Early treatment with intravenous metoprolol for suspected acute myocardial infarction: a phase IV United States trial. Phase IV Metoprolol in Myocardial Infarction Study Group.

Recent randomized clinical trials have shown that total mortality and cardiovascular mortality are reduced by the early intravenous administration of beta-blockers to patients suspected of suffering from acute myocardial infarction. These trials were conducted on patients meeting strict entry criteria. In order to assess this therapy when applied to a broader range of myocardial infarction patients, we performed a Phase IV study of metoprolol in acute myocardial infarction. The study was designed to test whether early (less than 8 hours from onset of chest pain) intervention by practicing physicians with open label intravenous metoprolol for cases of suspected acute myocardial infarction achieved mortality results similar to those obtained in large randomized clinical trials. We studied 3824 patients treated by 741 physicians representing a broad spectrum of clinical practice in the United States. Seventy-two percent of the patients entered into the study had confirmed myocardial infarction (39% anterior, 39% inferior, 22% other locations) and 85% of all individuals treated tolerated the full intravenous dose of 15 mg of metoprolol. The 15 day total mortality and cardiovascular mortality rates were 4.9% and 4.5%; 90 day mortality rates were 6.9 and 5.9%. Patients with anterior infarctions had a significantly greater cumulative mortality rate than patients with other types of infarctions. Marked bradycardia (heart rate less than 45 beats per minute) in the first 8 hours post treatment occurred in 4.7% cases and hypotension (systolic blood pressure less than 90 mm Hg) occurred in 9.8% of cases. When compared with the results of the Göteborg and MIAMI trials of metoprolol, it appears that there is no appreciable increase in mortality or morbidity when metoprolol is used in the community practice of acute coronary care.

Analysis of rifampin disk diffusion and stability in 7H10 agar.

Rifampin was incorporated into Middlebrook 7H10 medium either by adding an aliquot of the antibiotic into melted agar (final concentration 1.0 and 3.0 mug/ml) or by submerging a 5 or 15 mug of rifampin paper disk into 5 ml of melted agar contained in one quadrant of a Felson "X" plate. At intervals, plugs of agar were removed from the stored plates and assayed. Plates stored at 5 C for 28 days showed no loss of potency; at 37 C, the half-life of rifampin was 9 days. Stability of rifampin at these concentrations in 7H10 medium was independent of the method used for incorporation. Using the disk method, uniform rifampin concentrations of 0.75 mug/ml on day 5 for the 5-mug disk and 2.7 mug/ml on day 6 for the 15-mug disk were observed. Results indicated that the rifampin concentrations within the agar dilution and disk diffusion plates were equivalent at these times.