Background: Duloxetine (Cymbalta®) is classified as a selective serotonin and norepinephrine reuptake inhibitor (SSNRI). The FDA approved it for major depressive disorder (MDD), fibromyalgia and peripheral neuropathic pain associated with diabetic neuropathy (DN) in August 2004. Due to the extent of renal clearance (70%) of both the parent drug and its metabolites, duloxetine is also not recommended for use in patients with severe renal impairment (estimated creatinine clearance <30 mL/min). The National Health Insurance issued that the maximum dosage for fibromyalgia and diabetic peripheral neuropathic pain is 60 mg once daily.
Objectives: This study explores the rationality of the duloxetine usage.
Methods: This is a retrospective study in a regional hospital in central Taiwan. Cases were obtained from January 2018 to October 2018 for all outpatients using duloxetine. The rationality assessment of duloxetine prescribing included indications, maximum dose and dose adjustment for renal dysfunction. Descriptive statistical analysis was performed in the study.
Results: Total 589 cases were recruited in the study. The maximum dose of all patients was less than 60mg once daily. The dose of 359 cases (60.9%) were according to National Health Insurance guidance. Another 230 cases (39.1%) did not follow the guidance. In the 230 cases, 208 (90.4%) of them have no relevant indications and 38 cases (6.45%) were severe renal impairment (estimated creatinine clearance <30 mL/min) and should be avoided to use.
Conclusions: This study showed that the improper use of duloxetine was 39.1%. This was result of miscoding of ICD9 corresponding to ICD10 diagnostic code. Therefore, the computerized physician order entry (CPOE) system was revised, and dose adjustment was implemented on renal function impairment patients directly when physicians prescribe duloxetine on January 2020. This study demonstrated the pharmacist- intervention and collaboration with the physician reduced the medical expenses.
