Metoprolol
Brand names: Lopressor (tartrate), Toprol-XL (succinate)
Class: ❤️ Beta-Blockers
What examiners watch for is whether you can distinguish metoprolol succinate (Toprol-XL) from tartrate (Lopressor) on a heart-failure question. Both are cardioselective beta-1 antagonists used for hypertension, angina, post-MI mortality reduction, and atrial fibrillation rate control. Only the succinate (long-acting) salt has HFrEF mortality benefit — alongside carvedilol and bisoprolol — because steady-state beta-1 blockade is what reverses remodeling. Cardioselectivity makes metoprolol relatively safer than propranolol in COPD or asthma, but no beta-blocker is risk-free at high dose. Hold for symptomatic bradycardia or hypotension. Counsel diabetics on insulin: metoprolol can mask the adrenergic warning signs of hypoglycemia. Never start in decompensated HF — wait until euvolemic.
✅ Indications
HTN, angina, post-MI, CHF (succinate only), rate control in a-fib.
⚙️ Mechanism of Action
Cardioselective β₁-blocker.
📏 Dosing
Tartrate: 25–100 mg BID. Succinate (XL): 25–200 mg daily.
🚫 Contraindications
Severe bradycardia, 2nd/3rd degree AV block, decompensated CHF (start when stable).
⚠️ Adverse Effects
Bradycardia, fatigue, hypotension, cold extremities, masked hypoglycemia.
🔬 Monitoring
HR, BP; titrate in CHF per mortality protocols.
💎 Board Pearls
- ⚡ TARTRATE = immediate-release (BID dosing, rate control). SUCCINATE = extended release (once daily, proven CHF mortality benefit).
- 🫀 CHF: metoprolol SUCCINATE, carvedilol, or bisoprolol — the big three.
Practice Questions
A 58-year-old woman with type 1 diabetes on basal-bolus insulin recently started metoprolol tartrate (Lopressor) 50 mg BID after a non-ST-elevation MI. She calls the nurse advice line worried because she "can't tell when her sugar is dropping anymore." Her husband has had to bring her juice twice in the past week after finding her confused. When counseling her by phone, the NP explains that metoprolol can blunt most of the classic adrenergic warning signs of hypoglycemia. Which of the following symptoms is LEAST likely to be masked by her beta-blocker?
Related Drugs in This Class
- Carvedilol — Coreg
- Propranolol — Inderal
- Labetalol — Trandate, Normodyne
Sources
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