| Abstract: | The Lopressor Intervention Trial (LIT) was a double-blind, randomized,placebo-controlled, multicentre study designed to evaluate theeffect of oral metoprolol on overall mortality in patients survivinga recent acute myocardial infarction. Patient enrollment beganin August 1979 and ended on 15 April 1982, with 2395 patients(1200 on placebo and 1195 on metoprolol). Hospitalized patients,45 to 74 years of age, began therapy from 6 to 16 days aftertheir myocardial infarction. Following a short titration period,maintenance therapy with metoprolol 100 mg b.i.d. or placebowas continued for up to 1 year. Enrollment was prematurely terminatedbecause of a progressive and marked decline in patient accession;it was not feasible to reach the original goal of 3200 patientsin a practical period of time. This target sample size was basedon an anticipated 1 year placebo mortality rate of 10%, a 50%reduction in total mortality with metoprolol and premature discontinuationof study medication in no more than 15% of patients in the metoprololgroup. Two primary analyses were planned: total mortality amongall randomized patients at 7 and at 12 months of trial entry.After7 months of treatment there were 54 deaths in the placebo groupand 42 deaths in the metoprolol group. After 1 year there were62 deaths in the placebo group and 65 in the metoprolol group.Thus, the 1 year placebo mortality rate of 5.2% was half thatpredicted at the outset. In addition, study medication was prematurelydiscontinued in over 30% of patients in the metoprolol group.At termination, the power of the study was found to be too lowto reliably detect the mortality reduction reported recentlyby other studies. Hence the results of LIT are deemed inconclusive. |
