Determination of Dexamethasone To 13 pg/g (mL) in Ocular Fluids and Tissues Following Unilateral, Topical Administration

摘要

The application of pharmacokinetics to the study of the efficacy of ocular drugs, the PK/PD relationship, is integral to drug discovery/development. Quantitative analysis of drug in ocular tissues if often challenging. This paper describes a method for determination of the concentration of dexamethasone (DEX) in ocular tissues with a LLOQ of 13 pg/g. Plasma, aqueous humor, vitreous humor, retina, and choroid were analyzed. Instrumentation was HTC PAL, Fisher Scientific Accela Pump and Thermo Fisher Scientific TSQ Quantum Ultra. Reversed phase LC (C-18); gradient conditions; APCI; Thermo TSQ Ultra; Resolution, 0.7 daltons at half peak height; centroid; SRM, DEX. ([~(2)H_(4)]-DEX): m/z velence 393 (397) CAD to 373 (377), loss of HF (-10 volts) (-HF). The +APCI method was observed to be rugged and reproducible and met CDER guidelines. Back calculated concentrations for 13, 27, 53 and 106 pg/mL were -12, 2.6, -9.6 and -1.6percent, respectively. A LLOQ of 13 pg/mL (g) was observed using these conditions. The concentration of DEX in anterior retina samples varied from 0.6 to 2.4 ng/g and 0.9 to 14 ng/mL in the untreated and treated eyes, respectively. The concentration of DEX in posterior retina samples varied from < LLOQ to 1.7 ng/g and < LLOQ to 4.8 ng/mL in the untreated and treated eyes, respectively. The concentration of DEX in anterior choroid samples varied from 1.1 to 6.2 ng/g and 5.0 to 46 ng/mL in the untreated and treated eyes, respectively. The concentration of DEX in posterior choroid samples varied from < LLOQ to 5.2 ng/g and < LLOQ to 4.7 ng/mL in the untreated and treated eyes, respectively. A method is described with an approximate one order of magnitude lower LLOQ for DEX relative to literature methods. This method has been applied to the determination of the pharmacokinetics of DEX in ocular tissues of rabbits and in tissues excised bi-laterally following unilateral topical administration.