Addictions Flashcards
What is tollerance?
- Defined as “Reduced responsiveness to a drug caused by previous administration”
- Develops in response to many types of drug
□ e.g. opioids, ethanol, barbiturates, benzodiazepines - An example of homeostasis
□ the body likes things the way they were
What are the mechanisms underlying tollerance?
□ Dispositional
® less drug reaches the active site, e.g.
◊ decreased rate of absorption
◊ increased rate of metabolism to inactive metabolites
◊ decreased rate of metabolism to active metabolites
◊ increased rate of excretion
□ Pharmacodynamic (aka tissue or functional tolerance)
® site of action is less affected by the drug, e.g.
◊ down-regulation or internalisation of drug receptors
◊ reduced signalling down stream of drug receptors
◊ some other compensatory mechanism
Why does the development of tellerance lead to withdrawal symptoms?
® e.g. a drug reduces a transmitter release
® The body adapts to this by increasing the sensitivity to the transmitter
® When the drug wears off the body is left with an increased sensitivity to the transmitter but regular transmitter release
What is the withdrawal phenomena?
□ Therefore the withdrawal effect of a drug is usually the reverse of the acute effect
□ Tolerance & dependence are closely linked
□ Development of tolerance may lead to physical dependence in order to avoid the (unwelcome) withdrawal effects
What is the reward pathway?
® Neurones project from the ventral tegmental area to the nucleus accumbens & prefrontal cortex
® When VTA neurones are stimulated they release dopamine
® This causes a sensation of pleasure/reward
Name some stimulants
- Cocaine
- Amphetamine
How is cocaine taken?
□ Coca leaves chewed or brewed
□ Cocaine hydrochloride is snorted or injected
□ Cocaine freebase or crack cocaine is smoked
What are the effects of cocaine?
□ stimulant and euphoriant ® increased alertness and energy ® increased confidence and impaired judgement ® lessens appetite and desire for sleep □ damage to nose and airways ® Tiny vessels in the nose become constricted and die □ convulsions with respiratory failure □ cardiac arrhythmia's and MI □ hypertension and CVA □ toxic confusion □ paranoid psychosis
How long does it take for cocaine to take affect?
□ depends on dose and rate of entry to the brain
® smoking - almost immediate
® injecting - 15 to 30 secs
® snorting - 3 to 5 mins
® the effects of crack smoking are very intense but quickly over (15 mins)
What are the withdrawal effects of cocaine?
□ Depression □ Irritability □ Agitation □ Craving □ Hyperphagia- abnormally great desire for food □ Hypersomnia
What are the effects of amphetamine?
- Effects similar to cocaine but longer lasting
- Toxic confusion occasionally with convulsions and death
- Amphetamine psychosis in heavy chronic use
Name some opiates
- Opium
- Morphine
- Heroin (diamorphine)
- Methadone
- Codeine and dihydrocodeine
How is heroin taken?
□ Snorting
□ Smoking (chasing the dragon)
□ Injection
□ Smoking is the safest, injection is the most dangerous method of use
What are the side effects of heroin?
□ Analgesia
□ Drowsiness and sleep
□ Mood change (euphoria, intense pleasure)
□ Respiratory depression
□ Cough reflex depression
□ Sensation of the labyrinth with nausea and vomiting
□ Decreased sympathetic outflow (bradycardia and hypotension)
□ Lowering of body temperature
□ Pupillary constriction
□ Constipation
□ Respiratory arrest with a pulse (almost pathogenic of opiate overdose)
□ Pinpoint pupils unreactive to light
□ Snoring giving way to shallow respiration (<8 breaths/min)
□ Varying degrees of reduced consciousness/ coma
What are the effects of opiates?
- Intense but transient feeling of pleasure
□ A rush
□ Almost orgasmic
□ Physical and emotional anaesthetic
