Provided is a drug composition containing dorzolamide or a salt thereof and timolol or a salt thereof, said novel drug composition being capable of exhibiting an adequate antiseptic effect, even if a container is opened and closed repeatedly. The pharmaceutical composition of the present invention, containing dorzolamide or a salt thereof, and timolol or a salt thereof, does not contain benzalkonium chlorides, and is stored in a reusable container. The present invention further pertains to a method for improving antiseptic effect by further including dorzolamide or a salt thereof in a drug composition kept in a multi-dose vial, said drug composition containing timolol or a salt thereof and not containing benzalkonium chlorides.提供一種新穎之醫藥組成物，其含有多佐胺(dorzolamide)或其鹽及噻嗎洛爾(timolol)或其鹽，即便反覆開關容器而使用，亦能夠充分發揮防腐效果。本發明之含有多佐胺或其鹽及噻嗎洛爾或其鹽之醫藥組成物不含氯化苄烷銨(benzalkonium chloride)，且被裝於多劑量(multidose)型容器。本發明亦關於一種提高防腐效力之方法，其藉由使含有噻嗎洛爾或其鹽，且不含氯化苄烷銨之被裝於多劑量型容器之醫藥組成物中，進而含有多佐胺或其鹽而提高防腐效力。
