Dv: Define Tachyphylaxis, Tolerance, Addiction, Dependence & Idiosyncrasy
Tachyphylaxis
- A decreased response to a drug which develops over minutes-hrs
- ↑dose will not ↑response
- Usually due to 2nd msg depletion or receptor internalisation
- ie depletion of stored NA on repeated Ephedrine doses
Tolerance
- larger doses are required to produce the same pharmacological effect
- Occurs over days-weeks
Addiction
- continued compulsive use of drug despite adverse health or social consequences. Addiction is a neurobiological disease with genetic, psychosocial and environmental factors. Individual uses a drug (drug abuse) → not all these people will go on to have addiction. Characterised by behaviours: impaired control of drug use, compulsive use, continued use despite harm, craving
- Ie Few patients who use opioids for post op pain will desire drug on withdrawal
Dependence
- repetitive exposure to a drug → body adaption → when drug is no longer available → signs of withdrawal à this is known as Dependence
- Ie withdrawal of nitrate VDs → rebound HTN → physical dependence
Idiosyncrasy
- rare & unpredictable response, not dose related. Caused by genetic differences in drug metabolism or immunologic mechanisms
- ie G6PdH deficiency → hemolysis with oxidative stress (ingestion of Fava beans)