15. Alcohol Flashcards
how can the total amount of alcohol in a drink be proved?
absolute amount: %ABV (alcohol by volume) x 0.78 = grams of alcohol/100ml
units: %ABV x actual volume (ml)/1000
what volume does 1 unit of alcohol equal?
10ml of absolute alcohol
what is considered the safe levels of alcohol?
14 units or less/week
what is binge drinking defined as?
> 8 units in 1 sitting
how does drinking on a full stomach influence your blood alcohol level?
alcohol is mostly absorbed from the SI so drinking on an empty stomach is most effective because fluid stimulates gastric emptying whereas a full stomach delays gastric emptying
how is alcohol metabolised?
- 90% is metabolised, 85% metabolised in the liver
- 10% is excreted unchanged: through lungs (hence breath test)
- liver metabolises alcohol by alcohol dehydrogenase (75%) and mixed function oxidase (25%)
how do liver enzymes metabolise alcohol and what is the effect?
- enzymes convert alcohol –> acetaldehyde
acetaldehyde is a toxic product that we don’t want building up in the blood
what does alcohol tolerance come from?
upregulation of mixed function oxidase enzymes by the liver - drinking more alcohol gives the same effect
why is dosing of alcohol important?
saturation of the liver and first pass metabolism: flooding with alcohol means the liver enzymes can’t metabolise a lot of it and it goes straight to the blood
where does the remaining 15% of metabolism occur?
stomach - alcohol dehydrogenase, alcohol is absorbed across the stomach
females have a lot less so metabolism isn’t as effective
why is water solubility relevant in alcohol distribution?
- alcohol is very water soluble
- men have more body water than women so alcohol is more diluted in men
- there is a more powerful effect in women
what does aldehyde dehydrogenase do?
converts acetaldehyde –> acetic acid (inert)
occurs in liver and stomach
what does a genetic polymorphism in the aldehyde dehydrogenase enzyme result in?
- common in asian populations
- polymorphism results in ineffective metabolism of acetaldehyde –> build up –> toxicity (nausea)
what does disulfiram do?
blocks aldehyde dehydrogenase
often given to alcoholics in alcohol aversion therapy so that when they drink alcohol acetaldehyde builds up, putting them off
describe the potency of alcohol
- low pharmacological potency
- simple molecule
- fits in many targets but with weak effects
- have to drink a lot to get an effect
what are the acute effects of alcohol in the CNS?
- depressant effect
- CNS agitation depending on degree of CNS excitability –> environment (non-social setting/social setting) and personality
what does alcohol interact with and what are the effects of these interactions?
- acts on GABA receptors –> increases function (direct effect)
- acts pre-synaptically –> increases allopregnenolone –> allopregnenolone binds to GABA receptors (indirect effect)
- decreases NMDA receptor activation
- interferes with calcium channel opening
why is alcohol said to behave like heroin when inhaled/at high dose?
alcohol binds to the opioid receptors in the CNS
it switches off the GABA receptor via the opioid receptor –> increased firing rate of dopaminergic neurones
what areas of the brain does alcohol impact and what are the effects?
- corpus callosum: rules, logic, impulse, feelings
- hypothalamus: appetite, emotions, temperature, pain sensation
- reticular activating system: consciousness
- hippocampus: memory
- cerebellum: movement and coordination
- basal ganglia: time perception
what are the acute effects of alcohol in the CVS?
- redness (cutaneous vasodilation) –> due to increased acetaldehyde
- acetaldehyde interferes with smooth muscle function in the arterioles
- calcium entry is impaired and prostaglandins are promoted –> vasodilation
what is the effect of alcohol on HR?
causes tachycardia:
- alcohol depresses baroreceptors –> no stimulation of PNS + loss of inhibition of SNS
what are the acute effects of alcohol in the endocrine system?
- diuresis (polyuria) due to increased acetaldehyde
- acetaldehyde inhibits vasopressin production –> less AQPs in the collecting duct –> loss of fluid
- increases ACTH –> increases cortisol
- negative effect on testosterone
what are the chronic effects of alcohol on the CNS?
THIAMINE DEFICIENCY (thiamine is necessary for the production of ATP in brain regions of high metabolic demand) LEADS TO:
- dementia: cortical atrophy/decreased volume of cerebral white matter
- ataxia: cerebellar cortex degeneration
what is wernicke-korsakoff syndrome?
seen in chronic alcoholics due to thiamine deficiency
wernicke’s encephalopathy: confusion, oculomotor symptoms, gait (reversible)
korsakoff’s psychosis: memory deficits (irreversible)
