Voriconazole dosing is weight based but current evidence does not support that clearance substantially increases with increasing body weight in obese patients (Eljaaly and Nix)
A retrospective study found higher IV mean trough concentrations and rates of supratherapeutic troughs in obese versus nonobese patients dosed on total body weight (6.2 vs 3.5 mg/L, p <0.0001, 67% vs 17%, p <0.0001, respectively) (Koselke et al.)
Another retrospective study found that IV voriconazole random levels were significantly higher in patients with a BMI 25 kg/m² or greater versus a BMI <25 kg/m² (6.4 vs 2.8 mg/L, p = 0.04) but no difference was found with oral voriconazole (Davies-Vorbrodt et al.)
Using total body weight in obese patients could lead to higher exposure and toxicity of voriconazole and the IV vehicle of cyclodextrin
Eljaaly K and Nix DE. Voriconazole dosing in obese patients. Clin Infect Dis. 2016. 63: 286-7.
Koselke E, Kraft S, Smith J, et al. Evaluation of the effect of obesity on voriconazole serum concentrations. J Antimicrob Chemother. 2012. 67: 2957-62.
Davies-Vorbrodt S, Ito JI, Tegtmeier BR, et al. Voriconazole serum concentrations in obese and overweight immunocompromised patients: a retrospective review. Pharmacotherapy. 2014. 33: 22-30.