The most prominent effect of bisoprolol fumarate tablets is the negative chronotropic effect, resulting in a reduction in resting and exercise heart rate. There is a fall in resting and exercise cardiac output with little observed change in stroke volume, and only a small increase in right atrial pressure, or pulmonary capillary wedge pressure at rest or during exercise.
Findings in short-term clinical hemodynamics studies with bisoprolol fumarate tablets are similar to those observed with other beta-blocking agents.
The mechanism of action of its antihypertensive effects has not been completely established. Factors which may be involved include:
1) Decreased cardiac output,
2) Inhibition of renin release by the kidneys,
3) Diminution of tonic sympathetic outflow from the vasomotor centers in the brain.
In normal volunteers, bisoprolol fumarate tablets therapy resulted in a reduction of exercise- and isoproterenol-induced tachycardia. The maximal effect occurred within 1-4 hours post-dosing. Effects persisted for 24 hours at doses equal to or greater than 5 mg.
Electrophysiology studies in man have demonstrated that bisoprolol fumarate tablets significantly decreases heart rate, increases sinus node recovery time, prolongs AV node refractory periods, and, with rapid atrial stimulation, prolongs AV nodal conduction.
Beta1-selectivity of bisoprolol fumarate tablets has been demonstrated in both animal and human studies. No effects at therapeutic doses on beta2-adrenoceptor density have been observed. Pulmonary function studies have been conducted in healthy volunteers, asthmatics, and patients with chronic obstructive pulmonary disease (COPD). Doses of bisoprolol fumarate tablets ranged from 5 to 60 mg, atenolol from 50 to 200 mg, metoprolol from 100 to 200 mg, and propranolol from 40 to 80 mg. In some studies, slight, asymptomatic increases in airways resistance (AWR) and decreases in forced expiratory volume (FEV1) were observed with doses of bisoprolol fumarate 20 mg and higher, similar to the small increases in AWR also noted with the other cardioselective beta-blockers. The changes induced by beta- blockade with all agents were reversed by bronchodilator therapy.
Bisoprolol fumarate tablets had minimal effect on serum lipids during antihypertensive studies. In U.S. placebo-controlled trials, changes in total cholesterol averaged +0.8% for bisoprolol fumarate-treated patients, and +0.7% for placebo. Changes in triglycerides averaged +19% for bisoprolol fumarate-treated patients, and +17% for placebo.
Bisoprolol fumarate tablets have also been given concomitantly with thiazide diuretics. Even very low doses of hydrochlorothiazide (6.25 mg) were found to be additive with bisoprolol fumarate in lowering blood pressure in patients with mild-to-moderate hypertension.