SHM Converge Scientific Abstract ePoster Gallery-When the Methotrexate Level Is Undetectable: Clinical Recognition of Low Dose Toxicity

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A 75-year-old woman with rheumatoid arthritis on methotrexate and prednisone was brought in confused after several weeks of diarrhea, painful oral intake, and recent cellulitis treated with trimethoprim-sulfamethoxazole. She was cachectic, somnolent, tachycardic, mildly hypotensive, and had oral mucositis. Labs showed macrocytosis, low folate, cytopenias, mild renal dysfunction, and an undetectable methotrexate level.<br /><br />The key teaching point is that methotrexate toxicity can occur even when serum methotrexate levels are undetectable, especially if the patient presents late or has renal dysfunction. In this case, further history revealed that she had accidentally taken methotrexate three times daily instead of once weekly.<br /><br />Management included stopping methotrexate and starting oral folic acid. Her cytopenias improved and mentation normalized by hospital day 4. The presentation highlights several important clinical pearls:<br />- Do not rule out methotrexate toxicity based on a normal or undetectable serum level.<br />- Always verify weekly dosing during medication reconciliation.<br />- Oral mucositis is an early warning sign of methotrexate toxicity.<br />- Monitor closely for renal dysfunction and infection.<br />- Begin folate replacement promptly; oral folate is first-line, while leucovorin may be reserved for patients who do not improve.<br />- Sepsis remains a major cause of morbidity and mortality in severe toxicity.<br /><br />Overall, the case emphasizes that methotrexate toxicity is a clinical diagnosis supported by mucositis, cytopenias, and renal impairment, and that medication dosing errors are a common and preventable cause.

Asset Subtitle

Youssef Saklawi

Meta Tag

Author List Dominique A. Mosley, W. Wyatt Wilson, Youssef Saklawi

Category Clinical Vignettes

Concept Methotrexate Toxicity

Concept Low-Dose Methotrexate

Concept Mucositis

Concept Cytopenia

Concept Serum Methotrexate Level

Distinguished Non-Finalist

Presenter Organization Division of Hospital Medicine, Emory School of Medicine, Atlanta, GA

Presenting Author Youssef Saklawi

Track Adult

Keywords

methotrexate toxicity

undetectable methotrexate level

rheumatoid arthritis

oral mucositis

cytopenias

folate deficiency

renal dysfunction

trimethoprim-sulfamethoxazole

weekly dosing error

medication reconciliation

Methotrexate Toxicity

Low-Dose Methotrexate

Mucositis

Cytopenia

Serum Methotrexate Level