Objective: To determine methotrexate (MTX) use and the degree to which Canadian pediatric rheumatologists adhere to the American College of Rheumatology (ACR) guidelines on monitoring for MTX toxicity.
Methods: A 20-item questionnaire was e-mailed to 37 pediatric rheumatologists in 17 centers in Canada. A total of 28 (75.7%) responded.
Results: The oral route (PO) of administration was preferred initially by 78.6% in most cases, but for more severe cases, this fell to 42.8%. Those who chose not to start PO used the subcutaneous route (SQ). When PO was initial treatment, a switch to SQ was undertaken because of dose escalation, lack of efficacy, or GI toxicity. An initial mean dose of 0.35-0.5 mg/kg/wk was prescribed by 51.8%. For 75%, the maximum dose was 1 mg/kg/wk (up to 25 mg). Complete blood count, aspartate aminotransferase (AST), and alanine aminotransferase (ALT) were determined by 100% at baseline and in followup; albumin and creatinine by 85.7% at baseline, but by only 71.4% and 67.8%, respectively, in followup. After a change in dose, 96.3% requested blood tests at least monthly; this was extended to every 6 to 8 weeks by 78.6% when the dose was stable. Side effects of recurrent nausea and/or vomiting were reported to occur frequently. No severe toxicity, and in particular no case of cirrhosis, was reported. Prophylactic folate supplementation was prescribed by almost all physicians.
Conclusion: Most Canadian pediatric rheumatologists follow ACR guidelines to monitor for MTX toxicity in children with rheumatic diseases who were prescribed MTX. The variation in monitoring and response to toxicity raises the question whether specific pediatric guidelines should be developed.