BLACK BOX WARNING
- abrupt withdrawal may precipitate angina or MI
metoprolol succinate
Brand: Toprol-XL
⚠ BBW Prototype Drug
Drug Class: beta-blocker
Drug Family: antihypertensive
Subclass: selective beta-1 blocker (extended-release)
Organ Systems: cardiovascular
Mechanism of Action
Cardioselective beta-1 receptor antagonist reducing heart rate, myocardial contractility, and renin release; extended-release formulation provides 24-hour coverage.
beta-1 adrenergic receptor
Indications
- hypertension
- chronic heart failure (HFrEF)
- angina
- post-MI
- migraine prophylaxis
Contraindications
- decompensated heart failure
- cardiogenic shock
- severe bradycardia
- heart block (>1st degree) without pacemaker
- sick sinus syndrome
Adverse Effects
Common
- bradycardia
- fatigue
- dizziness
- cold extremities
Serious
- bronchospasm (high doses)
- masking hypoglycemia
- heart block
- abrupt withdrawal (rebound hypertension/angina)
Pharmacokinetics (ADME)
| Absorption | 50% oral bioavailability (extensive first-pass) |
| Distribution | moderate lipophilicity; crosses BBB |
| Metabolism | extensive hepatic CYP2D6 |
| Excretion | renal (primarily as metabolites) |
| Half-life | 3-7 hours (IR), effective 24h (XL) |
| Onset | 1-2 hours |
| Peak | 6-12 hours (XL) |
| Duration | 24 hours |
| Protein Binding | 12% |
| Vd | 3.2-5.6 L/kg |
Drug Interactions
| Drug / Agent | Mechanism | Severity |
|---|---|---|
| verapamil or diltiazem | additive AV block and bradycardia | major |
| clonidine | rebound hypertension on clonidine withdrawal enhanced | major |
| CYP2D6 inhibitors (fluoxetine) | increased metoprolol levels | moderate |
Nursing Considerations
- Count apical pulse for 1 minute before administration; hold if <50 bpm
- Never abruptly discontinue — taper over 1-2 weeks
- Succinate (XL) preferred over tartrate in HFrEF (MERIT-HF trial)
- Monitor for signs of bronchospasm in asthma/COPD patients
Clinical Pearls
- MERIT-HF: reduced all-cause mortality in HFrEF
- Cardioselective at low doses but selectivity lost at high doses — caution in reactive airway disease
- XL formulation specifically studied in HF; IR (tartrate) is NOT preferred for HF
Safety Profile
Pregnancy use-with-caution
Lactation use-with-caution
Renal Adjustment Not required
Hepatic Adjustment Required
TDM Not required
Concordance Terms
Cross-referenced clinical concepts — click any term to see all content where it appears.