Pharmacokinetics, pharmacodynamics, and comparative bioavailability of single, oral 2-mg doses of dexamethasone liquid and tablet formulations: a randomized, controlled, crossover study in healthy adult volunteers.

Background: Dexamethasone is a glucocorticoid used widely worldwide for immunosuppressive treatment, allergies, bronchiolitis, and croup, among others. For children, liquid formulations are especially suitable because, compared with other dosage forms, both exact dosing and proper intake are facilitated.

Objective: The objective was to evaluate the pharmacokinetics, pharmacodynamics, and comparative bioavailability of a commercial liquid oral dexamethasone formulation intended for pediatric use relative to those of a tablet.

Methods: In a randomized, controlled, crossover study in 24 healthy adult volunteers, we administered single doses of the liquid and tablet formulation, containing 2 mg of dexamethasone each. Blood samples were taken up to 24 hours postdose. Quantification was carried out using a validated specific and sensitive high-pressure liquid chromatography with UV detector method. Noncompartmental pharmacokinetic parameters were compared between treatments according to European Medicines Agency (EMA) bioequivalence guidelines. For AUC(0-t) and C(max), the 90% CI for the ratio of the test and reference products should be contained within the predetermined acceptance interval of 80% to 125%. As a pharmacodynamic variable, we measured suppression of endogenous cortisol (predose and postdose).

Results: Both preparations showed similar pharmacokinetic and pharmacodynamic profiles but high between-subject variability of pharmacokinetic key parameters and endogenous cortisol concentrations (>30%). Mean AUC(0-t), AUC(0-∞), and C(max) were 37.8 ng/mL/h, 46.0 ng/mL/h, and 9.35 ng/mL, respectively, for the liquid and 41.3 ng/mL/h, 48.1 ng/mL/h, and 9.17 ng/mL, respectively, for the tablet formulation. T(max) was 0.89 hour (liquid) and 0.97 hour (tablet). The point estimates and 90% CIs for AUC(0-t), AUC(0-∞), and C(max) ratios (liquid vs tablet) were 91.42% (82.05%-101.86%), 95.72% (84.46%-108.5%), and 102.04% (86.94%-119.76%), respectively. Thus, point estimates and 90% CIs were within the bioequivalence range of 80% to 125% for all relevant parameters, including the pharmacodynamic parameter AUEC (area under the effect curve).

Conclusions: This single-dose study suggests that the test and reference products met the EMA regulatory criteria to assume bioequivalence in these fasting healthy male and female volunteers. German Register of Clinical Trials registration number: DRKS00000785.