The form of drug tolerance that arises when repeated exposure to the drug causes the metabolic machinery of the body to become more efficient at clearing the drug.

Metabolic tolerance

Decreased responding to a drug after repeated exposures, generally as a consequence of up- or down- regulation of receptors. 

Functional tolerance

A condition in which the development of tolerance for one drug causes and individual to develop tolerance for another drug. 

Cross tolerance

An uncomfortable symptom that arises when a person stops taking a drug that he or she has used frequently, especially at high doses.

Withdrawal symptoms

A process in which the body shows an enhanced response to a given drug after repeated doses

Drug sensitization

As a result of drug tolerance, some users of amphetamine would take large doses to experience a "high". From this, these users would develop symptoms of paranoia (auditory hallucinations, bizarre motor behavior, etc), which closely resembled schizophrenic symptoms.

Not only that, but amphetamine worsens symptoms of schizophrenia. Amphetamine is found to promote the release of dopamine and prolong the action of the released transmitter by blocking reuptake.

Drug Abuse as Support of the Dopamine Hypothesis of Antipsychotic Drugs

The body learns to rapidly down-regulate the function of a specific neurotransmitter when environmental cues for the drug are present. This decreases the effect of the drug on the body. Overdoses are more likely to occur when environmental cues are not present, since body does not down-regulate the receptors for this drug. 

Behavioral Tolerance/ Environment Dependent Tolerance

A condition in which, with repeated exposure to a drug, an individual becomes less responsive to a constant dose. 
 
- Metabolic tolerance 
- Functional tolerance 
- Behavioral Tolerance
- Cross-tolerance 
- Withdrawal symptoms
- Sensitization 


Bowdoin College

University of Michigan - Ann Arbor

Drug Effects 

Breedlove, S. & Watson, N. (2017). Behavioral neuroscience, eighth edition. Oxford University Press.

Behavioral Neuroscience 8th Edition

Lopez-Duran, N.L. (2021) Abnormal Psychology. Great River Learning Press.

Abnormal Psychology textbook

Drug tolerance

The amount of drug that reaches the brain and the speed with which is starts acting are determined in part by the drug's route of administration. 
- bioavailable
- biotransformation
- pharmacokinetics
- blood brain barrier

Drugs are administered and eliminated in many different ways

May result from single-agent drugs but are more likely to occur when multiple agents that have side effects/risk are administered together 

Drug-Induced Neurologic Conditions 


Some major categories of psychoactive drugs impact and affect behavior: 
- antipsychotics relieve schizophrenia
- antidepressants reduce chronic mood problems
- anxiolytics combat anxiety
- opiates relieve pain

Neuroactive drugs used to ease the symptoms of injury or psychiatric illness

Some of the major classes of neuroactive drugs that modify consciousness include: 
- cannabinoids 
- stimulants
- hallucinogenics 

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