What type of kinetics applies for alcohol in the body? Also, explain the clinical significance thereof.

Zero-order kinetics applies for alcohol.

There is a limited amount of NAD co-enzyme in the body. This cause a saturated enzyme system. This will lead to toxic side effects.

Give a brief summary of the metabolic pathways of ethanol metabolism.

Metabolism of alcohol (ethanol) follows two enzyme systems:

1. Alcohol dehydrogenase

2. MEOS (mixed function oxidases)

1. Alcohol dehydrogenase is the system that takes place during low to moderate consumption of alcohol. This is a zero-order kinetic system which means that a constant amount of alcohol is eliminated per unit time.

2. MEOS is the enzyme system that occurs during higher concentrations of alcohol consumption. This is usually concentrations above 100mg/dL. MEOS activity increases with chronic use and can be induced. This is partially responsible for tolerance.

The end product of these systems is acetaldehyde. 

Acetaldehyde is then further metabolized to acetate by the enzyme, aldehyddehidrogenase. Acetate is then converted to water and carbondioxide which is then eliminated.

Which drugs can affect this metabolism and what are the effects thereof?

Drugs that affect this metabolism include:

• Disulfiram
• Metronidazole
• Cephalosporins
• Hypoglycemics

These drugs inhibit or block aldehyddehidrogenase enzyme which then result that acetaldehyde cannot be converted to acetate. Buildup of acetaldehyde then occurs. This causes nausea, vomiting, etc. 

Sources

Brand, L. 2021. Alcohols. Study unit 3 [PowerPoint Presentation]. Unpublished lecture notes on eFundi, FKLG312. Potchefstroom: NWU.