The starting dose of Cartia XT to treat hypertension ranges from 180 to 240 mg once daily. To treat angina, the starting dose range is 120 or 180 mg once daily. Cartia XT may interact with amiodarone, buspirone, carbamazepine, cimetidine, cyclosporine, digoxin, lovastatin, rifampin, quinidine, sedatives, antibiotics, antifungal medications, beta-blockers, or HIV/AIDS medicines.