Metoprolol

Metoprolol (Lopressor®)

Class:
  • Beta-adrenergic blocking agent (Antidysrhythmic Drug Class II)
Actions:
  • Primarily blocks β1 adrenergic receptors on the myocardium (negative chronotropic and negative inotropic agent)
  • Blocks β2 receptors of bronchi and blood  vessels at higher doses
Indications:
  • Acute coronary syndrome/myocardial infarction–decreases oxygen demand of the myocardium
  • Supraventricular tachycardias (PSVT, atrial fibrillation, atrial flutter) [second line drug following adenosine]
  • Left ventricular heart failure (better long term management with lower doses)
  • Hypertension
Pharmacokinetics:
  • Onset: 15 minutes
  • Peak:  1.5 hours (oral); 20 minutes (IV)
  • Half-Life: 3-4 hours minutes
Adverse Effects:
  • Bradycardia, palpitation, cold extremities, Raynaud's phenomenon, intermittent claudication, intensification of AV blocks, heart failure
  • Dizziness, fatigue, insomnia
  • Heartburn, nausea, headache
  • Laryngospasms, respiratory distress, bronchospasms
Signs of Toxicity:
  • Hypotension
  • Bradycardia
  • Bronchospasms or laryngospasms
Contraindications:
  • Bronchospastic diseases (e.g., asthma)
  • Cardiogenic shock
  • Right ventricular heart failure secondary to pulmonary hypertension
  • 2nd or 3rd degree heart block
  • Sinus bradycardia
  • Safety during pregnancy, lactation or with children not established (Category C).
Dosages & Routes:
  • PO: 100 – 200 mg daily in 2 divided doses
  • IV bolus:  5 mg slow IVP at 5-minute intervals until total dose of 15 mg
Nursing Implications:
  • Drug Interactions:  1) Antagonist to beta adrenergic agents; 2) Barbiturates and rifampin may inhibit effects of metoprolol; 3) effects of metoprolol potentiated by cimetidine, methimazole, propylthiouracil, and oral contraceptives; 4) additive bradycardia with digoxin; 5) combination with calcium channel blockers (especially verapamil) may result in heart failure, hypotension, or bradycardia.
  • Drug Incompatibilities:  amphotericin B
  • Monitor blood pressure and apical pulse prior to administration.
  • Cardiac monitor should be used on patients receiving metoprolol IV boluses.

 

References:

American Heart Association. (2006). Handbook of Emergency Cardiac Care (p. 47). Salem, MA: AHA.

Dirks, J.L. (2010) Cardiovascular therapeutic management.  In L.D. Urden, K.M. Stacy, & M.E. Lough's (Eds.) Critical care nursing: Diagnosis and management (6th ed., p. 550).  St. Louis: Mosby Elsevier.

Lehne, R.A. (2010). Pharmacology for nursing care (7th ed., pp. 172-173, 521, 621).  St. Louis: Saunders Elsevier.

Wilson, B.A., Shannon, M.T., Shields, K.M., & Stang, C.L. (2007).  Prentice Hall Nurse's Drug Guide 2007 (pp. 1070-1073).  Upper Saddle River, NJ: Pearson Prentice Hall.

 

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