1 The University of Texas Health Science Center at San Antonio, Department of Medicine, Division of Infectious Diseases (7881), 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA; 2 Departamento de Microbiología, Facultad de Medicina, Universidad Autónoma de Nuevo León, Monterrey, N.L., Mexico
Received 19 February 2003; accepted 12 March 2003
![]() |
Abstract |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Keywords: voriconazole, mice, grapefruit juice
![]() |
Introduction |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
In prior studies, Sugar & Liu2 demonstrated that mice treated orally with grapefruit juice substituted for drinking water have detectable voriconazole up to 1.6 mg/L 4 h after an oral dose of 20 mg/kg/day. Furthermore, Sugar & Liu3 found that mice infected with Blastomyces dermatitidis responded clinically to treatment with voriconazole and grapefruit juice. Grapefruit juice contains naringin and 6',7'-dihydroxybergamottin, both of which inhibit gut mucosal cyp 3A4. This in turn raises blood levels of drugs normally metabolized by cyp 3A4.4,5 Therefore, we considered that grapefruit juice might inhibit voriconazole metabolism by the mucosal cytochrome enzymes and thus increase intestinal absorption and systemic delivery of voriconazole. Although this mechanism has not been demonstrated specifically for voriconazole, as per Sugar & Liu,2 grapefruit juice does cause a prolonged rise in voriconazole serum concentrations.
Fusariosis is an infection associated with severe immune suppression. Treatment is difficult, as the organisms are often resistant to amphotericin B.6 In vitro studies show that Fusarium isolates tend to be susceptible to voriconazole, genaconazole and fluconazole, but not itraconazole.7 Some responses to fluconazole have been noted in mice with fusariosis, and responses to voriconazole have been noted in humans infected with Fusarium (Pfizer company files). Accordingly, we considered that grapefruit juice treatment might slow the clearance of voriconazole sufficiently for the drug to be effective in murine fusariosis.
![]() |
Materials and methods |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
F. solani isolate 95-2478 was obtained from the Fungus Testing Laboratory, University of Texas Health Science Center, San Antonio. The MIC of voriconazole for F. solani was 2 mg/L at 48 h incubation.8 Fungi were grown on potato flake agar at room temperature until used. Fusarium mycelial colonies were harvested by scraping the plates with sterile isotonic saline and filtering the suspension through sterile glass wool to remove hyphal fragments. Conidia were counted in a haemocytometer and suspended at the desired concentration in isotonic saline. The inocula were prepared in volumes of 0.2 mL per mouse, and confirmed by serial colony count dilutions. The viable inoculum counts are reported.
Animals
Outbred ICR mice, weighing 2530 g, were housed four per cage and given food and water ad libitum. On the day before Fusarium infection, mice were given a single dose of 5-fluorouracil 150 mg/kg intravenously.
Treatment
Voriconazole (obtained from Pfizer) was dissolved in polyethylene glycol. Controls were given polyethylene glycol in 0.2 mL volume once daily and also grapefruit juice. Commercially obtained bottled grapefruit juice was administered by gavage at 0.2 or 0.5 mL once daily. Administration of grapefruit juice was started 3 days before the beginning of the voriconazole therapy, or on the day voriconazole therapy began, and was continued during voriconazole administration. Treatment with voriconazole, in a volume of 0.2 mL by gavage once daily, was started 1 day before or 1 day after infection. For survival studies, the regimen was continued for 10 days after infection. Survival was observed to day 15, by which time deaths had stopped. For tissue burden studies, mice were treated to day 7. One day later, tissues were removed aseptically, homogenized and plated for serial colony count dilutions. Effort was made to keep trauma to the tissue constant.
Statistics
The logrank test was used to compare survival between treated and control animals. The MannWhitney test was used for comparisons of tissue burden. P 0.05 determined significance.
![]() |
Results |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
|
|
|
|
![]() |
Discussion |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
In addition to an effect on murine cytochrome enzymes, it is possible that grapefruit juice inhibited fungal cytochrome enzymes directly. Whereas we did not test this directly in vitro, we included controls treated with grapefruit juice. It is also possible that the grapefruit juice stimulated some protective host immune defence. However, the timing of grapefruit juice administration (begun on the same day as, or 3 days before, voriconazole treatment) would seem very short to generate such an effect. In any case, the controls given grapefruit juice succumbed at the same rate as controls with no grapefruit juice.
These studies open the possibility of using the mouse model to evaluate voriconazole treatment in a variety of systemic mycoses. This model should also permit comparison of voriconazole with other triazoles and echinocandins, all of which are effective in some murine mycoses.1,1014 As the mouse has been used most commonly for studies of systemic mycoses, and is the least costly and least sentient of the laboratory animals commonly employed, there should additionally be an impetus to use this simple model for comparison of multiple pharmaceuticals and combinations of antifungal drugs.
![]() |
Footnotes |
---|
![]() |
References |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
2 . Sugar, A. M. & Liu, X. P. (2000). Effect of grapefruit juice on serum voriconazole concentrations in the mouse. Medical Mycology 38, 20913.[ISI][Medline]
3
.
Sugar, A. M. & Liu, X. P. (2001). Efficacy of voriconazole in treatment of murine pulmonary blastomycosis. Antimicrobial Agents and Chemotherapy 45, 6014.
4 . Evans, A. M. (2000). Influence of dietery compounds on the gastrointestinal metabolism and transport of drugs. Therapeutic Drug Monitoring 22, 1316.[CrossRef][ISI][Medline]
5 . Singh, B. N. (1999). Effects of food on clinical pharmacokinetics. Clinical Pharmacokinetics 37, 21355. [ISI][Medline]
6 . Walsh, T. J. & Pizzo, P. A. (1988). Nosocomial fungal infections. Annual Reviews of Microbiology 42, 51745.[CrossRef]
7
.
Arikan, S., Lozano-Chiu, M., Paetznick, V., Nangia, S. & Rex, J. H. (1999). Microdilution susceptibility testing of amphotericin B, itraconazole, and voriconazole against clinical isolates of Aspergillus and Fusarium species. Journal of Clinical Microbiology 37, 394651.
8 . National Committee for Clinical Laboratory Standards. (1998). Reference Method for Broth Dilution Antifungal Susceptibility Testing of Conidium-forming Filamentous Fungi. Proposed Standard M38-P. NCCLS, Wayne, PA, USA.
9
.
MacCallum, D. M. & Odds, F. C. (2002). Influence of grapefruit juice on itraconazole levels in mice and guinea pigs. Journal of Antimicrobial Chemotherapy 50, 21924.
10 . Abruzzo, G. K., Flattery, A. M., Gill, C. J., Kong, L., Smith, J. G., Pikounis, V. B. et al. (1997). Evaluation of the echinocandin antifungal MK-0991 (L-743,872) efficacies in mouse models of disseminated aspergillosis, candidiasis, and cryptococcosis. Antimicrobial Agents and Chemotherapy 41, 23338.[Abstract]
11
.
Abruzzo, G. K., Gill, C. J., Flattery, A. M., Kong, L., Leighton, C., Smith, J. G. et al. (2000). Efficacy of the echinocandin caspofungin against disseminated aspergillosis and candidiasis in cyclophosphamide-induced immunosuppressed mice. Antimicrobial Agents and Chemotherapy 44, 23108.
12 . Graybill, J., Bocanegra, R., Luther, M., Fothergill, A. & Rinaldi, M. G. (1997). Treatment of murine Candida krusei or Candida glabrata infection with L-743,872. Antimicrobial Agents and Chemotherapy 41, 19379.[Abstract]
13 . Graybill, J. R., Bocanegra, R., Luther, M. & Loebenberg, D. (1998). SCH56592 treatment of murine invasive aspergillosis. Journal of Antimicrobial Chemotherapy 42, 53942.[Abstract]
14 . Lutz, J. E., Clemons, K. V., Aristizabal, B. H. & Stevens, D. A. (1997). Activity of the triazole SCH56592 against disseminated murine coccidioidomycosis. Antimicrobial Agents and Chemotherapy 41, 155861.[Abstract]