Pharmaceutical Research

, Volume 15, Issue 3, pp 423–428

Active Apical Secretory Efflux of the HIV Protease Inhibitors Saquinavir and Ritonavir in Caco-2 Cell Monolayers


DOI: 10.1023/A:1011924314899

Cite this article as:
Alsenz, J., Steffen, H. & Alex, R. Pharm Res (1998) 15: 423. doi:10.1023/A:1011924314899


Purpose. To investigate in vitro the mechanisms involved in the gastrointestinal absorption of the HIV protease inhibitor, saquinavir mesylate (Invirase®), whose oral bioavailability is low, variable, and significantly increased by co-administration with ritonavir, also an HIV protease inhibitor but with higher oral bioavailability.

Methods. Confluent epithelial layers of human Caco-2 cells mimicking the intestinal barrier.

Results. Both saquinavir and ritonavir showed polarized transport through Caco-2 cell monolayers in the basolateral to apical direction (secretory pathway), exceeding apical to basolateral transport (absorptive pathway) by factors of 50-70 and 15-25, respectively. Active efflux was temperature dependent, saturable and inhibited by verapamil and cyclosporin A. Saquinavir and ritonavir decreased each other's secretory permeability and hence elevated their net transport by the absorptive pathway.

Conclusions. Saquinavir and ritonavir are both substrates for an efflux mechanism in the gut, most likely P-glycoprotein, which acts as a counter-transporter for both drugs. Together with sensitivity to gut-wall metabolism by cytochrome P-450 3A, this may partially account for the low and variable oral bioavailability of saquinavir in clinical studies and for its increased bioavailability after co-administration with ritonavir.

HIV protease inhibitors saquinavir ritonavir Caco-2 cells efflux system 

Copyright information

© Plenum Publishing Corporation 1998

Authors and Affiliations

  1. 1.Preclinical Research Department, Pharma DivisionF. Hoffmann-La Roche Ltd, GrenzacherstrasseBaselSwitzerland
  2. 2.F. Hoffmann-La Roche Ltd., GrenzacherstrasseBaselSwitzerland

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