Mô tả
Dexamethasone and methotrexate are commonly combined in oncology regimens; dexamethasone may modestly reduce methotrexate's antifolate toxicity but also reduce some therapeutic activity.
Cơ chế
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).
Ý nghĩa lâm sàng
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.
Xử trí
Follow established oncology protocols; avoid adding dexamethasone to methotrexate-based regimens outside of standardised protocols without oncology guidance.