Tenbloka-100 ( Atenolol 100mg)
Pharmacotherapeutic group: Beta-blocking agents, plain, selective. ATC code: CO7A B03.
Atenolol is a beta-blocker, which is beta1-selective, (i.e. acts preferentially on beta1-adrenergic receptors in the heart). Selectivity decreases with increasing dose.
Atenolol is without intrinsic sympathomimetic and membrane-stabilising activities and as with other beta-blockers, has negative inotropic effects (and is therefore contraindicated in uncontrolled heart failure).
As with other beta-blockers, the mode of action of atenolol in the treatment of hypertension is unclear. It is probably the action of atenolol in reducing cardiac rate and contractility, which makes it effective in eliminating, or reducing the symptoms of patients with angina.
It is unlikely that any additional ancillary properties possessed by S (-) atenolol, in comparison with the racemic mixture, will give rise to different therapeutic effects.
- Management of hypertension.
- Management of angina pectoris.
- Management of cardiac dysrhythmias.
- Management of myocardial infarction. Early intervention in the acute phase and long term prophylaxis after recovery from myocardial infarction
Posology and method of administration
Method of administration: Oral
The dose must always be adjusted to individual requirements of the patients, with the lowest possible starting dosage. The following are guidelines:
Hypertension : One tablet daily. Most patients respond to 100 mg daily given orally as a single dose. Some patients, however, will respond to 50 mg given as a single daily dose. The effect will be fully established after one to two weeks. A further reduction in blood pressure may be achieved by combining Atenolol tablets with other antihypertensive agents. For example, co-administration of Atenolol tablets with a diuretic provides a highly effective and convenient antihypertensive therapy.
Angina : Most patients with angina pectoris will respond to 100 mg given orally once daily or 50 mg given twice daily. It is unlikely that additional benefit will be gained by increasing the dose.
Cardiac arrhythmias : Having controlled the dysrhythmias with intravenous atenolol a suitable maintenance dosage is 50 mg – 100 mg daily, given as single dose.
Myocardial infarction : For patients suitable for treatment with intravenous beta-blockade and presenting within 12 hours of the onset of chest pain, Atenolol 5–10 mg should be given by slow intravenous injection (1 mg/minute) followed by Atenolol 50 mg orally about 15 minutes later, provided no untoward effects have occurred from the intravenous dose. This should be followed by a further 50 mg orally 12 hours after the intravenous dose, and then 12 hours later by 100 mg orally, once daily. If bradycardia and/or hypotension requiring treatment, or any other untoward effects occur, Atenolol should be discontinued.
Paediatric population: There is no paediatric experience with Atenolol and for this reason it is not recommended for use in children.
Renal failure: Since Atenolol is excreted via the kidneys, the dosage should be adjusted in cases of severe impairment of renal function.
No significant accumulation of Atenolol occurs in patients who have a creatinine clearance greater than 35 ml/min/1.73 m2 (normal range is 100–150 ml/min/1.73 m2).
For patients with a creatinine clearance of 15–35 ml/min/1.73 m2 (equivalent to serum creatinine of 300–600 micromol/litre), the oral dose should be 50 mg daily and the intravenous dose should be 10 mg once every two days.
For patients with a creatinine clearance of less than 15 ml/min/1.73 m2 (equivalent to serum creatinine of greater than 600 micromol/litre), the oral dose should be 25 mg daily or 50 mg on alternate days and the intravenous dose should be 10 mg once every four days.
Patients on haemodialysis should be given 50 mg orally after each dialysis; this should be done under hospital supervision as marked falls in blood pressure can occur.
Atenolol, as with other beta-blockers, should not be used in patients with any of the following:
- Cardiogenic shock
- Uncontrolled heart failure
- Sick sinus syndrome (including sino-atrial block)
- Second-or third-degree heart block
- Untreated phaeochromocytoma
- Metabolic acidosis
- Bradycardia (< 50 bpm before treatment initiation)
- Known hypersensitivity to the active substance, or any of the excipients
- Severe peripheral arterial circulatory disturbances
- Severe asthma and severe chronic obstructive pulmonary disorders, such as airway obstructions
- The intravenous application of calcium channel blockers (verapamil / diltiazem type) is contraindicated in patients who use atenolol (except in intensive care unit).
Warnings and precautions for use
Atenolol as with other beta-blockers:
Should not be withdrawn abruptly. The dosage should be withdrawn gradually over a period of 7–14 days, to facilitate a reduction in beta-blocker dosage. Patients should be followed during withdrawal, especially those with ischaemic heart disease. Furthermore there is a risk on myocardial infarction and sudden death.
When a patient is scheduled for surgery, and a decision is made to discontinue beta-blocker therapy, this should be done at least 24 hours prior to the procedure. Continuation of beta-blockade reduces the risk of arrhythmias during induction and intubation, however the risk of hypotension may be increased as well. The risk-benefit assessment of stopping beta-blockade should be made for each patient. If treatment is continued, an anaesthetic with little negative inotropic activity should be selected to minimise the risk of myocardial depression. The patient may be protected against vagal reactions by intravenous administration of atropine.
Although contraindicated in uncontrolled heart failure (see section 4.3), may be used in patients whose signs of heart failure have been controlled. Caution must be exercised in patients whose cardiac reserve is poor.
May increase the number and duration of angina attacks in patients with Prinzmetal’s angina due to unopposed alpha-receptor mediated coronary artery vasoconstriction. Atenolol is a beta1-selective beta-blocker; consequently, its use may be considered although utmost caution must be exercised.
Although contraindicated in severe peripheral arterial circulatory disturbances, may also aggravate less severe peripheral arterial circulatory disturbances (Raynaud’s disease or syndrome, intermittent claudication).
Due to its negative effect on conduction time, caution must be exercised if it is given to patients with first-degree heart block.
May mask the symptoms of hypoglycaemia, in particular, tachycardia. Insulin sensitivity may be reduced in patients treated with atenolol.
May mask the signs of thyrotoxicosis.
Will reduce heart rate as a result of its pharmacological action. In the rare instances when a treated patient develops symptoms, which may be attributable to a slow heart rate and the pulse rate drops to less than 50–55 bpm at rest, the dose should be reduced.
May cause a more severe reaction to a variety of allergens when given to patients with a history of anaphylactic reaction to such allergens. Such patients may be unresponsive to the usual doses of adrenaline (epinephrine) used to treat the allergic reactions.
May cause a hypersensitivity reaction including angioedema and urticaria.
Should be used with caution in the elderly, starting with a lesser dose
Since Atenolol is excreted via the kidneys, dosage should be reduced in patients with a creatinine clearance of below 35 ml/min/1.73 m2.
Although cardioselective (beta1) beta-blockers may have less effect on lung function than non-selective beta-blockers, as with all beta-blockers, these should be avoided in patients with reversible obstructive airways disease, unless there are compelling clinical reasons for their use. Where such reasons exist, Atenolol may be used with caution. Occasionally, some increase in airways resistance may occur in asthmatic patients however, and this may usually be reversed by commonly used dosage of bronchodilators such as salbutamol or isoprenaline. The label and patient information leaflet for this product state the following warning: “If you have ever had asthma or wheezing, you should not take this medicine unless you have discussed these symptoms with the prescribing doctor”.
As with other beta-blockers, in patients with a phaeochromocytoma, an alpha-blocker should be given concomitantly.
Patients with anamnestically known psoriasis should take atenolol only after careful consideration.
Interaction with other medicinal products and other forms of interaction
Combined use of beta-blockers and calcium channel blockers with negative inotropic effects, e.g. verapamil and diltiazem, can lead to an exaggeration of these effects particularly in patients with impaired ventricular function and/or sinoatrial or atrioventricular conduction abnormalities. This may result in severe hypotension, bradycardia and cardiac failure. Neither the beta-blocker nor the calcium channel blocker should be administered intravenously within 48 hours of discontinuing the other.
Concomitant therapy with dihydropyridines, e.g. nifedipine, may increase the risk of hypotension, and cardiac failure may occur in patients with latent cardiac insufficiency.
Digitalis glycosides, in association with beta-blockers, may increase atrioventricular conduction time.
Beta-blockers may exacerbate the rebound hypertension, which can follow the withdrawal of clonidine. If the two drugs are co-administered, the beta-blocker should be withdrawn several days before discontinuing clonidine. If replacing clonidine by beta-blocker therapy, the introduction of beta-blockers should be delayed for several days after clonidine administration has stopped. (See also prescribing information for clonidine.)
Caution must be exercised when prescribing a beta-blocker with Class I antiarrhythmic agents such as disopyramide, and quinidine which may have potentiating effect on atrial-conduction time and induce a negative inotropic effect.
Concomitant use of sympathomimetic agents, e.g. adrenaline (epinephrine), may counteract the effect of beta-blockeuropeers.
Concomitant use with insulin and oral antidiabetic drugs may lead to the intensification of the blood sugar lowering effects of these drugs. Symptoms of hypoglycaemia, particularly tachycardia, may be masked.
Concomitant use of prostaglandin synthetase-inhibiting drugs, e.g. ibuprofen and indomethacin, may decrease the hypotensive effects of beta-blockers.
Caution must be exercised when using anaesthetic agents with Atenolol. The anaesthetist should be informed and the choice of anaesthetic should be an agent with as little negative inotropic activity as possible. Use of beta-blockers with anaesthetic drugs may result in attenuation of the reflex tachycardia and increase the risk of hypotension. Anaesthetic agents causing myocardial depression such as cyclopropane and trichlorethylene, lidocaine, procainamide and beta-adrenoceptor stimulants such as noradrenaline (norepinephrine) are best avoided.
Not recommended association with monoamineoxidase inhibitors (except MAO-B inhibitors)
Not recommended association with Baclofen: Causes an increased antihypertensive activity.
Not recommended association with contrast media, iodinated: Atenolol may impede the compensatory cardiovascular reactions associated with hypotension or shock induced by iodinated contrast products.
Amiodarone: Combination with atenolol may result in additive depressant effects on conduction and negative inotropic effects, especially in patients with underlying sinus node dysfunction or atrioventricular node dysfunction.
Ampicillin: May reduce the bioavailability of atenolol. Therefore the physician should watch for evidence of altered atenolol response especially when large doses of ampicillin are administered concomitantly
Peripheral muscle relaxants (e.g. Suxamethonium halogenide, Tubocurarine): concomitant use of atenolol could increase and extent the relaxative effect of muscle relaxants.
Fertility, pregnancy and lactation
Caution should be exercised when Atenolol tablets is administered during pregnancy or to a woman who is breast-feeding.
Pregnancy: Atenolol crosses the placental barrier and appears in the cord blood. No studies have been performed on the use of Atenolol in the first trimester and the possibility of foetal injury cannot be excluded. Atenolol has been used under close supervision for the treatment of hypertension in the third trimester. Administration of Atenolol to pregnant women in the management of mild to moderate hypertension has been associated with intra-uterine growth retardation.
The use of Atenolol in women who are, or may become, pregnant requires that the anticipated benefit be weighed against the possible risks, particularly in the first and second trimesters, since beta-blockers, in general, have been associated with a decrease in placental perfusion which may result in intra-uterine deaths, immature and premature deliveries.
Breast-feeding: There is significant accumulation of Atenolol in breast milk.
Neonates born to mothers who are receiving Atenolol at parturition or breast-feeding may be at risk of hypoglycaemia and bradycardia.
Effects on ability to drive and use machines
Use is unlikely to result in any impairment of the ability of patients to drive or operate machinery. However, it should be taken into account that occasionally dizziness or fatigue may occur.
The symptoms of overdosage may include bradycardia, hypotension, acute cardiac insufficiency and bronchospasm.
General treatment should include: close supervision; treatment in an intensive care ward; the use of gastric lavage; activated charcoal and a laxative to prevent absorption of any drug still present in the gastrointestinal tract; the use of plasma or plasma substitutes to treat hypotension and shock. The possible uses of haemodialysis or haemoperfusion may be considered.
Excessive bradycardia can be countered with atropine 1–2 mg intravenously and/or a cardiac pacemaker. If necessary, this may be followed by a bolus dose of glucagon 10 mg intravenously. If required, this may be repeated or followed by an intravenous infusion of glucagon 1–10 mg/hour depending on response. If no response to glucagon occurs or if glucagon is unavailable, a beta-adrenoceptor stimulant such as dobutamine 2.5 to 10 micrograms/kg/minute by intravenous infusion may be given.
Dobutamine, because of its positive inotropic effect could also be used to treat hypotension and acute cardiac insufficiency. It is likely that these doses would be inadequate to reverse the cardiac effects of beta-blocker blockade if a large overdose has been taken. The dose of dobutamine should therefore be increased if necessary to achieve the required response according to the clinical condition of the patient.
Bronchospasm can usually be reversed by bronchodilators.