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Article Title

Pharmacokinetics of betamethasone disodium phosphate-loaded microparticle following pulmonary delivery

Abstract

Betamethasone (BTM) is a therapeutic agent for the treatment of pulmonary diseases. Betamethasone disodium phosphate (BDP) is a prodrug of BTM and is rapidly converted into BTM after dosing. In this study, intratracheal administration of the dry powder (ITp) of BDP-chitosan microparticle (BDP-CM) was investigated to determine the drug absorption and disposition in New Zealand white rabbits. In addition, intravenous injection (IV) and intratracheal instillation (ITs) of BDP solution were also investigated. The investigated 10% drug-loaded BDP-CM had a narrow size distribution (2.76 ± 0.25 μm), positive zeta potential (40.23 ± 1.98 mV) and low tap density (0.257 ± 0.106 g/cm3). There were no significant differences in AUC, half-life (t1/2) and MRT (mean resident time) among the three delivery routes (p > 0.05), the pharmacokinetics of the three routes could be further evaluated to determine their effects. The t1/2 of ITp, ITs and IV were 236 ± 6 (mean ± SEM), 153 ± 16 and 148 ± 12 min determined from plasma levels, and 220, 141, and 92 min, determined from lung levels, respectively. The MRT of ITp, ITs and IV were 376 ± 138, 231 ± 21 and 217 ± 18 min, determined from plasma levels, and 355, 227, and 150 min, determined from lung levels, respectively. The relative lung and absolute bioavailabilities of BTM for ITp were 222% (ITs as 100%) and 72% (IV as 100%), respectively.

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