Influence of switching from intravenous to oral administration on serum
voriconazole concentration
Abstract
Background: While bioavailability of oral voriconazole is known to be
>90%, several reports have observed much lower oral
bioavailability. The aim of the present study was to assess the oral
bioavailability of voriconazole in clinical use by evaluating the change
in serum voriconazole concentration in patients who received
intravenous-to-oral switch therapy with the same dose of voriconazole.
Methods: A single-center, retrospective cohort study was conducted at
the 614-bed Gifu University Hospital in Japan. Patients who received
intravenous-to-oral switch therapy with the same dose of voriconazole
between January 1, 2011 and December 31, 2018 were enrolled in the
present study. We evaluated changes in serum voriconazole concentration
before and after switch therapy. Results: Voriconazole trough
concentrations significantly decreased following oral compared to
intravenous treatment (2.5 ± 1.5 µg/mL vs 3.3 ± 2.0 µg/mL, P = 0.021).
The median change rate of serum concentration by switching the route of
administration was 82.7%, with wide inter-individual variability (range
27.2–333.3%). Further, young age (OR 1.04, 95% CI 0.99–1.08, P =
0.090) and low blood urea nitrogen (OR 1.11, 95% CI 0.99–1.24, P =
0.070) were found to be close to significant factors associated with
decreased serum concentration. Conclusions: Switching from intravenous
to oral treatment resulted in a significant decline in voriconazole
trough concentrations with wide inter-individual variability. Therefore,
measurement of serum concentration for dose adjustment should be
performed after switching to the oral form.