Lopressor 100 mg Tablets

Brand Name

This medication is marketed under the trade name Lopressor, a label widely recognized among healthcare professionals for its cardiovascular applications.

International Nonproprietary Name (INN)

The active ingredient is identified globally as metoprolol, ensuring its consistent recognition across medical systems worldwide.

Form of Release

The drug is available in multiple forms, including immediate-release tablets, extended-release tablets, and an injectable solution for intravenous use. These formulations come in various strengths, offering flexibility for oral or parenteral administration based on patient requirements while maintaining stability under standard storage conditions.

Composition

Metoprolol tartrate serves as the primary active substance in immediate-release tablets and injectable forms, while metoprolol succinate is used in extended-release tablets, both designed to influence specific physiological pathways. Inactive ingredients in tablets include microcrystalline cellulose, lactose monohydrate, sodium starch glycolate, and magnesium stearate, which provide structural support and facilitate dissolution or controlled release. The injectable solution contains sodium chloride and citric acid to ensure compatibility with bodily fluids. Some oral formulations may feature a coating of hypromellose or colorants for identification. Each component is carefully integrated to enhance the therapeutic action of metoprolol without altering its potency.

Pharmacologic Properties

Pharmacodynamics

This medication acts as a selective beta-1 adrenergic receptor blocker, primarily targeting receptors in the heart to exert its effects. By inhibiting the action of catecholamines like adrenaline, it reduces heart rate, myocardial contractility, and cardiac output, thereby decreasing oxygen demand and blood pressure. Its selectivity for beta-1 receptors minimizes effects on beta-2 receptors in the lungs and peripheral vasculature, reducing bronchial constriction risks compared to non-selective agents. It also suppresses renin release from the kidneys, contributing to its antihypertensive action. Effects begin within 15 to 30 minutes of oral administration or minutes of intravenous use, with peak activity at one to four hours, offering sustained benefits with regular dosing. This targeted mechanism supports its utility in cardiovascular regulation.

Pharmacokinetics

Following oral administration, the drug absorbs rapidly from the gastrointestinal tract, with bioavailability averaging 50% for immediate-release forms due to first-pass hepatic metabolism, and slightly higher for extended-release due to slower release. Food enhances absorption slightly. Peak plasma concentrations occur within one to two hours for immediate-release tablets and four to six hours for extended-release, while intravenous delivery achieves instant levels. Metoprolol binds about 12% to plasma proteins and distributes widely, crossing the blood-brain barrier and reaching cardiac tissue efficiently. It undergoes extensive hepatic metabolism via cytochrome P450 2D6, producing inactive metabolites. Elimination occurs primarily through urine, with less than 5% excreted unchanged, and a half-life of three to seven hours, extended in hepatic impairment or poor metabolizers.

Indications for Use

This medication is prescribed for a range of conditions requiring cardiovascular control. It is a key treatment for hypertension, lowering blood pressure by reducing cardiac output and renin activity. It manages angina pectoris by decreasing myocardial oxygen demand, improving exercise capacity in affected patients. In acute myocardial infarction, it reduces infarct size and mortality risk by limiting cardiac stress, often initiated intravenously then transitioned to oral forms. It treats supraventricular tachycardia and other arrhythmias by slowing atrioventricular node conduction. Beyond cardiology, it may control symptoms in hyperthyroidism, such as palpitations, and reduce migraine frequency by stabilizing vascular responses. Its versatility makes it a cornerstone in both acute and chronic management of these disorders.

Contraindications

Certain conditions preclude the use of this drug to safeguard patient health. Hypersensitivity to metoprolol or beta-blocker components prohibits its administration, as reactions could range from skin irritation to anaphylaxis. Severe bradycardia, second- or third-degree heart block, or sick sinus syndrome without a pacemaker contraindicates it due to its heart rate-lowering effects. It is avoided in cardiogenic shock or decompensated heart failure requiring inotropic support, where beta-blockade could worsen cardiac function. Significant hypotension or severe peripheral artery disease limits its use to prevent circulatory compromise. Asthma or severe chronic obstructive pulmonary disease with reactive airway components requires caution, though its selectivity reduces risks compared to non-selective agents. Uncontrolled diabetes may mask hypoglycemia signs, necessitating careful consideration.

Method of Administration and Dosage

How to Take

Tablets are taken orally, with immediate-release forms typically with or after meals to reduce gastrointestinal upset, and extended-release forms at any consistent time daily. Swallowing them whole with water ensures proper delivery, avoiding crushing extended-release tablets to maintain their release profile. The injectable solution is administered intravenously by healthcare professionals, often in acute settings. Consistent timing supports stable blood levels for optimal control.

Dosage for Adults and Children

For adults with hypertension, immediate-release dosing starts at 50 mg twice daily, adjustable to 100 mg to 400 mg daily in divided doses, while extended-release begins at 25 mg to 100 mg once daily, up to 400 mg. In angina, 100 mg to 400 mg daily is common, tailored to symptom relief. Acute myocardial infarction may involve 5 mg intravenous doses every two minutes up to 15 mg, followed by 50 mg orally every six hours, transitioning to 100 mg twice daily. Arrhythmias often require 25 mg to 100 mg two to three times daily. Children with hypertension or arrhythmias receive 1 mg to 2 mg per kilogram daily, divided into two doses, with a maximum of 6 mg per kilogram, adjusted under specialist care. Monitoring ensures efficacy and safety.

Dose Adjustment in Specific Conditions

Renal impairment generally requires no adjustment, as excretion is hepatic, though monitoring for fluid status is wise. Hepatic dysfunction necessitates lower doses, starting at 25 mg daily, due to slowed metabolism and risk of accumulation, particularly in poor metabolizers. Elderly patients or those with reduced cardiac reserve may begin with 25 mg daily to minimize bradycardia or hypotension. Gradual titration and regular assessments tailor dosing to individual needs, especially in compromised states.

Side Effects

This medication may elicit various unintended reactions, though most are transient. Fatigue, dizziness, or drowsiness are frequent, often tied to reduced cardiac output or central effects, particularly early in therapy. Bradycardia or cold extremities might occur due to slowed heart rate and peripheral vasoconstriction. Gastrointestinal issues like nausea, diarrhea, or stomach discomfort affect some users but usually subside with time. Shortness of breath or wheezing can emerge in those with airway sensitivity, though less common due to its selectivity. Rarely, severe effects like depression, vivid dreams, or significant hypotension occur, requiring prompt medical attention. Patient feedback and periodic evaluations help manage these responses effectively.

Overdose

Symptoms of Overdose

Excessive intake can lead to severe bradycardia, causing weakness, fainting, or cardiac arrest from excessive beta-blockade. Hypotension may result in dizziness, confusion, or shock due to reduced cardiac output and vascular tone. Respiratory difficulty or bronchospasm might develop in susceptible individuals, complicating breathing. Seizures or coma could occur in extreme cases, reflecting central nervous system depression. Symptoms typically appear within hours and escalate without intervention, highlighting the drug’s potent cardiovascular impact.

First Aid Measures

In an overdose situation, discontinue administration immediately and seek urgent medical assistance. If ingestion is recent, gastric lavage or activated charcoal may reduce absorption, performed under professional supervision. Intravenous atropine addresses bradycardia, while fluids or vasopressors like dopamine support blood pressure. Bronchodilators like albuterol relieve airway constriction, and glucagon may counter beta-blockade effects on the heart. Continuous cardiac monitoring stabilizes the patient until recovery, focusing on restoring normal rhythm and circulation.

Drug Interactions

Effects on Other Medications

This drug influences the performance of various medications when used together. It can amplify the effects of other antihypertensives, risking excessive blood pressure reduction, so careful dose calibration is needed. Concurrent use with calcium channel blockers like verapamil heightens bradycardia or heart block risks, requiring close oversight. It may reduce the efficacy of bronchodilators like salbutamol by opposing beta-2 stimulation in rare cases. Antidiabetic agents’ hypoglycemic effects might be masked, necessitating glucose monitoring. Adjustments minimize these interactions effectively.

Compatibility with Alcohol and Food

Alcohol consumption may intensify drowsiness or hypotension, particularly due to additive central depression, so moderation is advised. Food enhances absorption of immediate-release forms, improving bioavailability, while extended-release forms are less affected, allowing flexible timing. No strict dietary restrictions apply beyond avoiding excessive stimulants that could counteract its calming effects.

Special Precautions

Use During Pregnancy and Breastfeeding

Lopressor is not recommended during pregnancy unless benefits outweigh risks, as it may cause fetal bradycardia or growth restriction, based on limited human data. It passes into breast milk, potentially affecting infant heart rate, so nursing mothers should consult their physician, possibly opting for alternatives to reduce exposure.

Impact on Driving and Machinery Operation

Dizziness or fatigue, especially at initiation or dose changes, may impair driving or machinery operation. Patients should assess their tolerance before engaging in such activities, ensuring safety for themselves and others.

Considerations for Elderly and Pediatric Populations

Elderly individuals may require lower starting doses due to heightened sensitivity to bradycardia or hypotension, with regular tolerance checks. In children, its use is tailored to specific conditions like arrhythmias, with weight-based dosing adjusted cautiously under specialist guidance to avoid developmental impact. Personalized care optimizes safety across these groups.