What medication can be given to a patient with tachycardia to lower their heart rate?

Medications to Lower Heart Rate in Tachycardia

Beta-blockers are the first-line agents for acute heart rate control in most tachycardias, with intravenous metoprolol (5 mg IV bolus over 2 minutes, repeated every 5 minutes up to 15 mg total) being the most commonly used agent for rapid rate reduction. 1

First-Line Agents: Beta-Blockers

Intravenous Beta-Blockers for Acute Rate Control

Metoprolol is the most frequently used IV beta-blocker for acute tachycardia:

• Dosing: 2.5-5 mg IV bolus over 1-2 minutes, repeat every 5 minutes as needed based on hemodynamic response, maximum total dose 15 mg 1
• Indications: Stable narrow-complex tachycardias unresponsive to adenosine or vagal maneuvers, atrial fibrillation/flutter rate control, certain polymorphic VT associated with acute ischemia 1
• Onset: 1-2 minutes 1
• Duration: 5-8 hours 1

Esmolol offers ultra-short duration for high-risk patients:

• Dosing: 500 mcg/kg (0.5 mg/kg) IV bolus over 1 minute, followed by infusion of 50-300 mcg/kg/min 1
• Advantage: Half-life of 10-30 minutes allows rapid titration and reversal if hypotension occurs 1
• Onset: 1-2 minutes 1

Propranolol (non-selective beta-blocker):

• Dosing: 0.5-1 mg IV over 1 minute, repeated up to total dose of 0.1 mg/kg 1, 2
• Indications: Supraventricular arrhythmias including Wolff-Parkinson-White syndrome, thyrotoxicosis, digitalis-induced arrhythmias, catecholamine-induced arrhythmias during anesthesia 2
• Onset: Within 5 minutes 2

Oral Beta-Blockers for Ongoing Rate Control

Metoprolol tartrate: 25-100 mg twice daily 1

Metoprolol succinate (extended-release): 50-400 mg once daily 1, 3

Atenolol: 25-100 mg once daily 1

Carvedilol: 3.125-25 mg twice daily 1

Second-Line Agents: Calcium Channel Blockers

Nondihydropyridine Calcium Channel Antagonists

Diltiazem is highly effective for rate control:

• IV dosing: 0.25 mg/kg IV bolus over 2 minutes, then 5-15 mg/h infusion 1
• Oral dosing: 120-360 mg once daily (extended-release) 1
• Advantages: Improves quality of life and exercise tolerance, preferred over beta-blockers in patients with bronchospasm or COPD 1

Verapamil:

• IV dosing: 0.075-0.15 mg/kg IV bolus over 2 minutes, may give additional 10 mg after 30 minutes, then 0.005 mg/kg/min infusion 1
• Oral dosing: 180-480 mg once daily (extended-release) 1
• Special indication: Can terminate multifocal atrial tachycardia in some patients 1

Third-Line Agents

Digoxin

• IV dosing: 0.25 mg IV with repeat dosing to maximum 1.5 mg over 24 hours 1
• Oral maintenance: 0.125-0.25 mg daily 1
• Major limitation: Slow onset (60 minutes to effect, peak at 6 hours), ineffective in high sympathetic states, no longer first-line therapy 1
• Best use: Combination with beta-blockers for additive rate control in atrial fibrillation 1

Amiodarone

• IV dosing: 150 mg over 10 minutes, repeated if necessary, then 1 mg/min for 6 hours, then 0.5 mg/min (maximum 2.2 g/24 hours) 1
• Oral dosing: 100-200 mg daily 1
• Indications: Stable irregular narrow-complex tachycardia (atrial fibrillation), pre-excited atrial arrhythmias, when other measures unsuccessful or contraindicated 1

Critical Contraindications to Beta-Blockers and Calcium Channel Blockers

Absolute contraindications to IV beta-blockers:

• Signs of heart failure, low output state, or decompensated heart failure 1, 3
• Second or third-degree heart block without functioning pacemaker 1
• Active asthma or severe reactive airway disease 1, 3
• Systolic BP <100-120 mmHg with symptoms 1, 3
• Heart rate <60 bpm or >110 bpm (in acute MI setting) 1, 3
• PR interval >0.24 seconds 3

Avoid in pre-excited atrial fibrillation: Digoxin, nondihydropyridine calcium channel blockers, and IV amiodarone should NOT be used as they may accelerate ventricular response and cause ventricular fibrillation 1

Algorithm for Selecting Rate-Control Agent

Step 1: Assess Hemodynamic Stability

• Unstable (hypotension, pulmonary edema, ongoing ischemia): Electrical cardioversion, NOT pharmacologic rate control 1
• Stable: Proceed to pharmacologic therapy 1

Step 2: Check for Contraindications

• Heart failure with reduced ejection fraction: Use beta-blockers cautiously (start low, go slow) or consider digoxin + beta-blocker combination 1
• Asthma/COPD: Prefer diltiazem or verapamil over beta-blockers 1
• Pre-excitation (WPW): Avoid AV nodal blockers; use procainamide or amiodarone 1

Step 3: Choose Initial Agent

• First choice: IV metoprolol 5 mg over 2 minutes, repeat every 5 minutes up to 15 mg total 1
• If beta-blocker contraindicated: IV diltiazem 0.25 mg/kg over 2 minutes 1
• If both contraindicated or failed: IV amiodarone 150 mg over 10 minutes 1

Step 4: Monitor Response

• Target heart rate <110 bpm (lenient control) or <80 bpm (strict control) for atrial fibrillation 3
• Target heart rate 50-60 bpm for other indications unless limiting side effects occur 3

Special Populations

Multifocal atrial tachycardia: IV metoprolol (mean dose 6.5 mg) or oral metoprolol (mean dose 32.5 mg) highly effective, with 68% conversion to sinus rhythm 4, 5, 6

Pregnant patients: Metoprolol is considered safe first-line agent, though use lowest effective dose due to association with intrauterine growth retardation 3

Elderly patients (>70 years): Start with lower doses and titrate cautiously, particularly in acute MI setting where cardiogenic shock risk is elevated 1, 3

Common Pitfalls to Avoid

• Never give full 15 mg metoprolol as single rapid bolus: Significantly increases hypotension and bradycardia risk 3
• Don't use IV beta-blockers in decompensated heart failure: Wait for clinical stabilization 1, 3
• Don't use AV nodal blockers in pre-excited atrial fibrillation: May cause ventricular fibrillation 1
• Don't rely on digoxin alone for acute rate control: Onset too slow (60+ minutes) and ineffective in high sympathetic states 1
• Don't abruptly discontinue beta-blockers: Associated with 2.7-fold increased mortality risk, severe angina exacerbation, MI, and ventricular arrhythmias 3