Impaired absorption of paracetamol in vegetarians

Area of Science:

• Pharmacokinetics
• Nutritional Science
• Gastroenterology

Background:

• Dietary habits can influence drug absorption and disposition.
• Vegetarian diets exclude animal products, potentially altering gastrointestinal function and nutrient absorption.
• Paracetamol (acetaminophen) is a widely used analgesic and antipyretic, making its absorption profile clinically relevant.

Purpose of the Study:

• To investigate the impact of a vegetarian diet on the absorption and disposition of paracetamol.
• To compare pharmacokinetic parameters of paracetamol between healthy Thai vegetarians and non-vegetarians.

Main Methods:

• A comparative pharmacokinetic study involving 10 healthy male Thai vegetarians and 10 non-vegetarians.
• Oral administration of paracetamol at a dose of 20 mg/kg.
• Measurement of plasma paracetamol concentrations over time to determine key pharmacokinetic parameters (Cmax, tmax, AUC) and urinary excretion of paracetamol and its metabolites.

Main Results:

• Vegetarians exhibited significantly impaired paracetamol absorption, characterized by lower peak plasma concentration (Cmax) and delayed time to reach peak concentration (tmax).
• The time required for 50% of the total paracetamol dose to be absorbed was significantly longer in vegetarians.
• Total 24-hour urinary recovery of paracetamol and its metabolites was significantly lower in vegetarians, indicating reduced extent of absorption, although overall AUC did not differ significantly.

Conclusions:

• Vegetarian diets are associated with significantly impaired absorption rate and extent of paracetamol.
• Differences in absorption may be attributed to dietary influences on gastrointestinal physiology.
• Plasma paracetamol half-life and metabolic clearances were similar between groups, suggesting absorption, not elimination, is primarily affected.