Metoprolol: Clinical Uses and Applications
Metoprolol is primarily used for treating hypertension, angina pectoris, heart failure, and post-myocardial infarction patients to reduce mortality and morbidity. 1, 2
Primary Indications
Heart Failure
- Metoprolol significantly reduces mortality in patients with heart failure, as demonstrated in the MERIT-HF trial which showed a 34% reduction in all-cause mortality in patients with NYHA class II-IV heart failure 1
- Particularly effective in reducing sudden cardiac death and death due to progressive heart failure 3
- Should be initiated at a low dose (12.5-25 mg daily) and gradually titrated to target dose of 200 mg daily to minimize adverse effects 1
- Metoprolol CR/XL (controlled-release/extended-release) formulation is preferred for heart failure management due to once-daily dosing convenience 3
Hypertension
- Effective antihypertensive agent when used alone or in combination with thiazide-type diuretics at oral dosages of 100-450 mg daily 2
- Comparable in efficacy to other antihypertensives including propranolol, methyldopa, and thiazide diuretics 2, 4
- Effective in both supine and standing positions, making it versatile for different patient scenarios 2
Angina Pectoris
- Reduces frequency of angina attacks and increases exercise tolerance 2, 5, 6
- Effective dosage range is 100-400 mg daily, typically administered in divided doses 2
- Comparable in efficacy to propranolol in controlled clinical trials 2, 5
- Significantly increases total work performed on exercise testing compared to placebo 5, 6
Post-Myocardial Infarction
- Reduces 3-month mortality by 36% in patients with suspected or definite myocardial infarction 2
- Significantly reduces incidence of ventricular fibrillation and chest pain following initial intravenous therapy 2
- Can be administered both in the acute phase (intravenously) and as oral maintenance therapy 2
- Benefits are observed regardless of timing of administration (early ≤8 hours or later) 2
Pharmacological Properties
- Metoprolol is a relatively selective beta1-adrenergic receptor blocker 1, 3
- Primarily metabolized by CYP2D6 with elimination half-life of 3-4 hours in normal metabolizers (can be 7-9 hours in poor CYP2D6 metabolizers) 2
- Approximately 95% of the dose is recovered in urine, mostly as metabolites 2
- Beta1-selectivity may facilitate administration to certain patients (e.g., asthmatics and diabetics) in whom non-selective beta-blockers are contraindicated 7
Dosing Considerations
- For hypertension and angina: Initial doses of 100 mg daily, with range of 100-450 mg daily 2, 4
- For heart failure: Start at low dose (12.5-25 mg daily) and gradually increase at 2-week intervals to target dose of 200 mg daily 1, 3
- For post-MI: Follow the regimen used in clinical trials with careful monitoring 2
- Once or twice daily dosing may be appropriate depending on the formulation and indication 2, 4
Clinical Pearls and Caveats
- Avoid abrupt discontinuation which can lead to rebound hypertension or worsening of cardiac conditions 8
- In heart failure patients, carvedilol may be preferred over metoprolol based on the COMET trial which showed a 17% greater mortality reduction with carvedilol 1, 9
- Dose adjustment may be necessary in patients with hepatic impairment as elimination half-life can be prolonged up to 7.2 hours 2
- No significant dose adjustment needed in elderly patients or those with renal impairment 2
- Common side effects include temporary fatigue, dizziness, and headache 7