Журнал фармаконадзора

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Exploring Risk Factors that Contribute to the Onset of Ritodrine-Associated Serious Adverse Drug Reactions

Chiyo Mori, Reiko Yano, Takamasa Sakai, Jinsaku Sakakibara, Kouichi Tanabe, Nobuyuki Goto and Fumiko Ohtsu

Background: Ritodrine is a drug used for threatened premature labor. The severe adverse drug reactions associated with ritodrine are known to be pneumonedema, leukopenia, and rhabdomyolysis, but there have been few investigations on the risk factors. We performed a case-control study and selected case reports as a case group and healthy pregnant women in clinical practice as a control group. Methods: We extracted the onsets of pneumonedema, leukopenia, and rhabdomyolysis associated with ritodrine from case reports in Japan as a case group. We selected healthy pregnant women with ritodrine administration in clinical practice as a control group. We investigated their age, medical history; Pregnancy Induced Hypertension (PIH), multiple pregnancies, concomitant drugs administered, and maximum rate of ritodrine infusion, and examined the association with those factors with the onset of adverse drug reactions by logistic regression analysis. Results: The results of the case group showed: pneumonedema (28 cases); leukopenia (25 cases); rhabdomyolysis (21 cases). The risk factors significantly associated with pneumonedema are a medical history of the cardiovascular system, PIH, multiple pregnancy, and concomitant treatment with steroids, which all match with the precautions in ritodrine’s package insert. The factors associated with leukopenia are its administration longer than 7 days and the concomitant treatment with Mg. The factors associated with rhabdomyolysis are multiple pregnancies and a concomitant treatment with Mg. Conclusion: Risk factors for the onset of pneumonedema match the descriptions in the ritodrine package insert, and can be explained by pharmacological actions. Thus, this study could elucidate the risk factors for rare adverse drug reactions limited to pregnant women. The onsets of leukopenia and rhabdomyolysis were caused by physiological changes by pregnancy and its progression of disease state and ritodrine’s pharmacological action, and were suggested the possibility of risk factors.