Nurses Compass
Drug Guide
Metoprolol Fumarate
Classification
Therapeutic: Cardiovascular agent, Beta-blocker
Pharmacological: Beta-adrenergic antagonist
FDA Approved Indications
- Hypertension
- Angina pectoris
- Below-the-knee ischemia (off-label use in some cases)
- Myocardial infarction (post-MI) prophylaxis
Mechanism of Action
Metoprolol selectively blocks beta-1 adrenergic receptors in the heart, reducing heart rate, myocardial contractility, and cardiac output, which lowers blood pressure and oxygen demand.
Dosage and Administration
Adult: Initially 25-50 mg once daily; may be titrated up to 200 mg/day in divided doses based on response.
Pediatric: Not typically recommended for children; dose determined on a case-by-case basis under specialist supervision.
Geriatric: Start at lower doses due to increased sensitivity and potential for adverse effects; gradual titration advised.
Renal Impairment: Use with caution; monitor renal function and adjust dose if necessary.
Hepatic Impairment: Use with caution; no specific dose adjustment, but liver function should be considered.
Pharmacokinetics
Absorption: Well absorbed with oral bioavailability of approximately 50% due to first-pass metabolism.
Distribution: Widely distributed, approximately 12% bound to plasma proteins.
Metabolism: Extensively metabolized in the liver via cytochrome P450 enzymes (mainly CYP2D6).
Excretion: Excreted primarily in urine as metabolites; small amount unchanged.
Half Life: 3 to 7 hours, slightly longer in elderly or certain patient populations.
Contraindications
- Severe bradycardia
- Heart block greater than first degree without pacemaker
- Decompensated heart failure
- Hypotension
Precautions
- Use with caution in patients with asthma or airway obstruction, diabetes (may mask hypoglycemia symptoms), peripheral vascular disease, or Raynaud's phenomenon.
Adverse Reactions - Common
- Fatigue (Common)
- Dizziness (Common)
- Bradycardia (Common)
- Gastrointestinal discomfort (Common)
Adverse Reactions - Serious
- Severe Bradycardia or Heart Block (Rare)
- Hypotension (Rare)
- Bronchospasm in susceptible individuals (Rare)
- Masking of hypoglycemia symptoms (Rare)
Drug-Drug Interactions
- Other antihypertensives, especially calcium channel blockers like verapamil or diltiazem
- Amiodarone
- Digoxin
- NSAIDs (may reduce antihypertensive effect)
Drug-Food Interactions
- Alcohol (may enhance hypotensive effects)
Drug-Herb Interactions
N/ANursing Implications
Assessment: Monitor BP, HR prior to and during therapy; assess for signs of heart failure or worsening cardiac symptoms.
Diagnoses:
- Risk for decreased cardiac output
- Ineffective tissue perfusion
Implementation: Administer doses as prescribed; monitor vital signs regularly; educate patient on recognizing adverse effects.
Evaluation: Maintain target blood pressure; observe for adverse reactions; adjust dosage if necessary.
Patient/Family Teaching
- Take medication exactly as prescribed.
- Notify healthcare provider if experiencing symptoms like dizziness, slow heartbeat, or signs of heart failure.
- Do not abruptly stop medication without consulting healthcare provider.
- Avoid alcohol and consult with provider before using other medications or supplements.
Special Considerations
Black Box Warnings:
- Potential to cause or exacerbate heart failure; abrupt discontinuation may cause acute tachycardia, hypertension, or ischemia.
Genetic Factors: Metabolism may vary with CYP2D6 polymorphisms affecting drug levels.
Lab Test Interference: May mask hypoglycemia symptoms in diabetic patients.
Overdose Management
Signs/Symptoms: Bradycardia, hypotension, bronchospasm, hypoglycemia, or cardiac arrest.
Treatment: Discontinue medication, administer activated charcoal if ingestion was recent, support vital signs, and administer Atropine for bradycardia, vasopressors for hypotension, or intravenous fluids as needed.
Storage and Handling
Storage: Store at room temperature, away from light and moisture.
Stability: Stable under recommended conditions; check expiration date regularly.