Drug Dependence Flashcards
How can drug dependence occur?
Initial use of a drug is usually for its desirable effects. This can lead to repetitive use, eventually leading to drug dependence.
What is drug dependence?
Drug dependence is a state resulting from the interaction between a drug and an organism characterised by the compulsion to take a drug on a continuous or periodic basis to experience its psychic effects and/or avoid the discomfort of its absence.
What are the two components that make up drug dependence?
Dependence is commonly regarded as having two components: psychological and physical.
What is psychological dependence?
Psychological dependence is a condition in which a drug produces a feeling of satisfaction and a psychic drive that requires administration of the drug to produce pleasure or avoid discomfort.
What preclinical tests show psychological dependence?
- Preference test where animals are observed for their choice or preference against plain water or drugged water.
- Self-administration - animals are trained to press a lever to obtain a dose of IV drug
What is the mechanism behind psychological dependence?
The psychological effects of drugs are understood to involve dopamine systems in the CNS that mediate reward and reinforcement and reside in the ventral tegmental area of the midbrain and run up to the cortex.
What is physical dependence?
Physical dependence, most commonly experienced by depressants, is an adaptive state that manifests itself by intense physical disturbance when the drug is discontinued. It is responsible for the withdrawal syndrome experienced after drug intake ceases abruptly.
What are the mechanisms behind physical dependence?
Thought to result from an adpation of the CNS to the altered environment due to chronic drug abuse.
In the case of depressant drugs the CNS is believed to establish a new homeostatic state by supersensitivity of the pathways involved, counteracting drug depression. Supersensitivity can result from receptor supersensitivity, unmasking of neuronal pathways, enzyme induction, nucleotide changes or coupling to receptor, membrane depolarisation. When the drugs is discontinued the depressive effect on the CNS is removed and withdrawal symptoms result from this supersensitivity.
How does this lead to persistent drug use?
The combination of the physical and/or psychological dependence mechanisms result in an individual feeling forced by their body to take drugs, therefore leading to persistent drug use.
