Assessment of the efficacy, optimal dosage, and safety of diltiazem in early treatment of unstable angina pectoris

BACKGROUND: The anti-ischemic benefits of diltiazem are well recognized; however, there are fewer studies of the use of intravenous diltiazem for early treatment of unstable angina pectoris (UAP). HYPOTHESIS: The present study prospectively evaluated the efficacy, optimal dosage, and safety of continuous intravenous diltiazem for initial management of UAP. METHODS: In all, 102 patients with UAP were recruited in this multicenter trial. Diltiazem was administered as a continuous intravenous infusion with a fixed incremental dosage of 1,3, and 5 microg/kg/min, titrated according to the patients' symptoms of angina, and then was maintained for a further 48 h at the angina-free dose. Episodes of angina, hemodynamic stability, and complications were observed. RESULTS: Angina was adequately controlled with continuous intravenous infusion of diltiazem in 64 patients (63%) at a dosage of 1 microg/kg/min, in 26 patients (25%) at dosage of 3 microg/kg/ min, and in 6 patients (6%) at dosage of 5 microg/kg/min, leading to a cumulative effective ratio of 94% in all patients. Additional anti-ischemic medications were required in six patients (6%) who had refractory angina. Bradyarrhythmias noted in only six patients (6%) were reversible after decreasing the dosage of diltiazem. No acute myocardial infarction or other severe side effects occurred. CONCLUSION: Continuous intravenous infusion of diltiazem is well tolerated and relieves symptoms rapidly and effectively in up to 94% patients with UAP, with the majority (63%) treated at the low dosage of 1 microg/kg/min. Diltiazem can be used as a first-line anti-ischemic agent for early conservation treatment of UAP.