Pharmacokinetics of Voriconazole in Obese Subjects
Pharmacokinetics of Voriconazole in Obese Subjects
Obese subjects may require a higher fixed oral maintenance dosing regimen of voriconazole
 compared to normal weight subjects to achieve comparable plasma exposures. The current study
 is designed to address this issue.
The prevalence of obesity has increased tremendously in the past two decades. An estimated 1
 out of 5 persons in the United States are classified as obese. Under representation of obese
 patients in pharmacokinetic trials grossly limit generalizability of drug dosing
 recommendations in this emerging population. No published pharmacokinetic studies of
 voriconazole dosing in patients with obesity currently exist in the literature.
 Specifically,voriconazole pharmacokinetic data from subjects with a body mass index (BMI) ≥
 35 kg/m2(Class II and III obesity) are limited.

 Voriconazole is available as both an intravenous and oral formulation. Anecdotal experience
 suggest that the use of oral voriconazole to be significantly more prevalent that that of
 intravenous therapy. The current oral recommended dosing regimen for voriconazole includes
 use of 200 mg every 12 hours for patients who are over 40 kg. The dosage can be increased to
 300 mg by mouth every 12 hours in situations where a sufficient clinical response is not
 noted. A weight based dosing strategy is also utilized in patients with more serious
 infections (3-6 mg/kg IV Q 12 hours) such as invasive aspergillosis. Voriconazole
 demonstrates non-linear pharmacokinetics and so dosing based on total body weight may result
 in non-dose proportional exposure. For example, a 1.5 fold dose increment in voriconazole
 from 200 mg to 300 mg every 12 hours results in a 2.5 fold increase in exposure. The most
 appropriate body size descriptor is unknown (i.e. ideal body weight, fat free weight, lean
 body weight, etc.) for most antimicrobials, including voriconazole. As a consequence, the
 appropriateness of weight-based voriconazole dosage selection in obese patients is not known.
 Intuitively, weight based dosing (on total body weight) in this population could lead to
 higher than expected exposures (non-linear pharmacokinetics) and lead to potential adverse
 events. Therapeutic drug monitoring is increasingly advocated as a system to improve
 voriconazole dosing. However, an assay to measure voriconazole concentrations in the clinic
 is not routinely available. Hence, the current pilot study proposes to characterize the
 pharmacokinetic profile of voriconazole in obese subjects using two fixed dose regimens.
Inclusion Criteria:

 1. males and females, 18 to 50 years of age;

 2. non-smoking or light-smoking (≤5 cigarettes per day) volunteers;

 3. BMI ≥ 35 kg/m2;

 4. female subjects of childbearing potential either surgically sterilized, using an
 effective method of contraception (diaphragm, cervical cap, condom) or agree to
 abstain from sex from time of prestudy screening, during entire study period and 1
 week following the study period.

 Exclusion Criteria:

 1. History of significant hypersensitivity reaction or intolerance to voriconazole,
 fluconazole,itraconazole, posaconazole, or ketoconazole ;

 2. history of significant clinical illness requiring pharmacological management;

 3. abnormal serum electrolyte or complete blood count requiring further clinical work-up;

 4. transaminases (AST or ALT) >2.5 x upper limit of normal;

 5. estimated creatinine clearance <50 mL/min (Cockcroft-Gault equation);

 6. positive urine pregnancy test (if female);

 7. abnormal electrocardiogram (ECG) as judged by study physician;

 8. unable to tolerate venipuncture and multiple blood draws;

 9. clinically significant abnormal physical examination defined as a physical finding
 requiring further clinical work-up.