Voriconazole Blood Level and Liver Metabolizing Enzyme in Taiwanese Patients

Condition(s) targeted: Invasive Fungal Infections

Intervention: Blood drawn (lab data) (Other)

Phase: N/A

Status: Not yet recruiting

Sponsored by: National Taiwan University Hospital

Official(s) and/or principal investigator(s):
Shu-Wen Lin, PharmD, MS, Principal Investigator, Affiliation: Graduate Institute of Clinical Pharmacy, National Taiwan University

Overall contact:
Shu-Wen Lin, PharmD, MS, Phone: 886-2-2312-3456, Ext: 88408, Email: shuwenlin@ntu.edu.tw

Voriconazole is an effective antifungal agent and may decrease morbidity and mortality for patients with invasive fungal infections. It is metabolized via liver enzymes. However, these enzymes exhibit different activities in individual patient (genetic polymorphism). Higher proportions of Asians metabolize voriconazole slower than Caucasians and African Americans do. Slower metabolizers may experience dose-associated adverse events more frequently, such as visual disturbances, liver function test abnormalities, and neurological complications. On the other hand, extensive metabolizer or other physiologic conditions may lead to lower blood levels of voriconazole, which may result in treatment failure.

We plan to enroll patient who take voriconazole and examine their liver enzyme activities and blood samples for peak and trough drug levels. We will collect potential factors affecting voriconazole levels, and correlate the levels with the dosing regimen, activity of liver enzyme, occurrence of adverse events, and treatment outcomes. The goal of this study is to determine if monitoring of voriconazole blood levels is necessary in Taiwan.

Official title: Voriconazole Therapeutic Drug Monitoring and CYP2C19 Genetic Polymorphisms in Taiwanese Patients

Study design: Cohort, Prospective

Primary outcome: Relationship between treatment outcome and voriconazole plasma levels

Secondary outcome:

Relationship between voriconazole plasma levels and CYP2C19 polymorphism

Relationship between safety and voriconazole plasma levels

Detailed description: The incidence of opportunistic, invasive fungal infections has dramatically increased over the past two decades and they cause high morbidity and mortality in a variety of patient populations. Voriconazole, a triazole antifungal agent, has shown in vitro activity against many yeasts and a variety of mold and dermatophyte isolates. Voriconazole can be administered either orally or parenterally. It exhibits good oral bioavailability and wide tissue distribution. Voriconazole is extensively metabolized by the hepatic cytochrome P450 isoenzymes, CYP 2C19, CYP 2C9 and CYP 3A4. The affinity of voriconazole is greatest for isoenzyme CYP 2C19 which exhibits genetic polymorphism with 15-20% of Asian populations being poor/slow metabolizers, whereas the prevalence is much lower (3-5%) amongst Caucasians and African Americans. Studies conducted in Caucasian and Japanese healthy subjects have demonstrated that poor metabolizers have, on average, four times higher voriconazole AUC than homozygous extensive metabolisers, while the AUC of heterozygous extensive metabolizers is two times higher than that of homozygous extensive metabolizers. The most commonly reported adverse events associated with voriconazole use include visual disturbances, liver function test abnormalities, and neurological complications. All of them have been reported to be associated with higher plasma concentrations and / or doses. In term of efficacy, an analysis showed a trend toward worse outcomes in patients with voriconazole plasma concentrations < 0. 5 μg/mL although this remains controversial. Since Asians have more CYP 2C19 polymorphism, we expect to see more patients with a wider range of voriconazole plasma concentrations than in previous studies in Caucasian patients. Our study will likely provide stronger evidence in explanation of the relationship between voriconazole plasma concentrations and clinical observations.

We plan to enroll patient who take voriconazole and examine their CYP 2C19 genotypes and plasma samples for peak and trough concentrations. We will collect potential confounding factors affecting voriconazole plasma concentrations, and correlate the concentrations with the dosing regimen, presence or absence of CYP 2C19 polymorphism, occurrence of adverse events, and treatment outcomes. The result of this study will be beneficial in clarify the international debate on controversial issue in the voriconazole plasma concentration monitoring. The ultimate goals of this study is to determine if monitoring of voriconazole plasma concentrations is desired in select patient populations or under certain circumstances in Taiwan.

Minimum age: N/A. Maximum age: N/A. Gender(s): Both.

Criteria:

Inclusion Criteria:

- Hospitalization patient or ambulatory patients

- Patients with invasive fungal infections

- Patients who take PO/IV voriconazole more than 3 days

Exclusion Criteria:

Shu-Wen Lin, PharmD, MS, Phone: 886-2-2312-3456, Ext: 88408, Email: shuwenlin@ntu.edu.tw

National Taiwan University Hospital, Taipei 100, Taiwan

Related publications:

Brüggemann RJ, Donnelly JP, Aarnoutse RE, Warris A, Blijlevens NM, Mouton JW, Verweij PE, Burger DM. Therapeutic drug monitoring of voriconazole. Ther Drug Monit. 2008 Aug;30(4):403-11.

Starting date: October 2008
Ending date: July 2011
Last updated: September 2, 2008