"What are beta blockers and how do they work?
Beta blockers, also known as beta-adrenergic blocking agents, are a class of drugs that works by blocking the neurotransmitters norepinephrine and epinephrine from binding to receptors. "...
Zebeta (bisoprolol fumarate) is a beta1-selective (cardioselective) adrenoceptor blocking agent without significant membrane stabilizing activity or intrinsic sympathomimetic activity in its therapeutic dosage range. Cardioselectivity is not absolute, however, and at higher doses ( ≥ 20 mg) bisoprolol fumarate also inhibits beta2-adrenoceptors, chiefly located in the bronchial and vascular musculature; to retain selectivity it is therefore important to use the lowest effective dose.
Pharmacokinetics and Metabolism
The absolute bioavailability after a 10 mg oral dose of bisoprolol fumarate is about 80%. Absorption is not affected by the presence of food. The first pass metabolism of bisoprolol fumarate is about 20%.
Binding to serum proteins is approximately 30%. Peak plasma concentrations occur within 2-4 hours of dosing with 5 to 20 mg, and mean peak values range from 16 ng/mL at 5 mg to 70 ng/mL at 20 mg. Once daily dosing with bisoprolol fumarate results in less than twofold intersubject variation in peak plasma levels. The plasma elimination half-life is 9-12 hours and is slightly longer in elderly patients, in part because of decreased renal function in that population. Steady state is attained within 5 days of once daily dosing. In both young and elderly populations, plasma accumulation is low; the accumulation factor ranges from 1.1 to 1.3, and is what would be expected from the first order kinetics and once daily dosing. Plasma concentrations are proportional to the administered dose in the range of 5 to 20 mg. Pharmacokinetic characteristics of the two enantiomers are similar.
Bisoprolol fumarate is eliminated equally by renal and non-renal pathways with about 50% of the dose appearing unchanged in the urine and the remainder appearing in the form of inactive metabolites. In humans, the known metabolites are labile or have no known pharmacologic activity. Less than 2% of the dose is excreted in the feces. Bisoprolol fumarate is not metabolized by cytochrome P450 II D6 (debrisoquin hydroxylase).
In subjects with creatinine clearance less than 40 mL/min, the plasma half-life is increased approximately threefold compared to healthy subjects.
In patients with cirrhosis of the liver, the elimination of Zebeta (bisoprolol fumarate) (bisoprolol fumarate) is more variable in rate and significantly slower than that in healthy subjects, with plasma half-life ranging from 8.3 to 21.7 hours.
The most prominent effect of Zebeta (bisoprolol fumarate) 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 Zebeta (bisoprolol fumarate) 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:
- Decreased cardiac output,
- Inhibition of renin release by the kidneys,
- Diminution of tonic sympathetic outflow from the vasomotor centers in the brain.
In normal volunteers, Zebeta (bisoprolol fumarate) 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 Zebeta (bisoprolol fumarate) 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 Zebeta (bisoprolol fumarate) 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 Zebeta (bisoprolol fumarate) 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.
Zebeta (bisoprolol fumarate) 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.
Zebeta (bisoprolol fumarate) has 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.
In two randomized double-blind placebo-controlled trials conducted in the U.S., reductions in systolic and diastolic blood pressure and heart rate 24 hours after dosing in patients with mild-to-moderate hypertension are shown below. In both studies, mean systolic/diastolic blood pressures at baseline were approximately 150/100 mm Hg, and mean heart rate was 76 bpm. Drug effect is calculated by subtracting the placebo effect from the overall change in blood pressure and heart rate.
Sitting Systolic/Diastolic Pressure (BP) and Heart Rate (HR)
Mean Decrease (D) After 3 to 4 Weeks
|Study A||Bisoprolol Fumarate|
|Placebo||5 mg||10 mg||20 mg|
|Total BP (mm Hg)||5.4/3.2||10.4/8.0||11.2/10.9||12.8/11.9|
|Total HR (bpm)||0.5||7.2||8.7||11.3|
|Study B||Bisoprolol Fumarate|
|Placebo||2.5 mg||10 mg|
|Total BP (mm Hg)||3.0/3.7||7.6/8.1||13.5/11.2|
|Total HR (bpm)||1.6||3.8||10.7|
|a Observed total change from baseline minus placebo.|
Blood pressure responses were seen within one week of treatment and changed little thereafter. They were sustained for 12 weeks and for over a year in studies of longer duration. Blood pressure returned to baseline when bisoprolol fumarate was tapered over two weeks in a long-term study.
Overall, significantly greater blood pressure reductions were observed on bisoprolol fumarate than on placebo regardless of race, age, or gender. There were no significant differences in response between black and nonblack patients.
Last reviewed on RxList: 3/29/2011
This monograph has been modified to include the generic and brand name in many instances.
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