Metoprolol (Lopressor, Toprol-XL)
A cardioselective beta blocker that slows the heart and lowers blood pressure. Available in two forms — tartrate (immediate-release, twice daily) and succinate (extended-release, once daily). Never stop abruptly.
What it's used for
Hypertension, heart failure (succinate form specifically), angina (chest pain), atrial fibrillation (rate control), prevention of repeat heart attacks, and migraine prevention (off-label). Also used for performance anxiety and essential tremor.
Typical dosing (adults)
- Metoprolol tartrate (Lopressor): 25–100 mg twice daily.
- Metoprolol succinate (Toprol-XL): 25–200 mg once daily.
- Heart failure: Start very low (12.5–25 mg succinate daily) and increase slowly over weeks.
- Take tartrate with food to improve absorption. Do not crush or split extended-release tablets.
Key interactions
- Calcium channel blockers (verapamil, diltiazem): major — combined heart rate slowing; risk of severe bradycardia or heart block.
- Clonidine: major — stopping clonidine while on a beta blocker can cause dangerous rebound hypertension.
- CYP2D6 inhibitors (fluoxetine, paroxetine, bupropion): moderate — increase metoprolol blood levels, leading to more side effects.
- Digoxin: moderate — additive heart rate slowing.
- Epinephrine (in allergic reactions): moderate — beta blockers can blunt the effect of epinephrine and worsen anaphylaxis treatment.
Common side effects
Fatigue (most common complaint), slow heart rate (bradycardia), dizziness, cold hands and feet, depression, weight gain, and sexual dysfunction. Exercise tolerance may be reduced (heart rate won't rise as much). Rare: worsening of heart failure at initiation, bronchospasm in asthmatics.
Who should be cautious
- Asthma (beta blockers can trigger bronchospasm; metoprolol is safer than non-selective beta blockers, but still use with caution).
- Diabetes (can mask low blood sugar symptoms like tremor and rapid heartbeat).
- Severe bradycardia or heart block (already slow heart rate).
- Peripheral artery disease (can worsen circulation).
- Do not stop suddenly — may cause rebound tachycardia, chest pain, or heart attack.
What to ask your pharmacist
- Am I taking the tartrate or succinate form, and does it matter?
- What heart rate is too low — when should I call my doctor?
- I'm starting an SSRI — will it interact with my metoprolol?
- How do I safely taper off metoprolol if my doctor wants to stop it?