Investigation of surfactants suitable for stabilizing of latanoprost

The content of latanoprost, a therapeutic drug for glaucoma, is likely to decrease in solution. In a previous study, we confirmed that this was associated with latanoprost adsorption to the container and hydrolysis of latanoprost, and established a formulation of latanoprost eye drop solution that can be stored at room temperature. In addition, we clarified that a surfactant added to the formulation stabilized latanoprost by forming complex micelle. In this study, we investigated the influence of structure of surfactants in the stabilization of latanoprost. Non-ionic surfactants involving the polyoxyethylene chain (additive mol number: 20 or more) and the straight-chain alkyl group, with an HLB of 15.0 or more, markedly inhibited a decrease in the latanoprost content and its degradation. These surfactants are soluble in the formulation of eye drop solution, leading to micelle formation even at a low concentration, and they are not influenced by the temperature. Therefore, they may exhibit marked stabilization effects. In addition, there was no influence on the stability of latanoprost when adding benzalkonium chloride, as a preservative, to a formulation involving these surfactants.