Lack of Pharmacodynamic Interactions Between Acute Dose Flosequinan and Xamoterol. A Pilot Study in Healthy Subjects

The possible cardiovascular pharmacodynamic interactions at rest and during exercise of combining oral flosequinan (100 mg) with xamoterol (200 mg) was investigated in a four-way randomised double-blind placebo-controlled crossover trial in eight healthy male volunteers. Xamoterol was better tolerated than flosequinan. The most common adverse events were mild to moderate headache and facial flushing. One volunteer developed headache and vomiting following flosequinan treatment and was replaced. Compared to placebo, at supine rest, flosequinan significantly increased heart rate (HR) by 5 beats.min-1, but had no effect on cardiac output (CO), stroke volume (SV) and mean blood pressure (MBP). Xamoterol significantly increased CO by 1.5 l.min-1, HR (5 beats.min-1) and MBP (6 mmHg) but not SV. The combined treatment (flosequinan + xamoterol) significantly increased CO (1.7 l.min-1) and HR (10 beats.min-1), but had no effect on SV and MBP. During exercise, flosequinan had no significant effect on any variable compared to placebo. Both xamoterol and combined treatment reduced the increase in CO (-4.6 l.min-1 after xamoterol and -3.4 l.min-1 after combined treatment vs. 0.1 l.min-1 after placebo), but had no effect on other variables. The effect of the combined treatment on each haemodynamic variable were no more than the anticipated additive effects of the two drugs. Thus, no cardiovascular pharmacodynamic interaction was found between flosequinan and xamoterol in healthy volunteers.