Pets with severe hypotension, sick sinus syndrome, 2nd or 3rd degree AV block, acute myocardial infarction, or pulmonary congestion should not take diltiazem. Elderly pets, pets taking beta blockers, or pets with liver or kidney failure should take diltiazem with caution. Due to the potential teratogenic qualities of diltiazem, it should only be given to pregnant pets if the benefits outweigh the risks to the baby.
Pets taking diltiazem with cyclosporine, digoxin, or quinidine should be monitored closely, as the levels of diltiazem may be affected. Cimetidine and ranitidine might cause an increase in the plasma levels of diltiazem. Diltiazem might increase the bioavailability of propranolol.