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

Ethanol gets eliminated from the body through zero-order kinetics. This means that no matter what the BAC is, and even when the amount of alcohol intake increases, the elimination rate stays the same. 

This means that if a person drinks a lot of alcohol rapidly, the ethanol will accumulate in the body and exaggerate the effects thereof. 

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

Alcohol is metabolized mostly in the liver by 2 pathways/systems, namely Alcohol dehydrogenase system and Microsomal Ethanol-Oxidizing system. 

Alcohol dehydrogenase: is used when there is low to moderate amounts of ethanol in a person’s blood. Alcohol dehydrogenases convert the ethanol to acetaldehyde by means of the NAD+ coenzyme. There are limited NAD+ enzymes and they may become saturated. 

Acetaldehyde is a highly toxic substance and known carcinogen, which is further metabolized into a less active metabolite, acetate.

Microsomal Ethanol-Oxidizing system (MEOS): is used when there are higher concentrations of ethanol in a person’s blood. Here, mixed function oxidases convert ethanol into acetaldehyde when it binds to the binding site of CYP2E1. The acetaldehyde is then converted to acetate. This system only kicks in when a person has had large amounts of alcohol and is increased with the chronic use of alcohol and increases a person’s tolerance to ethanol.

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

• Disulfiram
• Metronidazole
• Cephalosporins
• Hypoglycaemics 

These drugs block the effects of acetaldehyde dehydrogenase which results in the accumulation of acetaldehyde, causing an unpleasant reaction. These reactions include:

• facial flushing,
• nausea,
• vomiting,
• dizziness, 
• headaches, etc. 

These drugs are used to deter alcoholics from drinking.