Objective: Ritodrine, a β agonist, is a uterine tocolytic agent used to suppress preterm labor. In 2013, the European Medicines Agency (EMA) recommended that short-acting β agonists should be used for a maximum of 48 h. However, in Japan, they are widely used for long-term therapy (＞48 h). The EMA recommendation was informed to physicians by pharmacists. We retrospectively evaluated the safety of ritodrine by comparing outcomes before and after the provision of drug information (DI). We investigated whether the physicians' knowledge of the DI of ritodrine influenced performance, and affected the dose administered and the number of side effects reported.Methods: Women administered ritodrine for preterm labor between November 2011 and December 2015 were included in this single-centered retrospective study, which comprised two groups: before (Pre, from November 2011 to November 2013) and after (Post, from December 2013 to December 2015) DI provision. The frequency of cardiovascular side effects was the primary endpoint and the rate of long-term use was the secondary endpoint. The chi-squared test was used for statistical comparison and p＜0.05 was considered to indicate a significant difference.Results: The study comprised 91 patients administered ritodrine for preterm labor: 43 in the Post and 48 in the Pre. The frequency of cardiovascular side effects was 48.8 and 45.8 % in the Post and Pre, respectively (p＝0.64). The rate of long-term use was 65.1 and 79.2 % in the Post and Pre, respectively (p＝0.13).Conclusion: The DI provided by pharmacists increased physicians’ awareness of ritodrine use, which may have improved the safety of the drug. Thus, the provision of DI by pharmacists may enhance patient safety by promoting behavioral change in physicians.