Interactions between diltiazem and isoflurane. An in vitro investigation in isolated guinea pig atria.

Maximum force of contraction of paced, isolated guinea pig atria was measured in three groups. Atria from animals in group 1 were exposed to isoflurane for 10 min. In group 2, atria were exposed to diltiazem 35 nmol litre-1 alone and in group 3 atria were pre-treated with diltiazem 35 nmol litre-1 before exposure to isoflurane. Maximum depression of contraction was significantly greater in tissue exposed to the combination of diltiazem and isoflurane (group 3) compared with that exposed to isoflurane alone (group 1). Tissue exposed to diltiazem and isoflurane remained significantly more depressed from 15 to 30 min after the administration of isoflurane compared with the depression produced by the volatile agent alone. The results suggest that the calcium antagonist, diltiazem, may modify the effects of isoflurane on myocardial function.