It is intended to produce eye drop preparations containing prostaglandin derivatives which are hardly soluble in water and liable to be adsorbed by resin containers or prostaglandin derivatives which are liable to decompose when dissolved in water. The solubility of prostaglandin derivatives in wate r can be improved and the adsorption thereof by resin containers can be remarkably inhibited by adding nonionic surfactants such as polysorbate 80 o r polyoxyethylene-hardened castor oil 60 to eye drops. Moreover, the decomposition of prostaglandin derivatives can be remarkably inhibited by adding antioxidants such as disodium ethylenediaminetetraacetate or dibutylhydroxytoluene.
