Lopressor

Lopressor (metoprolol tartrate) is a cardioselective beta-1 adrenergic receptor blocking agent, representing a cornerstone in modern cardiovascular pharmacotherapy. It is specifically formulated to manage hypertension, angina pectoris, and hemodynamic stability following myocardial infarction. By selectively antagonizing beta-1 receptors predominantly located in cardiac tissue, Lopressor reduces heart rate, myocardial contractility, and conduction velocity, thereby decreasing myocardial oxygen demand. Its well-established pharmacokinetic profile and extensive clinical evidence base make it a first-line option for long-term cardiovascular risk modification under appropriate medical supervision.

Features

• Active Ingredient: Metoprolol tartrate
• Pharmacologic Class: Cardioselective beta-1 adrenergic receptor antagonist
• Available Formulations: Immediate-release tablets (25 mg, 50 mg, 100 mg); injectable solution for intravenous administration (1 mg/mL)
• Bioavailability: Approximately 50% following oral administration due to significant first-pass metabolism
• Protein Binding: 10–12%
• Metabolism: Hepatic, primarily via CYP2D6 isoenzyme (exhibiting genetic polymorphism)
• Elimination Half-life: 3–7 hours; prolonged in poor metabolizers and patients with hepatic impairment
• Excretion: Renal (≤10% as unchanged drug)

Benefits

• Reduces Systolic and Diastolic Blood Pressure: Lowers arterial pressure through decreased cardiac output and reduced renin secretion from juxtaglomerular apparatus.
• Decreases Myocardial Oxygen Demand: Mitigates anginal symptoms and improves exercise tolerance in chronic stable angina by lowering heart rate and contractility.
• Improves Post-Infarct Survival: Demonstrated mortality benefit when initiated early in acute myocardial infarction through anti-arrhythmic and anti-ischemic effects.
• Provides Rate Control: Effective in managing ventricular rate in atrial fibrillation and flutter.
• Cardioprotective Effects: May attenuate pathological remodeling in chronic heart failure when used as part of guideline-directed medical therapy.
• Favorable Selectivity Profile: Lower incidence of bronchospasm and peripheral vasoconstriction compared to non-selective beta-blockers at therapeutic doses.

Common use

Lopressor is indicated for the management of hypertension, either as monotherapy or in combination with other antihypertensive agents. It is employed in the long-term treatment of chronic stable angina pectoris to reduce frequency and severity of ischemic episodes. In the setting of acute myocardial infarction, it is used both intravenously and orally to improve survival and reduce reinfarction risk. Off-label uses include symptomatic control in supraventricular tachyarrhythmias, migraine prophylaxis, essential tremor, and adjunctive therapy in hyperthyroidism to control sympathetic symptoms.

Dosage and direction

Hypertension: Initial dose 50 mg twice daily or 100 mg once daily; may be increased at weekly intervals to maximum 450 mg daily in divided doses.
Angina Pectoris: 50 mg twice daily; titrate to 100–200 mg twice daily based on response.
Myocardial Infarction: Early treatment involves IV administration (5 mg every 2 minutes for 3 doses) followed by oral therapy 50 mg every 6 hours for 48 hours, then maintenance 100 mg twice daily.
Administration: Should be taken with or immediately following meals to enhance bioavailability. Tablets should be swallowed whole; not to be crushed or chewed. Dosage adjustments required in hepatic impairment and CYP2D6 poor metabolizers.

Precautions

Abrupt discontinuation may precipitate angina exacerbation, myocardial infarction, or ventricular arrhythmias; taper over 1–2 weeks. Use caution in patients with compensated heart failure; may precipitate acute decompensation if initiated at high doses. May mask hypoglycemic symptoms in diabetics and signs of hyperthyroidism. Can cause fatigue, dizziness, or hypotension; advise against operating machinery until response is known. Periodic monitoring of heart rate, blood pressure, and ECG recommended. Not recommended during pregnancy unless potential benefit justifies potential fetal risk.

Contraindications

• Severe bradycardia (heart rate <45–50 bpm)
• Second- or third-degree heart block without functioning pacemaker
• Cardiogenic shock
• Decompensated heart failure requiring inotropic support
• Sick sinus syndrome
• Hypersensitivity to metoprolol or any component of formulation
• Severe peripheral arterial circulatory disorders

Possible side effect

Common (≥1%): Fatigue, dizziness, depression, bradycardia, diarrhea, pruritus, rash
Less common: Insomnia, nightmares, bronchospasm (in susceptible patients), cold extremities, Raynaud’s phenomenon
Serious (require medical attention): Symptomatic bradycardia, heart failure exacerbation, severe hypotension, AV block, bronchospasm, hallucinations, hepatotoxicity, thrombocytopenia
Rare: Peyronie’s disease, retroperitoneal fibrosis

Drug interaction

Potentiates hypotension/bradycardia: Concomitant use with other beta-blockers, calcium channel blockers (especially verapamil/diltiazem), digoxin
Reduces efficacy: NSAIDs may attenuate antihypertensive effect
Metabolic interactions: CYP2D6 inhibitors (quinidine, fluoxetine, paroxetine) increase metoprolol concentrations
Hypoglycemic agents: May mask tachycardia associated with hypoglycemia; dose adjustment may be needed
Vasodilators: Enhanced hypotensive effect with nitrates, hydralazine
Anesthetics: Increased myocardial depression with general anesthetics

Missed dose

If a dose is missed, take as soon as remembered unless close to next scheduled dose. Do not double dose to make up for missed administration. Maintain regular dosing schedule; inconsistent dosing may lead to breakthrough hypertension or angina.

Overdose

Manifests as severe bradycardia, hypotension, heart failure, bronchospasm, hypoglycemia, and coma. Treatment includes gastric lavage if recent ingestion, activated charcoal, and supportive measures. Atropine 0.5–1 mg IV for bradycardia; glucagon 2–10 mg IV followed by infusion may reverse cardiac effects. Cardiac pacing, vasopressors (norepinephrine preferred over epinephrine), and bronchodilators may be required. Hemodialysis is not effective due to extensive protein binding.

Storage

Store at controlled room temperature (20–25°C/68–77°F). Protect from moisture and light. Keep in original container with tight closure. Do not use beyond expiration date. Keep out of reach of children. Do not transfer to alternative containers as stability may be compromised.

Disclaimer

This information is for educational purposes and does not constitute medical advice. Lopressor is a prescription medication requiring individualized dosing and supervision by a qualified healthcare professional. Not all uses, precautions, or interactions are listed. Patients should consult their physician for diagnosis, treatment decisions, and monitoring. Never adjust dosage or discontinue medication without medical guidance.

Reviews

“Lopressor has been instrumental in maintaining my patients’ blood pressure within target ranges with predictable pharmacokinetics. The cardioselectivity offers a favorable side effect profile compared to non-selective agents.” — Cardiologist, 15 years experience
“Effective for rate control in atrial fibrillation, though requires careful titration in elderly patients. The immediate-release formulation allows for flexible dosing in hospitalized patients.” — Clinical Pharmacist, academic medical center
“While generally well-tolerated, some patients report fatigue and exercise intolerance. The twice-daily dosing can affect adherence compared to once-daily alternatives.” — Internal Medicine Physician
“Standard therapy in our post-MI protocol. The mortality benefit evidence is robust, and we’ve observed excellent hemodynamic control when initiated appropriately.” — Critical Care Specialist