Atenolol 50mg/5ml oral suspension

Atenolol is a cardio-selective beta-blocker and as such exerts most of its effects on the heart.[label] It acts as an antagonist to sympathetic innervation and prevents increases in heart rate, electrical conductivity, and contractility in the heart due to increased release of norepinephrine from the peripheral nervous system.[label,T116,A178258] Together the decreases in contractility and rate produce a reduction in cardiac output resulting in a compensatory increase in peripheral vascular resistance in the short-term. This response later declines to baseline with long-term use of atenolol. More importantly, this reduction in the work demanded of the myocardium also reduces oxygen demand which provides therapeutic benefit by reducing the mismatch of oxygen supply and demand in settings where coronary blood flow is limited, such as in coronary atherosclerosis. Reducing oxygen demand, particularly due to exercise, can reduce the frequency of angina pectoris symptoms and potentially improve survival of the remaining myocardium after myocardial infarction. The decrease in rate of sinoatrial node potentials, electrical conduction, slowing of potentials traveling through the atrioventricular node, and reduced frequency of ectopic potentials due to blockade of adrenergic beta receptors has led to benefit in arrhythmic conditions such as atrial fibrillation by controlling the rate of action potential generation and allowing for more effective coordinated contractions. Since a degree of sympathetic activity is necessary to maintain cardiac function, the reduced contractility induced by atenolol may precipitate or worsen heart failure, especially during volume overload.[label]

The effects of atenolol on blood pressure have been established, although it is less effective than alternative beta-blockers, but the mechanism has not yet been characterized.[label,T116] As a β1 selective drug, it does not act via the vasodilation produced by non-selective agents.T116 Despite this there is a sustained reduction in peripheral vascular resistance, and consequently blood pressure, alongside a decrease in cardiac output. It is thought that atenolol's antihypertensive activity may be related to action on the central nervous system (CNS) or it's inhibition of the renin-aldosterone-angiotensin system rather than direct effects on the vasculature.[label]

Atenolol produces CNS effects similar to other beta-blockers, but does so to a lesser extent due to reduces ability to cross the blood-brain barrier.T116 It has the potential to produce fatigue, depression, and sleep disturbances such as nightmares or insomnia.[label,T116] The exact mechanisms behind these have not been characterized but their occurrence must be considered as they represent clinically relevant adverse effects.

Atenolol exerts some effects on the respiratory system although to a much lesser extent than non-selective beta-blockers.[label] Interaction with β2 receptors in the airways can produce bronchoconstriction by blocking the relaxation of bronchial smooth muscle mediated by the sympathetic nervous system.T116 The same action can interfere with β-agonist therapies used in asthma and chronic obstructive pulmonary disease.[label,A178258,T116]

Unlike some other beta-blocker drugs, atenolol does not have intrinsic sympathomimetic or membrane stabilizing activity nor does it produce changes in glycemic control.[label]