In situ gelling microemulsion for topical ocular delivery of moxifloxacin and betamethasone

Abstract

This article proposes an in situ gelling microemulsion for the ocular delivery of moxifloxacin (MOX) combined with betamethasone (BET) for use as a topical formulation throughout the postoperative period following eye surgery. Thermal analyses indicated compatibility between the drugs and the selected excipients. The microemulsion presented parameters that guarantee ocular tolerability: a droplet size of 28.0 ± 0.1 nm (polydispersity index = 0.11 ± 0.01), a zeta potential of −10.3 ± 0.1 mV, a pH of 7.1 ± 0.1, and osmolarity of 579.0 ± 9.4 mOsmol kg−1. The formulation had an ideal gelling temperature for the ocular surface (32.8 ± 0.9 °C), which allowed precise dosing due to its liquid state at storage temperatures. When the drugs’ release was assessed in vitro, the microemulsion was shown to prolong both drugs’ release compared with controls. Last, ex vivo drug penetration tests were performed in porcine corneas under static conditions (i.e., left in contact with the corneal surface) or with a simulated tear flow. In static conditions, the microemulsion increased MOX’s penetration into the cornea but decreased BET’s compared with the control. However, when the formulation was subjected to a simulated tear flow throughout its corneal application, the microemulsion made MOX’s penetration statistically similar to that in static conditions, which was 2–3 times (p less than 0.05) greater than that provided by the control, while maintaining the same BET penetration level as the control. Altogether, the proposed in situ gelling microemulsion seems to be a convenient, effective alternative for use following intraocular surgery.