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methotrexate, drug monitoring, laboratory tests
Introduction: There have been no large-scale studies looking at the efficacy and safety of methotrexate. Prior research by our team investigated whether certain monitoring practices were associated with lab abnormalities resulting in clinically relevant events (CREs) within the first 90 days of methotrexate treatment and concluded that dermatologists may consider postponing lab monitoring until 15 days after methotrexate initiation in patients without concerning baseline disease. This follow-up study was performed to determine when within the first 90 days of treatment CREs were most likely to occur and to define the specific numeric values at which abnormal labs resulted in a CRE.
Methods: The medical records of 243 dermatology patients were retrospectively reviewed.
Results: Week 11 had the highest percentage of CREs (11.1%, p=0.00003), with slight peaks at weeks 2 and 5. ALT (22%) and AST (27%) were the most commonly abnormal labs, and elevated ALT (p=0.00087) and AST (p=0.03) values were significantly higher in CREs.
Discussion: This data suggests that lab frequency can be reduced within the first few months; optimal timing of lab draws may be around weeks 2-5 and 11-12. In summary, we found that 1) abnormal labs most frequently led to a CRE at week 11 of monitoring, 2) ALT and AST were the most frequently abnormal labs, and 3) abnormal ALT and AST values were significantly higher in patients with CREs. This study provides valuable insight into an understudied dermatologic topic and hopefully will inform clinicians regarding methotrexate laboratory monitoring and spur further investigation.
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