Cardioprotective action: The mechanism whereby atenolol improves survival in patients with MI is unknown. However, it does reduce the frequency of PVCs, chest pain, and enzyme elevation. Metabolism: Metabolized minimally. In patients with normal renal function, plasma half-life is 6 to 7 hours; half-life increases as renal function decreases.
Contraindications and precautions Contraindicated in patients with sinus bradycardia, greater than first-degree heart block, overt cardiac failure, or cardiogenic shock.
Use cautiously in patients at risk for heart failure and in those with bronchospastic disease, diabetes, and hyperthyroidism. Interactions Drug-drug.
Monitor patient for effect. Antihypertensives: May potentiate antihypertensive effect of these drugs. Monitor blood pressure.
Insulin, oral hypoglycemics: Alters dosage requirements in stable diabetic patients. Monitor serum glucose level. Adverse reactions CNS: fatigue, lethargy, vertigo, drowsiness, dizziness, mental depression, fever. CV: bradycardia, hypotension, heart failure, intermittent claudication, changes in exercise tolerance and ECG.
GI: nausea, diarrhea, dry mouth. Lipid insoluble hydrophilic compounds atenolol, sotalol, nadolol are excreted only by the kidneys and have low brain penetration. Metoprolol and propranolol are more lipophilic compounds and so are more often used in migraine and have more cerebral side effects of b-blockers. Peak blood levels are reached between two and four hours after ingestion.
Unlike propranolol or metoprolol, atenolol undergoes little or no metabolism by the liver and the absorbed portion is eliminated by renal excretion.
The elimination half-life of atenolol is 6 to 7 hours and there is no alteration of kinetic profile of drug by chronic administration. Following intravenous administration peak plasma levels are reached within 5 minutes. Declines from peak levels are rapid 5 to 10 fold during the first 7 hours. Following oral doses of 50 mg or mg both b-blocking and anti-hypertensive effects persist for at least 24 hours. Atenolol 2nd generation b-blocker is a b1 selective antagonist cardio selective ; however this selectivity is not absolute and at higher doses atenolol inhibits b-2 Adrenoceptors chiefly located in bronchial and vascular musculature.
It has no partial agonist and intrinsic sympathomimetic activity and so results in disturbances in lipid profile unlike acebutolol. CVS: The major therapeutic effects are on cardiovascular system Table 2. It is important to distinguish these effects in normal subjects from those in subjects with cardiovascular disease CVD such as hypertension or myocardial ischemia.
The negative ionotropic and chronotropic effects are modest when simulation of b-receptors is low. However, in presence of activated sympathetic nervous system as during exercise or stress; atenolol attenuates the expected rise in heart rate HR and myocardial contractility. The exercise-induced increase in cardiac output CO is less affected because of an increase in stroke volume. It decreases the effects of catecholamine on determinants of myocardial oxygen consumption heart rate; contractility and systolic pressure , hence improving the relationship between cardiac oxygen supply and demand; exercise tolerance is improved in patients with angina.
The duration of action is dose-related and also bears a linear relationship to the logarithm of plasma atenolol concentration. Besides reducing HR, cardiac index and blood pressure; effects on total peripheral resistance have been documented; though less uniformly. Atenolol blunts the reflex mediated increase in heart rate that usually follows the Valsalva maneuver or abrupt tilting to the upright position. An increase in atrial refractory period follows administration of atenolol and atrioventricular A-V conduction is prolonged.
Besides prolonging AV nodal refractoriness, decrease in intracellular calcium overload and after-depolarization mediated automaticity is seen. The anti-arrhythmic actions of atenolol are less than of sotalol and propranolol due to less membrane stabilizing action. Atenolol has no effect on plasma volume, exchangeable sodium or potassium or total body potassium. Like other b-blocking agents, atenolol inhibits the release of renin,9 inhibits lipolysis and causes increased plasma triglyceride levels and a fall in HDL concentration.
When administrated in large doses enough to block b-2 receptors, the resulting reduction of glucose production in response to catecholamine release can prolong hypoglycemia induced by insulin. Atenolol reduces renal vascular resistance in hypertensive patients9. No effect on creatinine clearance, glomerular filtration rate or renal blood flow has been observed in contrast to non-selective b-blockers.
Although atenolol does not pass the blood brain barrier fully, some of the compound reaches the central nervous system. The initial dose of atenolol for the treatment of hypertension usually is 50 mg per day given once daily. If an adequate therapeutic response is not evident within several weeks, the daily dose may be increased to mg, Higher doses are unlikely to provide any greater anti-hypertensive effect.
Young hypertensives have high renin hypertension and increased sympathetic activity. So b-blockers are used in younger ages only now. In elderly hypertensives b- blockers specially atenolol is no longer a preferred drug. In such patients we should use a and b adrenergic antagonists such as labetalol. Sudden discontinuation of some b adrenergic blockers can produce a withdrawal syndrome that is likely due to up regulation of b receptors during blockade, causing enhanced tissue sensitivity to endogenous catecholamines; this can exacerbate the symptoms of coronary artery disease.
The result, especially in active patients, can be rebound hypertension. Thus, b adrenergic blockers should not be discontinued abruptly except under close observation. The dosage should be tapered over 5 - 10 days prior to discontinuation.
In angina pectoris the initial dose is 50 mg once daily. If an optimal response is not achieved within one week, the dosage should be increased to mg.
Some patients may require a dose of mg. In some patients with acute MI within 6 hours specially those with anterior infarction and sinus tachycardia but not in failure and no history of asthma or left bundle branch block intravenous atenolol may be given. It should be administered under carefully controlled conditions including monitoring of blood pressure, HR and electrocardiogram. In most patients atenolol 50 mg should be initiated on the first day. Thereafter, it can be given orally either 50 mg once or twice a day.
The seven day mortality rate in atenolol group was 3. However, false negative TMT can occur in patients on b-blockers. Conversion of negative or mildly positive TMT into strongly positive result after withdrawal of b-blockers has been reported It's effect on conduction tissue are utilized to control HR in patients of mitral stenosis in sinus rhythm. Make sure you tell your doctor if you have any other medical problems, especially:.
In addition to the use of this medicine, treatment for your high blood pressure may include weight control and changes in the types of foods you eat, especially foods high in sodium.
Your doctor will tell you which of these are most important for you. You should check with your doctor before changing your diet. Many patients who have high blood pressure will not notice any signs of the problem. In fact, many may feel normal. It is very important that you take your medicine exactly as directed and that you keep your appointments with your doctor even if you feel well.
Remember that this medicine will not cure your high blood pressure, but it does help control it. You must continue to take it as directed if you expect to lower your blood pressure and keep it down.
You may have to take high blood pressure medicine for the rest of your life. If high blood pressure is not treated, it can cause serious problems such as heart failure, blood vessel disease, stroke, or kidney disease.
Do not interrupt or stop taking this medicine without first checking with your doctor. Your doctor may want you to gradually reduce the amount you are taking before stopping it completely. Some conditions may become worse when the medicine is stopped suddenly, which can be dangerous.
The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so. The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.
If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses. Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light.
Keep from freezing. It is very important that your doctor check your progress at regular visits to make sure this medicine is working properly and to check for unwanted effects. Using this medicine while you are pregnant can harm your unborn baby. Use an effective form of birth control to keep from getting pregnant.
If you think you have become pregnant while using the medicine, tell your doctor right away. Make sure any doctor or dentist who treats you knows that you are using this medicine.
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