説明
Dexamethasone and methotrexate are commonly combined in oncology regimens; dexamethasone may modestly reduce methotrexate's antifolate toxicity but also reduce some therapeutic activity.
機序
Dexamethasone upregulates DHFR (dihydrofolate reductase), the target enzyme of methotrexate, potentially reducing cytotoxic efficacy while also partially protecting normal rapidly dividing cells; the net effect depends on the clinical context (cancer type, regimen).
臨床的意義
In haematological malignancies where both drugs are protocol-specified, the combination is deliberately used (e.g., HyperCVAD); interaction is a pharmacodynamic consideration rather than a contraindication.
対処法
Follow established oncology protocols; avoid adding dexamethasone to methotrexate-based regimens outside of standardised protocols without oncology guidance.