Pharmaceutical Research

, Volume 16, Issue 4, pp 478–485

Grapefruit Juice Activates P-Glycoprotein-Mediated Drug Transport

  • Andrea Soldner
  • Uwe Christians
  • Miki Susanto
  • Vincent J. Wacher
  • Jeffrey A. Silverman
  • Leslie Z. Benet
Article

Abstract

Purpose. Grapefruit juice (GJ) is known to increase the oral bioavailability of many CYP3A-substrates by inhibiting intestinal phase-I metabolism. However, the magnitude of AUC increase is often insignificant and highly variable. Since we earlier suggested that CYP3A and P-glycoprotein (P-gp) form a concerted barrier to drug absorption, we investigated the role of P-gp in GJ-drug interactions.

Methods. The transcellular bidirectional flux of drugs that are (i) CYP3A-and/or P-gp substrates (Vinblastine, Cyclosporine, Digoxin, Fexofenadine, Losartan) or that are (ii) primary CYP3A-substrates (Felodipine, Nifedipine) was evaluated across MDCK-MDR1 cell monolayers with or without GJ, verifying monolayer integrity at all times.

Results. While both apical-to-basal (A-B) and basal-to-apical (B-A) fluxes of all CYP3A/P-gp substrates tested were increased in the presence of GJ, the resulting net efflux (B-A/A-B) was in all cases significantly greater with GJ than control (Vin, 28.0 vs. 5.1; CsA, 9.9 vs. 2.8; Dig, 22. 9 vs. 14.7, Fex, 22.3 vs. 11.1, Los, 39.6 vs. 26). In contrast, no such GJ flux effect was observed with Pel and Nif, substrates of CYP3A only (2 vs. 1.7 and 1.2 vs. 1.3).

Conclusions. GJ significantly activates P-gp-mediated efflux of drugs that are substrates of P-gp, potentially partially counteracting the CYP3A-inhibitory effects of GJ.

grapefruit juice bioavailability active transport intestine cytochrome P450 3A metabolism 

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Copyright information

© Plenum Publishing Corporation 1999

Authors and Affiliations

  • Andrea Soldner
    • 1
  • Uwe Christians
    • 1
  • Miki Susanto
    • 1
  • Vincent J. Wacher
    • 2
  • Jeffrey A. Silverman
    • 2
  • Leslie Z. Benet
    • 1
  1. 1.Department of Biopharmaceutical Sciences, School of PharmacyUniversity of CaliforniaSan Francisco
  2. 2.AvMax Inc.Berkeley

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