Flashcards in Pharmacokinetics In Practice lecture Deck (10):
Why is ethanol the perfect drug?
1. Soluble in water- in order to absorb
2. Not charged- can pass through membranes
3. Small molecule
4. Not subject to changes in molecular structure as a result of changes in the acidity (pH)
5. Soluble in fatty substances (lipids)
- Can pass through the lipid membrane barriers in the body
(stomach into the blood or from intestines into the blood) (readily absorbable)
Calculate the molar concentration of alcohol in the blood for the UK drive limit
C. 80mg/100ml for england
B. 50mg/100ml for scotland
Use Mass = moles x concentration
46.07g per 1litre per 1M concentration
80mg per 100ml per 0.0176M
What are the factors that may effect absorption when it comes to ethanol?
1. Rate of consumption
2. Volume consumed
3. Concentration of ethanol in the drink (strength, different %)
4. Presence or absence of carbonation (e.g. carbonation increases rate of absorption like in champagne there's bubbles)
5. The presence or absence of food in the stomach (food delays absorption)
6. Taking any medications that can interfere with GI motility
Calculate the volume of distribution in an average man 70kg man?
Total body H2O?
1. H2O= 0.6 x 70 = 42 Litres (Large Vd)
2. Extracellular (1/3)= 14 litres
3. Intracellular (2/3)= 28 litres
4. Interstitial fluid (11.2 litres)
5. As plasma is 2.8 litres (approximately 3 litres) (Small Vd)
What percentage of ethanol is metabolised in the liver?
Explain first order kinetics and zero order kinetics in relation to ethanol metabolism?
First order is where the actual plasma concentration dictates the rate of elimination: threshold is 10mg/dl (decilitre)
Enzymes can no longer work to eliminate amount of ethanol
Zero order kinetics there after
How is ethanol metabolised in the liver?
Ethanol is converted to Acetaldehyde which is converted to Acetate
1. Ethanol to Acetaldehyde
- NADPH => NADP
- NAD+ => NADH
2. Acetaldehyde to Acetate
- Disulfiram (Aldehyde dehydrogenase inhibitor)
- NAD+ to NADH
How is ethanol excreted in the liver? And how is it allowed to determine blood alcohol levels?
1. 5% is excreted unchanged
2. Allows for breathalysers to determine blood alcohol levels, everyones is different though. (Has to be absorbed into the blood stream though)
3. Ratio of 2100:1 of breath alcohol to blood alcohol
What are the classic symptoms that are linked to the consumption of ethanol and explain how they occur?
- GABA receptor increased inhibition
- Glycine receptors
2. Ataxia (random muscle movements
- Acetylcholine receptors
- Acetylcholine receptors on the gut