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

• Alcohol follows zero-order kinetics, meaning that the same amount of alcohol is metabolized at a time even if the concentration of alcohol in the body increases (7-10g/h). This leads to intoxication as the body ends up with more alcohol than it can metabolize.

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

• Ethanol metabolism follows two enzyme systems, the alcohol dehydrogenase system and the microsomal ethanol-Oxidizing system (MEOS).
• Alcohol dehydrogenase are cytosolic NAD dependent enzymes, that metabolize low to moderate amounts of alcohol. This is due to the fact that there is a limited supply of the NAD coenzyme, the reaction follows zero order kinetics.
• The MEOS kicks in at blood ethanol levels higher than 100mg/dL, an  increase in MEOS activity with chronic use can be induced. This is partially responsible for tolerance.
• The end product of both systems is acetaldehyde.

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

• Aldehyde dehydrogenase inhibitors such as disulfiram. metronidazole, hyperglycemic drugs and cephalosporines effect this metabolism, they prevent acetaldehyde from being metabolized to acetate by aldehyde dehydrogenase. This causes a nausea and flushing reaction in individuals even with small amounts of alcohol absorption, due to the accumulation of acetaldehyde.