Metoprolol
Generic Name
Brand Names
Pronunciation
LASA Warnings
Pharmacologic Class
DEA Schedule
Pregnancy & Lactation
Pregnancy category C; excreted in breast milk
Black Box Warning
Abrupt discontinuation may exacerbate angina / cause MI
Mechanism of Action
Competitively blocks β₁‑adrenergic receptors in the heart, decreasing cAMP and calcium entry → negative chronotropy, inotropy, and dromotropy. Reduces myocardial oxygen demand.
Receptor Binding
High affinity for β₁ (cardioselective); at higher doses loses selectivity.
Cellular Transport
Absorbed via small intestine; P‑glycoprotein substrate.
Barrier Penetration
| Blood-Brain Barrier (BBB) | Moderate (lipophilic, may cause CNS side effects) |
| Bone / Synovial Fluid | Low |
| Placental Transfer | Yes |
Pharmacokinetics
| Absorption & Bioavailability | Rapid, bioavailability ~50% (first‑pass metabolism). |
| Hepatic Metabolism / CYP450 Profile | <p><strong>Metabolism:</strong> Hepatic CYP2D6.</p> |
| Active & Toxic Metabolites | None |
| Excretion Pathway & Half-Life | Renal; half‑life 3‑7 hours. |
Pharmacogenomics
CYP2D6 poor metabolisers have 5‑fold higher plasma concentrations → risk of excessive bradycardia. Consider dose reduction or alternative (Atenolol).
Indications & Dosing
| Indication Name | Approval Status | Adult Dosing | Pediatric/Neonatal Dosing |
|---|---|---|---|
| Hypertension | fda | <p>Metoprolol tartrate 25‑100 mg PO BID; succinate 25‑200 mg PO daily</p> | <p>Not established for HTN</p> |
Weight‑Based Rules
Not weight‑based.
Max Lifetime Dose
Organ Impairment Dosing
| Renal Adjustments (CrCl) | <p>No adjustment</p> |
| Hepatic Adjustments (Child-Pugh) | <p>Reduce dose in severe impairment</p> |
| Dialysis, CRRT & ECMO Dosing | <p>Not significantly removed</p> |
Special Populations
| Geriatric (Beers Criteria) | <ul> <li> <p class="ds-markdown-paragraph"><span class="">Start low, titrate slowly (Beers Criteria: avoid as first‑line in older adults due to risk of bradycardia)</span></p> </li> </ul> |
| Bariatric Surgery Adjustments | <p>No adjustment</p> |
Preparation & Stability
Store at room temperature. IV formulation: 1 mg/mL.
Compatible Diluents
IV Administration Rules
| IV Push Rate / Bolus Limits | 1 mg/min |
| Y-Site Incompatibilities | <p>Furosemide, Heparin</p> |
Enteral & PO Rules
Take with food. Do not crush extended‑release.
REMS Program
None.
Adverse Effects
| System | Side Effect | Frequency |
|---|---|---|
| Cardiovascular | Bradycardia, Hypotension | Common (>10%) |
| Neurologic | Fatigue, Dizziness | Occasional (1-10%) |
| Other | Bronchospasm (rare) | Rare (<1%) |
Contraindications
Severe bradycardia, sick sinus syndrome without pacemaker, cardiogenic shock, decompensated heart failure.
Drug Interactions
- Calcium channel blockers (verapamil): additive negative inotropic effect → bradycardia, heart block
- Clonidine: rebound hypertension if stopped abruptly
Toxicology / Overdose
Overdose: severe bradycardia, hypotension, bronchospasm. Management: Glucagon 5‑10 mg IV (positive inotrope independent of β‑receptors), atropine, pacing.
Dialyzable?
Monitoring Parameters
Heart rate, blood pressure, ECG (PR interval).
Mnemonics
BETA‑1: Beta‑Ends The Action (Bronchospasm is β₂, not β₁).
Buzzwords
Board Focus
Metoprolol is preferred over propranolol in patients with COPD due to β₁ selectivity. Abrupt withdrawal can cause rebound tachycardia and MI.
Trivia
Relative Cost
Availability
Patient Education
Take this medicine exactly as prescribed. Do not stop suddenly – it can worsen your heart condition. If you feel dizzy, rise slowly from sitting or lying down.
Specialty Template
Tapering Protocols
Gradually reduce dose over 1‑2 weeks to avoid rebound hypertension, angina, or MI.
Missed Dose
If you miss a dose, take it as soon as you remember unless it is within 4 hours of the next dose. Do not double dose.