Clinical pharmacology of two specific bradycardiac agents.

The effect of two i.v.-infusion regimens of falipamil on atropine-induced changes of heart rate and the effect of ULFS 49 Cl in 3 different oral doses during a 7-day medication period were studied in volunteers. Both studies were double-blind, randomized and placebo controlled. Under placebo, low doses of atropine caused a 16% reduction in heart rate, a 1 mg cumulative dose increased heart rate by 23%. 100 mg falipamil was followed by a 9% reduction in heart rate. Low doses of atropine enhanced this decrease to 14%, whereas a 1 mg cumulative dose of atropine increased heart rate by only 3%. Similar results were obtained after administration of 200 mg falipamil. ULFS 49 Cl induced a constant reduction of heart rate at rest and during ergometry without changing systolic and diastolic blood pressure. Because no interrelation was found between efficacy and corresponding plasma levels of the drug, it can be concluded that the concentration of the drug in the tissue is responsible for efficacy and duration of action. The minimal effective and the therapeutic doses were 3 X 2.5 mg p.o. and 3 X 5 mg p.o. respectively. In contrast to falipamil, which increased the QT-interval by approximately 20%, ULFS 49 Cl did not change QT-time. Side-effects typical for 'specific bradycardic agents', such as coruscation were seen. Peak occurrence was between day 1 and day 4, thereafter a decreasing frequency was observed. In general, both drugs were effective and well tolerated.