What IV medication is recommended for a patient with a normal EKG, tachycardia, and BP 115/71 mmHg?

IV Adenosine is the First-Line Medication for This Patient

For a hemodynamically stable patient with a heart rate of 170 bpm and normal blood pressure (115/71 mmHg), IV adenosine is the recommended first-line medication, administered as a 6 mg rapid IV bolus followed by immediate saline flush, with a repeat 12 mg dose if needed. 1, 2, 3

Clinical Reasoning

Patient Stability Assessment

• With a BP of 115/71 mmHg, this patient is hemodynamically stable despite the tachycardia 2
• Heart rate of 170 bpm with a "normal EKG" (presumably narrow-complex) suggests supraventricular tachycardia (SVT) 1, 2
• Stable patients do not require immediate cardioversion and should receive pharmacologic therapy first 1, 2

Why Adenosine is First-Line

Adenosine is specifically recommended as first-line treatment for narrow-complex tachycardia in stable patients because it:

• Terminates almost all episodes of PSVT involving the AV node within 30 seconds 4
• Has an exceptionally short half-life (<10 seconds), allowing rapid repeat dosing if ineffective 4
• Serves dual purpose: therapeutic (terminates rhythm) and diagnostic (unmasks underlying rhythm during transient AV block) 1, 2, 5
• Converts 88-93% of true PSVT cases to sinus rhythm 6

Exact Dosing Protocol

Initial dose: 6 mg rapid IV bolus injected as proximal to the heart as possible, followed immediately by rapid saline flush 3

If no response within 1-2 minutes: 12 mg rapid IV bolus with saline flush 3

If still no response: Repeat 12 mg dose once more (some sources support up to 18 mg total) 3

Alternative Medications if Adenosine Fails

If adenosine is ineffective or contraindicated, the following are second-line options for stable narrow-complex tachycardia:

IV calcium channel blockers:

• Diltiazem: 0.25 mg/kg IV bolus over 2 minutes 3
• Verapamil: 5-10 mg (0.075-0.15 mg/kg) IV bolus over 2 minutes 3, 7

IV beta-blockers: 3, 2

• Metoprolol: 2.5-5 mg IV bolus over 2 minutes, can repeat every 10 minutes up to 3 doses 3
• Esmolol: 500 mcg/kg IV bolus over 1 minute, followed by infusion 3

Critical Safety Considerations

Adenosine must be given with immediate access to:

• Defibrillator (adenosine can rarely induce ventricular fibrillation, even without accessory pathways) 8
• Transcutaneous pacing equipment 8, 4
• Resuscitation equipment 8

Common transient side effects (<1 minute duration):

• Flushing, dyspnea, chest pain 3, 4
• Transient AV block (therapeutic effect) 3
• Brief asystole or bradycardia 4

Contraindications to adenosine:

• Known pre-excitation syndromes with atrial fibrillation (can cause ventricular fibrillation) 1, 8
• Second or third-degree AV block without pacemaker 3
• Sick sinus syndrome without pacemaker 3
• Severe bronchospasm 3

What NOT to Give

Avoid verapamil or diltiazem if:

• Wide-complex tachycardia of uncertain etiology (could be ventricular tachycardia) 2
• Pre-excitation syndromes with atrial fibrillation 1
• Decompensated heart failure 3
• Hypotension 3

Amiodarone is NOT first-line for stable narrow-complex tachycardia—it is reserved for wide-complex tachycardia or refractory cases 1, 2

If Patient Becomes Unstable

Immediate synchronized cardioversion is indicated if the patient develops:

• Hypotension with signs of shock 1, 2
• Altered mental status 2
• Chest pain suggesting ischemia 2
• Acute heart failure 2