Abstract: Objective To investigate the prevalence of and risk factors for thrombocytopenia caused by fluoroquinolones in order to provide reference for rational use of fluoroquinolones. Methods A retrospective study was made of 596 cases of adverse drug reactions (ADR) in two hospitals between Jan 1, 2015 and Dec 31, 2019. According to the diagnostic criteria for thrombocytopenia, these patients were divided into the thrombocytopenia group (44 patients) and non- thrombocytopenia group (552 patients). Univariate and multiple logistic regression analysis was used to identify risk factors related to thrombocytopenia. Results Thrombocytopenia caused by fluoroquinolones accounted for 7.38% of the total ADR. There were 26 cases (59.09%) with platelet counts below 75% of the normal level, 12 cases (27.27%) below 50%~75% of the normal level, and 6 cases (13.64%) below 50% of the normal level. After discontinuation of medication, those symptoms gradually returned to normal. Univariate and multivariate logistic analysis showed that APACHE-II score ≥20 points (OR = 2.09, 95%CI=1.10 to 3.99, P=0.022), creatinine clearance rate≤30 mL·min^-1 (OR=2.01, 95%CI= 1.08 to 3.75, P=0.031), overdose medication (OR= 2.02, 95%CI=1.08 to3.72, P=0.028) and duration of medication ≥14 days (OR=1.95, 95%CI=1.04 to 3.64, P=0.043 ) were independent risk factors for thrombocytopenia caused by fluoroquinolones. Conclusion When patients are using fluoroquinolones, clinicians should be alert to the occurrence of thrombocytopenia, especially among severe cases (APACHE-II score≥20) or cases with renal insufficiency (creatinine clearance ≤30 mL·min^-1), overdose medication and long-term medication (≥14 days).

Key words: fluoroquinolones, levofloxacin, moxifloxacin, ciprofloxacin, pefloxacin, gatifloxacin, thrombocytopenia, risk factors