PURPOSE: A composition for solubilizing an insoluble drug is provided to enhance solubility of the insoluble drug in water and to easily manufacture a water soluble formulation with easy absorption. CONSTITUTION: A composition for solubilizing an insoluble drug contains the insoluble drug or a prodrug thereof, a solubilizer, a surfactant, a solubility enhancer, and water. The solubilizer is selected from the group consisting of polyethylene glycol, glycerin, and propylene glycol. The surfactant is selected from the group consisting of polysorbate and a polyoxyethylene-polyoxypropylene copolymer. The solubility enhancer is selected from the group consisting of hydroxypropyl beta cyclodextrin and tocopherol-succinic acid-polyethylene glycol. [Reference numerals] (AA) Solubility(ug/ml); (BB) Control example 1; (CC) Example 1-A; (DD) Example 1-B; (EE) Example 1-C; (FF) Example 1-D; (GG) Example 1;물에 난용성의 약물을 효과적으로 가용화할 수 있는 물전달체로서의 주사제용 약학 조성물이 제공된다. 보다 구체적으로, 난용성 약물 또는 그의 프로드러그; 용해보조제; 계면활성제; 용해도 증강제; 및 물을 포함하는 약학 조성물이 제공된다. 상기 조성물은 난용성 약물을 가용화하는 것을 특징으로 한다.