The present invention relates to a pharmaceutical formulation for oral administration for preventing or treating allergic rhinitis or asthma, which comprises: (a) a first particle part comprising levocetirizine or a pharmaceutically acceptable salt thereof and an organic acid； and (b) a second particle part comprising montelukast or a pharmaceutically acceptable salt thereof. The pharmaceutical formulation according to the present invention comprises an organic acid as a stabilizing agent, which can effectively inhibit the production of levocetirizine and montelukast related substances, and thus, show good stability.本發明是有關於一種用於預防或治療過敏性鼻炎或氣喘之供口服投藥的藥學配方，其包含有：(a)一包含有左旋西替利或其一藥學上可接受的鹽類和一有機酸的第一顆粒部分；以及(b)一包含有蒙特魯卡斯特或其一藥學上可接受的鹽類的第二顆粒部分。依據本發明的藥學配方包含有一有機酸作為一安定劑，它可有效地抑制產生左旋西替利和蒙特魯卡斯特相關的物質，並且因此，顯示好的安定性。
