New HPLC-UV analytical method for quantification of metronidazole: Application to ex vivo ocular kinetic assessments following the administration of thermosensitive ocular in situ gel

Metronidazole eye drops have been used to treat Acanthamoeba keratitis. However, ophthalmic preparations also have some limitations, one of which is the rapid elimination of the drug, that reducing the effectiveness of the drug. Accordingly, an alternative delivery approach can be applied to overcome this issue. Additionally, as one of critical steps in the formulation development, analyitical methods that allow the quantification of metronidazole in ex vivo corneal permeation and deposition should also be developed. Here, we report a validated high- performance liquid chromatography method (HPLC-UV) according to ICH guidelines for the measurements of metronidazole concentrations following formulation of thermosensitive ocular in situ gel and its administration in ex vivo porcine corneas. The development of extraction techniques and optimization of HPLC conditions were optimized using analytical quality by design. XselectTM CSHTM C18 HPLC column (Water, 3.0 × 150 mm, particle size 3.5 m) was used to separate all analytes by isocratic elution with mobile phases of acetate buffer and acetonitrile with LLOQ value of 0.08 μg/mL. The resulting method proved to be selective, precise, and accurate and was succefully applied to determine ocular kinetic profiles of metronidazole from thermosensitive ocular in situ gel in ex vivo porcine corneas, showing that this approach was able to improve the concentration of metronidazole in the corneal tissues. We, therefore, suggested that HPLC-UV approach developed in this study has the potential to be used in drug release evaluation, therapeutic drug control research, ocular kinetics, and toxicological evaluation.