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

• Published in: Journal of chromatography. B, Analytical technologies in the biomedical and life sciences Analytical technologies in the biomedical and life sciences, 2021-04, Vol.1170, p.122610-122610, Article 122610
• Main Authors: Meng, Tuo, Kosmider, Leon, Chai, Guihong, Moothedathu Raynold, Aji Alex, Pearcy, Adam C., Qin, Bin, Wang, Yan, Lu, Xiuling, Halquist, Matthew S., Xu, Qingguo
• Format: Article
• Language: English
• Subjects: Animals; Anti-Bacterial Agents - analysis; Anti-Bacterial Agents - pharmacokinetics; Antibiotics; Aqueous Humor - chemistry; Chromatography, Liquid - methods; Cornea - chemistry; Corticosteroid; Dexamethasone - analysis; Dexamethasone - pharmacokinetics; Female; LC-MS/MS; Linear Models; Male; Ocular pharmacokinetics; Ophthalmic ointment; Rabbits; Reproducibility of Results; Sensitivity and Specificity; Tandem Mass Spectrometry - methods; Tears - chemistry; Tobramycin - analysis; Tobramycin - pharmacokinetics
• ISSN: 1570-0232; 1873-376X
• DOI: 10.1016/j.jchromb.2021.122610

•A bioanalytical method to simultaneously quantify dexamethasone and tobramycin.•The sensitive, selective method was validated according to FDA regulatory guidance.•Application of the method was proved by an ocular PK study in rabbit tears.•The method can be applied for ocular PK studies of dexamethasone and tobramycin. 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.