesotelencephalic dopamine system. Since dopamine is responsible for the motivation to go after pleasure and happiness and fulfill our “wants,” drugs come to jeopardize this process by making dopamine hyperreactive, consequently increasing the prominence of drug cues, hence the intense cravings Robinson & Berridge (2008). The aforementioned comprise the “Incentive Sensitization” theory of addiction developed by Berridge and Robinson (1998) and is noteworthy of further reading.

Conclusion

Drug sensitization is a complex process influencing drug users in a cellular level and in consequence in a behavioral level.

Cross-References