Atenolol/Chlorthalidone

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Contents

[edit] BRAND NAMES

[edit] STRUCTURE

[edit] MECHANISM OF ACTION

Atenolol and chlorthalidone have been used singly and concomitantly for the treatment of hypertension. The antihypertensive effects of these agents are additive:

Atenolol is a β1 selective adrenergic antagonist;

β1 receptors are predominantly located in the heart. The blockade of these receptors reduces the ability of the sympathetic nervous system to increase the myocardial contractile force and rate and the result is a decrease in heart rate and blood pressure

β1 receptors are also located in the juxtaglomerular apparatus of the kidney. The blockade of these receptors inhibits the release of renin from the kidney. Decreased circulating plasma renin leads to a decrease in angiotensin II and aldosterone production, causing a decrease in vasoconstriction and a decrease in water retention.

Atenolol has the lowest lipid solubility of this drug class and it does not have intrinsic sympathomimetic properties or membrane-stabilizing activity.

Chlorthalidone is a thiazide diuretic, it acts on the distal convoluted tubule by inhibiting the sodium-chloride symporter. thus, it reduces NaCl reabsorption, leading to a retention of water in the urine. The enhanced delivery of Na+ and water to the cortical collecting tubule and/or the increased flow rate leads to increased secretion and excretion of K+ and H+. Chlorthalidone promotes also Ca++ reabsorption.

[edit] INDICATIONS

Atenolol and chlorthalidone is indicated for the treatment of hypertension, to lower blood pressure. Lowering blood pressure lowers the risk of fatal and non-fatal cardiovascular events, primarily strokes and myocardial infarctions.

[edit] DOSAGE

The initial dose should be one atenolol and chlorthalidone 50 mg-25 mg tablet given once a day. If an optimal response is not achieved, the dosage should be increased to one atenololand chlorthalidone 100 mg-25 mg tablet given once a day.

When necessary, another antihypertensive agentmay be added gradually beginning with 50% of the usual recommended starting dose to avoid an excessive fall in blood pressure.

[edit] CONTRAINDICATIONS

  • Second- or third-degree AV block
  • Sinus bradycardia (resting heart rate of 60 beats per minute or less)
  • Patients in cardiogenic shock or decompensated heart failure
  • History of hypersensitivity to Atenolol, Chlorthalidone, or to sulfonamide derived drugs.
  • Anuria

[edit] WARNINGS AND PRECAUTIONS

  • Patients with bronchospastic disease (e.g., chronic bronchitis and emphysema): Avoid β-blockers. However, if deemed necessary (patients who do not respond to, or cannot tolerate, other antihypertensive treatment), use with caution and at lowest effective dose.
  • Cardiac Failure: Sympathetic stimulation is necessary in supporting circulatory function in congestive heart failure, and beta blockade carries the potential hazard of further depressing myocardial contractility and precipitating more severe failure. IN PATIENTS WITHOUT A HISTORY OF CARDIAC FAILURE, continued depression of the myocardium with beta-blocking agents over a period of time can, in some cases, lead to cardiac failure. At the first sign or symptom of impending cardiac failure, patients should be treated appropriately according to currently recommended guidelines, and the response observed closely. If cardiac failure continues despite adequate treatment, atenolol and chlorthalidone should be withdrawn.
  • Ischemic Heart Disease: Acute exacerbation of coronary artery disease upon cessation of therapy: Severe exacerbation of angina and the occurrence of myocardial infarction and ventricular arrhythmias have been reported in angina patients following the abrupt discontinuation of therapy with beta blockers. Do not abruptly discontinue.
  • Diabetes and Hypoglycemia: Beta blockers may mask some of the manifestations of hypoglycemia, particularly tachycardia. Nonselective beta blockers may potentiate insulin-induced hypoglycemia and delay recovery of serum glucose levels. Because of its beta1-selectivity, this is less likely with Atenolol. However, patients subject to spontaneous hypoglycemia, or diabetic patients receiving insulin or oral hypoglycemic agents, should be cautioned about these possibilities and Atenolol should be used with caution

[edit] INTERACTIONS

  • Concomitant Use of Verapamil or diltiazem type calcium channel blockers: Bradycardia and heart block can occur and the left ventricular end diastolic pressure can rise when beta-blockers are administered with verapamil or diltiazem. Patients with pre­existing conduction abnormalities or left ventricular dysfunction are particularly susceptible
  • Hypotensive agents (e.g., reserpine, MAO inhibitors, clonidine) may increase the risk of hypotension and/or severe bradycardia.
  • Disopyramide is a Type I antiarrhythmic drug with potent negative inotropic and chronotropic effects. Disopyramide has been associated with severe bradycardia, asystole and heart failure when administered with beta blockers.
  • Amiodarone is an antiarrhythmic agent with negative chronotropic properties that may be additive to those seen with beta blockers.
  • Both digitalis glycosides (Digoxin) and beta blockers slow atrioventricular conduction and decrease heart rate. Concomitant use can increase the risk of bradycardia.

[edit] PREGNANCY AND LACTATION

  • Pregnancy Category D (US)
  • Nursing Mothers: Atenolol is excreted in human breast milk at a ratio of 1.5 to 6.8 when compared to the concentration in plasma. Caution should be exercised when Atenolol is administered to a nursing woman. Clinically significant bradycardia has been reported in breast-fed infants. Premature infants, or infants with impaired renal function, may be more likely to develop adverse effects.

[edit] SIDE EFFECTS

[edit] RELATED LINKS

[edit] BIBLIOGRAPHY

[edit] REFERENCES

Antihypertensives
ACE inhibitors Benazepril (Lotensin)   Captopril (Capoten)   Cilazapril   Delapril   Enalapril (Renitec, Vasotec)   Fosinopril (Monopril)  Lisinopril (Prinivil, Zestril)   Moexipril (Univasc)  Perindopril (Aceon)  Quinapril (Accupril)  Ramipril (Altace, Triatec)   Trandolapril (Mavik)  Zofenopril (Bifril, Zopranol)
Angiotensin II receptor antagonist Azilsartan (Edarbi)   Candesartan (Atacand)   Eprosartan (Teveten)   Irbesartan (Aprovel, Avapro, Karvea)   Losartan (Cozaar)   Olmesartan (Benicar, Olmetec)   Telmisartan (Micadis)   Valsartan (Diovan, Tareg)
Renin inhibitors Aliskiren (Rasilez, Tekturna)
Alpha-1 blockers Doxazosin (Cardura)   Prazosin (Minipress)   Terazosin (Hytrin)
Alpha-2 agonists (centrally acting) Clonidine (Oral route)   Clonidine (Transdermal) (Catapresan)   Guanfacine (Tenex)   Methyldopa (Aldomet)
Calcium channel blockers Dihydropyridines‎ Amlodipine (Norvasc)   Barnidipine (Vasexten)   Felodipine (Plendil)   Isradipine (Dynacirc)   Lacidipine (Lacipil, Motens)   Lercanidipine (Zanidip)   Manidipine   Nicardipine   Nifedipine (Adalat)   Nisoldipine   Nitrendipine
Benzothiazepine‎ Diltiazem (Cardizem, Taztia XT, Tiazac, Tildiem)
Phenylalkylamine‎ Gallopamil   Verapamil (Calan)
Beta blockers Beta1 selective (cardioselective) Acebutolol (Sectral)   Atenolol (Tenormin)   Betaxolol (Kerlon)   Bisoprolol (Concor)   Celiprolol (Cordiax)   Metoprolol (Betaloc, Lopressor, Toprol-XL)   Nebivolol (Bystolic, Lobivon, Nebilox)
Nonselective (Beta1 and Beta2 blockers) Oxprenolol (Trasitensin)   Propranolol (Inderal)   Timolol (Blocadren)
Nonselective (Beta1, Beta2 and Alpha1 blockers) Carvedilol (Dilatrend)   Labetalol (Trandate)
Beta blocker with intrinsic sympathomimetic activity (ISA) Acebutolol (Sectral)   Celiprolol (Cordiax)
Lipophilic Beta blockers Propranolol (Inderal)   Metoprolol (Betaloc, Lopressor, Toprol-XL)   Oxprenolol (Trasitensin)
Diuretics Carbonic anhydrase inhibitors Acetazolamide (Diamox)
Loop diuretics Bumetanide   Etacrynic acid   Furosemide (Lasix)   Piretanide   Torasemide (Demadex)
Thiazide diuretics Chlorothiazide (Diuril)   Hydrochlorothiazide (Esidrex)
Thiazide-like diuretics Chlortalidone (Hygroton)   Indapamide (Lozol, Lozide)   Metolazone
Potassium-sparing diuretics Epithelial sodium channel blockers: Amiloride (Midamor)   Triamterene (Dyrenium)
Aldosterone receptor antagonists: Potassium canrenoate   Eplerenone (Inspra)   Spironolactone (Aldactone)
Osmotic diuretics Mannitol
Combination therapy Amiloride/Hydrochlorothiazide (Moduretic)   Spironolactone/Hydrochlorothiazide (Aldactazide)