Bisoprolol

Bisoprolol is a drug belonging to the group of beta blockers, a class of drugs used primarily in cardiovascular diseases. More specifically, it is a selective type β1adrenergic receptor blocker. The FDA approved Duramed Pharmaceutical's application for Zebeta Oral Tablets (Bisoprolol Fumarate) as a new molecular entity on July 31, 1992. It has since been approved by the FDA for manufacture by Teva, Mylan, Sandoz, and Mutual Pharmaceutical Company.^[3]

Clinical use

Bisoprolol is beneficial in treatment for: high blood pressure (hypertension), reduced blood flow to the heart (cardiac ischemia); preventative treatment before and primary treatment after heart attacks decreasing the chances of recurrence.^[4] During hypertension there is an elevated blood pressure, which is what Bisoprolol targets.^[5][6]While in cardiac ischemia the drug is used to reduce the activity of the heart muscle and therefore reduce oxygen and nutrient demand, so reduced blood supply can still transport sufficient amounts of oxygen and nutrients. [24][27][30]

Many beta-blockers are now available and in general they are all equally effective. There are, however, differences between them which may affect choice in treating particular diseases or individual patients.

Beta-blockers with a relatively short duration of action have to be given two or three times daily. Many of these are, however, available in modified-release formulations so that administration once daily is adequate for hypertension. For angina twice-daily treatment may sometimes be needed even with a modified-release formulation. Some beta-blockers such as atenolol, bisoprolol, carvedilol, celiprolol, and nadolol have an intrinsically longer duration of action and need to be given only once daily.

Mechanism of action

Bisoprolol is cardioprotective because it selectively and competitively blocks catecholamine (adrenalin) stimulation of beta-1 adrenergic receptors (β1 adrenoreceptor) mainly found in the heart muscle cells and heart conduction tissue (cardio specific) but also found in juxtaglomerular cells in the kidney [24]. Normally adrenalin and noradrenalin stimulation of the β1 adrenoreceptor activates a signalling cascade (Gs protein and cAMP) which ultimately lead to increased contractility and increased heart rate of the heart muscle and heart pacemaker respectively [23]. Bisoprolol competitively blocks the activation of this cascade and therefore decreases the adrenergic tone/stimulation of the heart muscle and pacemaker cells. Decreased adrenergic tone shows less contractility of heart muscle and lowered heart rate of heart pacemaker [25][28][29].

These are the favourable factors that are decreased and treat hypertension, heart attacks and ischemia. The decreases in contractility and heart rate are beneficial for hypertension because they reduce blood pressure^[5][27] but for preventive measures for heart attacks and cardiac ischemia these decreases in heart rate and contraction decrease the hearts demand for oxygen and nutrients; primary treatment post heart attacks is to prevent recurrence of the infarction [27][30]^[6].

Cautions

Beta-blockers can precipitate asthma and this effect can be dangerous. Beta-blockers should be avoided in patients with a history of asthma or bronchospasm; if there is no alternative, a cardioselective beta-blocker can be used with extreme caution under specialist supervision. Atenolol, bisoprolol, metoprolol, nebivolol, and (to a lesser extent) acebutolol, have less effect on the beta2 (bronchial) receptors and are, therefore, relatively cardioselective, but they are not cardiospecific. They have a lesser effect on airways resistance but are not free of this side effect.

Side effects

Overdose of bisoprolol leads to fatigue, hypotension[27], low blood sugar [29], bronchospasms and bradycardia [27]. Bronchospasms and low blood sugar because at high doses drug can be an antagonist for β2 adrenergic receptors located in lung and in liver. Bronchspasm due to blockage in lungs of β2 receptor and low blood sugar because of decreased stimulation of glycogenolysis and gluconeogenesis in the liver via β2 receptor.

Dose:5-10mg once in a day