European Journal of Clinical Pharmacology

, Volume 8, Issue 5, pp 293–299 | Cite as

Mechanism of the inhibitory effect of PAS granules on the absorption of rifampicin: Adsorption of rifampicin by an excipient, bentonite

  • G. Boman
  • P. Lundgren
  • G. Stjernström


The bioavailability (plasma concentrations, AUC and urinary excretion) of an oral solution of rifampicin was investigated in six healthy volunteers. Simultaneous administration of PAS granules produced a significant decrease in the absorption of RMP, whereas Na-PAS tablets had no effect. This indicated that the dosage form of the granules and not PAS itself was responsible for the interaction, and that the dissolution of RMP was not involved. The interaction could be reproduced by giving dummy granules that contained the same excipients but no PAS. The disintegration and dissolution of PAS granulesin vitro correlated well with the disappearance of RMP from the solution. The major excipient of the granules, bentonite (a mineral closely related to kaolin), was found to adsorb rifampicin rapidly and strongly.

Key words

Rifampicin p-aminosalicylic acid bentonite drug interaction bioavailability drug adsorption 


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Copyright information

© Springer-Verlag 1975

Authors and Affiliations

  • G. Boman
    • 1
    • 3
  • P. Lundgren
    • 2
  • G. Stjernström
    • 2
  1. 1.Dept. of Thoracic Medicine, Karolinska Hospital, Dept. of Clinical Pharmacology, Huddinge HospitalKarolinska InstitutetStockholm
  2. 2.Dept. of Galenic PharmacyUniversity of UppsalaSweden
  3. 3.Thoraxmedicinska kliniken Karolinska sjukhusetStockholm 60Sweden

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