[Serious complications during treatment with methotrexate: also in chronic low-dosage use]

Area of Science:

• Pharmacology
• Toxicology
• Rheumatology

Background:

• Methotrexate is a widely used medication for inflammatory conditions like psoriatic arthritis and rheumatoid arthritis.
• Low-dose methotrexate is generally considered safe, but potential serious adverse events require careful consideration.

Observation:

• Two cases of severe methotrexate toxicity are presented in elderly male patients.
• One patient developed multi-organ failure due to sepsis and methotrexate intoxication secondary to renal dysfunction.
• The second patient experienced pancytopenia and methotrexate-induced pneumonitis.

Findings:

• Deteriorating renal function significantly increases the risk of methotrexate intoxication.
• Methotrexate toxicity can manifest as multi-organ failure, pancytopenia, and pneumonitis.
• Co-medication and pre-existing conditions like impaired kidney function are critical risk factors.

Implications:

• Frequent monitoring of blood counts, renal, and liver function is essential during methotrexate therapy.
• Clinicians must be vigilant for risk factors predisposing to methotrexate intoxication.
• Prompt administration of intravenous folinic acid is critical when methotrexate toxicity is suspected.