En undersøgelse på ældre patienter har vist, at diltiazem hæmmer metaboliseringen af amlodipin, sandsynligvis via CYP3A4 (plasmakoncentrationen øges med cirka 50%, og effekten af amlodipin øges).
A study in elderly patients has shown that diltiazem inhibits the metabolism of amlodipine, probably via CYP3A4 (plasma concentration increases by approximately 50% and the effect of amlodipine is increased).