Cyclophosphamide and Thiotepa interaction
Cyclophosphamide and Thiotepa: the Thiotepa prescribing label describes an interaction that usually calls for monitoring, a dose change, or spacing the doses.
Usually manageable with monitoring or a dose change. Tell your pharmacist you take both.
What the FDA labels say
From the Thiotepa (TEPADINA) label · effective 2026-01-30
Hepatic Veno-Occlusive Disease Hepatic veno-occlusive disease may occur in patients who have received high-dose TEPADINA in conjunction with busulfan and cyclophosphamide [ see Adverse Reactions (6.1) ].
In pediatric patients treated with TEPADINA at the recommended dose in combination with busulfan and cyclophosphamide, 8% developed central nervous system toxicity (seizures and intracranial hemorrhage).
The administration of thiotepa with cyclophosphamide in patients reduces the conversion of cyclophosphamide to the active metabolite, 4-hydroxycyclophosphamide; the effect appears sequence dependent with a greater reduction in the conversion to 4-hydroxycyclophosphamide when thiotepa is administered 1.5 hours prior to the intravenous administration of cyclophosphamide…
The reduction in 4-hydroxycyclophosphamide levels may potentially reduce efficacy of cyclophosphamide treatment.
Taking more than these two? Interactions stack. Check your whole list at once; it stays in your browser.
Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.