Interaction of metoprolol with lorazepam and bromazepam.

The interaction between metoprolol and bromazepam and lorazepam was studied in 12 healthy male volunteers aged 21-37 years. Metoprolol had no significant effect on the pharmacokinetics of bromazepam or lorazepam. However, bromazepam AUC was 35% higher in the presence of metoprolol. Bromazepam enhanced the effect of metoprolol on systolic blood pressure but not on diastolic blood pressure or pulse rate. Lorazepam had no effect on either blood pressure or pulse. Metoprolol did not enhance the effect of bromazepam on the psychomotor tests used in this study. Metoprolol caused a small increase in critical flicker fusion threshold with lorazepam but had no effect on the other tests. Lorazepam (2 mg) was more potent than bromazepam (6 mg) in the doses used in this study. The interaction of metoprolol with bromazepam and lorazepam is unlikely to be of clinical significance. No change in dose is necessary when using these drugs together.