Prolonged administration of ritodrine hydrochloride in women with premature labor or threatened premature delivery based on empirical data in Japan.

In Japan, maintenance tocolysis has been conventionally administered. The current study aimed to identify the annual trends in the prolonged administration of ritodrine hydrochloride and its differences in terms of region and type of facility. This study used data from the Japanese Diagnosis Procedure Combination inpatient database, and the survey included women with premature labor or threatened premature delivery based on the International Statistical Classification of Diseases and Related Health Problems, 10th Revision, codes. The primary outcome was prolonged administration of ritodrine hydrochloride, defined as treatment for ≥ 4 days. The primary exposures were type of institution, regions where the institutions are located, and year at admission. The effect of each exposure on prolonged administration was assessed via multivariate-modified Poisson regression analysis. Of 280,734 female participants, 180,674 received prolonged administration of ritodrine hydrochloride. Women in primary hospitals had a significantly more prolonged duration of administration than those in tertiary hospitals. Prolonged administration was significantly more common in Hokkaido, Chubu, Kansai, and Shikoku than in Tokyo. Conversely, Kyushu had a significantly lower adusted risk ratio than Tokyo. The prolonged administration of ritodrine hydrochloride has been gradually decreasing annually. However, the rate differed in terms of regions and type of facility.