Key result
Fasting digoxin yields higher peak serum concentrations and AUC than fed dosing despite identical urinary excretion.
Why the study?
Does fasting state compared to fed state alter the measured bioavailability of oral digoxin in human subjects?
Does fasting state compared to fed state alter the measured bioavailability of oral digoxin in human subjects?
Methodological differences in measuring digoxin bioavailability (serum vs. urine) can lead to spurious conclusions about fed vs. fasting states.
Answers are grounded in this paper and cite their sources.
Serum digoxin PK measures may mislead on food effects; leaves open whether urinary excretion better reflects true bioavailability in larger studies.
Three subjects were first given a digoxin tablet in the fasting state and subsequently received the same formulation in the fed state, to simulate a spurious oral bioavailability difference. As expected, when measured by peak serum digoxin concentration as well as by area under the serum digoxin concentration-time curve the bioavailability of digoxin appeared to be higher in the fasting state than in the fed state. However, when measured by cumulative five-day urinary excretion of digoxin bioavailability was identical in both conditions.This simple experiment illustrates the fact that the estimation of bioavailability is subject to considerable methodological error, of which the clinician must be aware when evaluating reports on drug bioavailability in general and of digoxin in particular.
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Sánchez et al. (1973) studied this question. Digoxin tablet in fasting state vs. Digoxin tablet in fed state was evaluated on Bioavailability measured by peak serum concentration, area under the curve (AUC), and cumulative 5-day urinary excretion. Digoxin administration in the fasting state yielded higher peak serum concentrations and AUC than in the fed state, but cumulative 5-day urinary excretion was identical between conditions.
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