To prevent constipation, maintain diet adequate in fiber, drink plenty of water, and exercise. Coadministration of diltiazem with rifampin or any known CYP3A4 inducer should be avoided when possible, and alternative therapy considered. To prevent constipation, maintain diet adequate in fiber, drink plenty of water, and exercise. In ten-subject study, coadministration of diltiazem 120 mg bid with lovastatin resulted in 3- to 4-fold increase in mean lovastatin AUC and Cmax vs. Previous next Report Problems to the Food and Drug Administration You are encouraged to report negative side effects of prescription drugs kjop billige generisk tiazac to the FDA. To reduce the risk of dizzy or fainting spells, do not sit or stand up quickly, especially if you are an older patient. Diltiazem can cause mildly abnormal liver tests that usually return to normal with discontinuation of the medication.