New Ophtalmic Emulsions for the Therapy of Amoebic Keratitis.

Purpose: Amoebae of the genus Acanthamoeba, protozoa ubiquitous in natural environments, are recognized as an opportunistic pathogen causing corneal infections. Contact lens wearers can contract amoebic keratitis. Rokitamycin (RKT) is a macrolide which is strongly inhibitory as regards Acanthamoeba castellanii. New o/w ophthalmic emulsions were developed to control RKT local release, improve ocular drug bioavailability; o/w emulsion also improve patient compliance compared to lipophilic formulations. Methods: Emulsions were prepared by high-shear homogenization methods. Formulative and manufacturing parameters were set. Dimensional, morphological and rheological characterizations were performed. In vitro microbiological studies were carried out to verify the effect of formulations on Acanthamoeba castellanii. The influence of chlorexidine gluconate (CX), used as preservative component, of the anti-protozoo activity of formulation was also evaluated. Results: O/w emulsions were obtained by high-shear homogenization using these processing parameters: 10 min of emulsion time, 20,000 rpm of emulsion rate and 60°C of temperature. The leader formulations selected have mean diameter of about 6-7 µm which remains stable along 4 months. Formulations show typical physical-chemical properties of liquid ophthalmic dosage form in terms of pH, osmolarity and viscosity. Emulsions containing RKT and/or CX decrease growth of Acanthamoeba with regard to dose and time. Particularly formulation included both substances resulted the most efficient. Conclusion: O/w emulsion with high anti amoebic activity was obtained.