Drugs of abuse 3: alcohol Flashcards
What defines binge drinking?
more than 8 units in one sitting
What defines a unit?
- 10ml or 8g of absolute alcohol
Where is alcohol absorbed from?
- the stomach 20%
- the gut 80%
What is the speed of onset proportional to?
- the speed of gastric emptying
if your stomach is full then gastric emptying is reduced as the stomach metabolises and breaks up your food- the alcohol remains in the stomach for a lot longer rather than moving to the small intestine where it is absorbed
Where is alcohol mainly metabolised, by what enzymes and what into?
- the liver (85%)
alcohol dehydrogenase (75%) mixed function oxidase (25%)
into acetaldehyde
What happens if you drink alcohol in one large dose?
- if you have too much all the metabolising enzymes will become saturated and the level of blood ethanol will rise
How much of the alcohol is metabolised by the stomach?
15%
by alcohol dehydrogenase into acetaldehyde
What is the difference between body water in men and women and how does this effect alcohol distribution?
Women: 50% Men:59%
Alcohol is very soluble in water s the more body water the more dilute the alcohol will be in plasma
Women also have less alcohol dehydrogenase in their stomach compared to men
This all means that the plasma alcohol concentration will be higher in women compared to men
How and why is acetaldehyde in the body broken down?
- it is a very toxic metabolite
aldehyde dehydrogenase converts acetaldehyde into acetic acid
What is disulfiram?
it is used in alcohol aversion therapy and blocks the action of aldehyde dehydrogenase. This leads to a build up of acetaldehyde in the body, making the person feel worse after drinking and less likely to drink again due to this feeling.
What will a genetic polymorphism in aldehyde dehydrogenase lead to?
you will not be good at metabolising acetaldehyde and as it is a vasodilator this will lead to Asian flush
Why is it important that alcohol has low pharmacological potency?
you need a lot more alcohol compared to other drugs such as nicotine to get a response
What determines the effect of alcohol at a low dose?
- CNS agitation occurs but the effect it has depends on the environment and personality of the person
- in a social setting this can lead to excitability
What is the primary effect of alcohol and in a high dose?
it acts as a DEPRESSANT
What are the three main CNS targets of alcohol?
- GABA receptors
- NMDA receptors
- calcium channels
How does alcohol enhance GABA function?
it has both pre and post synaptic effect
- increases allopregnanolone production which then facilitates chloride channel opening
- this increase in chloride influx leads to a depressive effect
What impact does alcohol have on NMDA receptors and Ca+ channels?
- decreases NMDA receptor function
- negative impact on calcium channels, decreases calcium influx
How does alcohol create euphoric effects?
- enhances GABA
- switches off NMDA
Why does alcohol cause flushing?
- vasodilation
- reduced calcium entry and increased prostaglandins
Why does alcohol lead to an increase in HR?
-centrally mediated decrease in baroreceptor sensitivity which leads to an acute INCREASE in HR
decreasing baroreceptor firing rate leads to reduced parasympathetic stimulation which increases HR
What heart condition can chronic alcohol abuse be associated with?
-increased blood pressure
What is alcohols effect on urine outflow?
- it is a powerful diuretic
- this diuretic effect is caused by acetaldehyde
- it acts on the neurohypophysis and inhibits vasopressin release
What CNS disease is associated with chronic alcohol use? What does it cause to happen
- dementia
- cortical atrophy and a decrease in the volume of white matter
What causes wernike-Korsakoff syndrome?
thiamine deficiency
