Effects of food type on the extent of drug-drug interactions between activated charcoal and phenobarbital in rats

Drug Metab Pharmacokinet. 2019 Aug;34(4):287-291. doi: 10.1016/j.dmpk.2019.05.002. Epub 2019 May 18.


Activated charcoal is known to decrease the intestinal absorption of co-administered drug by adsorption. The extent of this drug-drug interaction (DDI) is attenuated by food intake. The aim of this study was to quantitatively evaluate the effects of food type on the extent of DDI between phenobarbital and activated charcoal using a rat model. Phenobarbital was orally administered at a dose of 1.5 mg/kg with or without 33 mg/kg of activated charcoal under fasted or fed conditions, and the plasma concentration profile of phenobarbital was monitored. Several fed conditions, such as a standard breakfast, high-fat meal or enteral nutrient used in human studies, were examined. Under the fasted conditions, activated charcoal significantly decreased the area under the plasma concentration - time curve (AUC) of phenobarbital by 45.2%. When the standard breakfast or high-fat meal was fed, this DDI was reduced to 28.3 and 18.0%, respectively, as assessed by the reduction in the AUC. On the contrary, enteral nutrient did not significantly attenuate the DDI. In conclusion, the influence of food intake on the extent of DDI between phenobarbital and activated charcoal was found to differ among the types of food concomitantly ingested.

Keywords: Absorption; Activated charcoal; Adsorption; Drug-drug interaction; Enteral nutrient; Food type; High-fat meal; Phenobarbital; Standard breakfast.

MeSH terms

  • Administration, Oral
  • Animals
  • Biological Availability
  • Charcoal / administration & dosage
  • Charcoal / pharmacology*
  • Drug Interactions
  • Eating*
  • Food-Drug Interactions*
  • Male
  • Models, Animal
  • Phenobarbital / administration & dosage
  • Phenobarbital / pharmacology*
  • Rats
  • Rats, Sprague-Dawley
  • Viscosity


  • Charcoal
  • Phenobarbital