Hanselin M.R., Vande Griend J.P., Linnebur S.A. INR elevation with maitake extract in combination with warfarin. Ann Pharmacother. 2010;44(1):223–224.
Rationale
Warfarin dosing is narrow-windowed — INR drift means bleeding or clotting risk. Interactions with supplements are frequently underreported; this case documented one for maitake.
Methods
A case report with serial INR measurements: a patient stable on warfarin added a maitake extract; INR rose. On discontinuing the extract, INR returned to the target range — a dechallenge-consistent pattern.
Results
INR elevation coincided with maitake intake and normalized after withdrawal — the classic single-patient causality signal (positive dechallenge).
Conclusions
A documented interaction signal: maitake can potentiate warfarin. One case is the weakest evidence tier, but for INR-destabilization it is exactly the kind of signal that matters clinically.
Worth noting
The mechanism is plausible via polysaccharide/fiber effects on vitamin K handling or direct anticoagulant activity, but unproven. For readers on warfarin or similar anticoagulants: maitake extract is not a neutral food at this dose — INR monitoring applies.