Metoprolol

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[edit] BRAND NAMES

[edit] STRUCTURE

Metoprolol.jpg

[edit] MECHANISM OF ACTION

Metoprolol is a β1 selective adrenergic antagonist with no intrinsic sympathomimetic activity, and membrane-stabilizing activity is detectable only at doses much greater than required for beta blockade.

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.

[edit] INDICATIONS

  • Treatment of hypertension to lower blood pressure. Lowering blood pressure reduces the risk of fatal and nonfatal cardiovascular events, primarily strokes and myocardial infarctions.
  • Long-term treatment of angina pectoris.
  • Treatment of hemodynamically stable patients with definite or suspected acute myocardial infarction to reduce cardiovascular mortality.
  • Migraine prophylaxis

[edit] DOSAGE

  • Hypertension: treatment should be initiated with doses of 50 mg twice a day. If an adequate response is not seen after one week, dosage should be increased to 100 mg twice a day. In some cases the daily dosage may need to be increased by further 100 mg increments at intervals of not less than two weeks up to a maximum of 200 mg twice a day, which should not be exceeded. The usual maintenance dose is within the range of 100-200 mg daily.
    When Metoprolol is combined with another antihypertensive agent which is already being administered, it should be added initially at a dose of 50 mg twice a day. After one or two weeks the daily dosage may be increased if required, in increments of 100 mg, at intervals of not less than two weeks, until adequate blood pressure control is obtained.
  • Angina Pectoris: The recommended dosage range is 100-400 mg per day in divided doses. Treatment should be initiated with 50 mg twice a day for the first week. If response is not adequate, the daily dosage should be increased by 100 mg for the next week.
    The usual maintenance dose is 200 mg/day. The need for further increases should be closely monitored at weekly intervals and the dosage increased in 100 mg increments to a maximum of 400 mg/day in two or three divided doses.


  • Acute Myocardial Infarction: In patients with definite or suspected acute myocardial infarction, treatment with metoprolol I.V. Injection should be initiated as soon as possible after the patient's arrival in the hospital and after eligibility is established. Treatment should begin with three bolus injections of 5 mg each at approximately 2 minute intervals

    In patients who tolerate the full intravenous dose (15 mg),metoprolol tablets 50 mg every 6 hours should be initiated 15 minutes after the last intravenous dose and continued for 48 hours. Thereafter, patients should receive a maintenance dosage of 100 mg twice daily.

    Patients who appear not to tolerate the full intravenous dose should be started on either 25 mg or 50 mg every 6 hours (depending on the degree of intolerance) 15 minutes after the last intravenous dose or as soon as their clinical condition allows. In patients with severe intolerance, treatment with Metoprolol should be discontinued.

    Patients with contraindications to treatment during the early phase of myocardial infarction, patients who appear not to tolerate the full early treatment, and patients in whom the physician wishes to delay therapy for any other reason should be started on metoprolol tablets, 100 mg twice daily, as soon as their clinical condition allows. Treatment can begin within 3 to 10 days of the acute event. Therapy should be continued for at least 3 months. Although the efficacy of treatment with metoprolol beyond 6 months has not been conclusively established, data from studies with other β-blockers suggest that the treatment should be continued for 1 to 3 years.

[edit] CONTRAINDICATIONS

  • Known hypersensitivity to Metoprolol
  • Sinus bradycardia (resting heart rate of 60 beats per minute or less)
  • Sick sinus syndrome without a pacemaker
  • Second and third-degree AV block
  • Right ventricular failure secondary to pulmonary hypertension
  • Patients in cardiogenic shock or decompensated heart failure.
  • Severe peripheral arterial circulatory disorders
  • Anesthesia with agents that produce myocardial depression, e.g. ether.
  • The intravenous form is also contraindicated in the presence of asthma and other obstructive respiratory diseases, in patients with a heart rate <45 beats/min, second- and third-degree heart block; significant first-degree heart block (P-R interval ≥0.24 sec); systolic blood pressure <100 mmHg; or moderate-to-severe cardiac failure.

[edit] WARNINGS AND PRECAUTIONS

  • Cardiac Failure : beta blockade may result in further depression of myocardial contractility and precipitate more severe failure.
  • In Patients Without a History of Cardiac Failure Continued depression of the myocardium with beta-blockers can, in some patients, precipitate cardiac failure. At the first signs or symptoms of heart failure, patients should be fully digitalized and/or given a diuretic and the response observed closely. If cardiac failure continues, despite adequate digitalization and diuretic therapy, Metoprolol therapy should be reduced or withdrawn.
  • Patients with bronchospastic disease (e.g., chronic bronchitis and emphysema): Avoid β-blockers.
  • Diabetes and Hypoglycemia: Beta-blockers may mask some of the manifestations of hypoglycemia, particularly tachycardia.

[edit] INTERACTIONS

[edit] PREGNANCY AND LACTATION

  • Pregnancy Category C (US)
  • Metoprolol is excreted in breast milk in very small quantities. Caution should be exercised when administered to a nursing woman

[edit] SIDE EFFECTS

Most common adverse reactions: tiredness, dizziness, depression, shortness of breath, bradycardia, hypotension, diarrhea and rash.

Beta blockers such as propranolol and metoprolol are more likely than other less lipophilic beta blockers to cause centrally-mediated side effects, such as sleep disturbances (Insomnia), vivid dreams, nightmares and, rarely, hallucinations.

[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)