In the short-term,
aprepitant increases the AUC of
dexamethasone (by about 60%) and
methylprednisolone (by up to 2.5-fold). Fosaprepitant, a prodrug of
aprepitant, would be expected to interact similarly.
The manufacturer recommends that the usual dose of
dexamethasone should be reduced by about 50% when given with
aprepitant. In
clinical studies a
dexamethasone regimen of 12 mg on day one and 8 mg on days 2 to 4 was used, and this is the recommended regimen. They also recommend that the usual dose of
intravenous methylprednisolone is reduced by 25%, and the usual oral dose by 50%, in the presence of
aprepitant. However, the manufacturer also notes that during continuous treatment with
methylprednisolone, levels would be expected to decrease over the following 2 weeks.