John A. Thompson; Jennifer S. Love; Robert G. Hendrickson
Corresponding Author: John A. Thompson; Oregon Poison Center; Department of Emergency Medicine - Oregon Health & Science University. Email: johnth@ohsu.edu
Section: Research Letter
Publication: 11/11/2021
Background: Methotrexate is a folate analog prescribed for varying disease with weekly administration as opposed to daily. Dosing errors can prove clinically significant and sometimes fatal. Methods: We performed a retrospective poison center review of methotrexate calls between 2009-2019. Results: Of 111 human related poison center calls, most patients taking methotrexate were women ages 41-80 years old, and prescribed methotrexate for rheumatoid arthritis. 88 (79%), and 41 (36%) were admitted to the hospital. 31 (75%) of hospitalized patients received leucovorin treatment for their exposure. Two patients died from methotrexate dosing errors. Discussion: Most methotrexate accidental ingestions reported to poison centers result from dose frequency errors. However, we note a higher incidence of unintentional therapeutic errors (79% v. 13.7%) than reported in the National Poison Data System (NPDS) in 2019. Patients are often hospitalized for lab monitoring and many receive leucovorin. Conclusions: Most methotrexate calls to our poison center resulted from taking the drug more often than prescribed. Efforts may focus on patient education, physician or pharmacist monitoring during initiation, improved dispensing devices, or weekly drug dispensing.