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. 2021 Apr 30:1170:122610.
doi: 10.1016/j.jchromb.2021.122610. Epub 2021 Mar 1.

LC-MS/MS method for simultaneous quantification of dexamethasone and tobramycin in rabbit ocular biofluids

Tuo Meng  1 , Leon Kosmider  2 , Guihong Chai  1 , Aji Alex Moothedathu Raynold  1 , Adam C Pearcy  1 , Bin Qin  3 , Yan Wang  3 , Xiuling Lu  4 , Matthew S Halquist  5 , Qingguo Xu  6
Affiliations

LC-MS/MS method for simultaneous quantification of dexamethasone and tobramycin in rabbit ocular biofluids

Tuo Meng et al. J Chromatogr B Analyt Technol Biomed Life Sci. .

Abstract

The complexity of Tobradex® ointment formulation (dexamethasone 0.1 wt% and tobramycin 0.3 wt%) and the high cost of pharmacokinetic (PK) studies in human aqueous humor may prevent generic drug companies from moving forward with a Tobradex®-equivalent product development. The in vitro drug release test would be an alternative approach for differentiating the generic formulations containing both dexamethasone (DEX) and tobramycin (TOB), and the results should be correlated with the in vivo ocular PK studies for further evaluation. To facilitate the in vivo ocular PK studies, a sensitive, rapid and specific liquid chromatography-tandem mass spectrometry (LC-MS/MS) method that can simultaneously quantify both DEX and TOB in rabbit ocular matrices including tear, aqueous humor and cornea was established and validated. The lower limit of quantification (LLOQ) was 1.5 ng/ml for DEX and 3 ng/ml for TOB with good precision and accuracy. Both intra- and inter-batch precisions were within ±15%, and the accuracy for all QCs was within the range of 85-115%. This new method was successfully applied for a pilot pharmacokinetic analysis of DEX and TOB in rabbit tears after topical administration of Tobradex® ointment.

Keywords: Antibiotics; Corticosteroid; LC-MS/MS; Ocular pharmacokinetics; Ophthalmic ointment.

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Conflict of interest statement

Declaration of Competing Interest

The authors declared that there is no conflict of interest.

Figures

Fig. 1:
Fig. 1:
Chemical structure of (A) dexamethasone (DEX) and its internal standard (C) dexamethasone-d5 (DEX-d5); (B) tobramycin (TOB) and its internal standard (D) sisomicin (Siso).
Fig. 2:
Fig. 2:
Schematic workflow of the online diversion LC-MS/MS system. (A) the mobile phases were diverted to the waste. (B) the PFP column was connected to the MS source.
Fig. 3:
Fig. 3:
Representative chromatograms of DEX and DEX-d5 in (A) blank artificial tear solution, (B) blank aqueous humor, (C) blank cornea matrix, and (D) blank artificial tear solution spiked at 1.5 ng/ml DEX (LLOQ) with 125 ng/ml DEX-d5.
Fig. 4:
Fig. 4:
Representative chromatograms of TOB and sisomicin (siso) in (A) blank artificial tear solution, (B) blank aqueous humor, (C) blank cornea matrix, and (D) artificial tear solution spiked at 3 ng/ml TOB (LLOQ) with 250 ng/ml sisomicin.
Fig. 5:
Fig. 5:
Representative chromatograms of (A) DEX and DEX-d5, (B) TOB and sisomicin in rabbit tear fluids samples. (C) Concentration-time curve of DEX and TOB in rabbit tear fluids samples after topical administration of Tobradex® ointment. Mean ± SD, n=6 rabbit tear samples.
See this image and copyright information in PMC

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