Is deriphyllin (a methylxanthine) safe to administer in patients with tachycardia?

Deriphyllin Should NOT Be Administered in Patients with Tachycardia

Deriphyllin (theophylline) is contraindicated in patients with tachycardia because methylxanthines directly cause and exacerbate cardiac arrhythmias, including supraventricular and ventricular tachycardias, particularly at therapeutic and supratherapeutic concentrations. 1

Mechanism of Harm

Theophylline produces direct proarrhythmic effects through multiple mechanisms:

• Multifocal atrial tachycardia and atrial flutter occur at serum concentrations ≥15 mcg/mL in patients with hypoxia secondary to COPD 1
• Supraventricular tachycardia is associated with short-term theophylline use (relative risk 4.0) 2
• Sinus tachycardia occurs in 100% of acute overdose cases and 86-100% of chronic overdose cases 1
• Ventricular arrhythmias with hemodynamic instability occur in 7-14% of theophylline toxicity cases 1

Evidence from FDA Drug Label

The FDA label for theophylline explicitly documents cardiac arrhythmias as adverse reactions:

• Cardiac arrhythmias occur when peak serum concentrations exceed 20 mcg/mL 1
• Other supraventricular tachycardias occur in 22% of acute overdose and 11-21% of chronic overdose cases 1
• Atrial fibrillation or flutter occurs in 1-12% of cases 1
• Ventricular premature beats occur in 3-21% of cases 1

Clinical Context: Tachycardia Management Guidelines

Current guidelines for tachycardia management explicitly avoid agents that worsen arrhythmias:

• Adenosine is the drug of choice for acute SVT termination after vagal maneuvers 3, 4
• Beta-blockers are reasonable for acute treatment of junctional tachycardia 3
• Calcium channel blockers (diltiazem, verapamil) are second-line agents for SVT 4, 5
• Theophylline reduces adenosine's effectiveness by antagonizing its effects 3

Comparative Safety Data

Research evidence confirms theophylline's arrhythmogenic potential:

• A nested case-control study of 710 cases found short-term theophylline use associated with arrhythmias (RR 1.8,95% CI 1.0-3.3) 2
• Theophylline was specifically associated with atrial fibrillation risk, especially with new courses of therapy 2
• In contrast, doxofylline (an alternative methylxanthine) significantly reduced ventricular premature beats compared to aminophylline (p<0.05) 6

Critical Clinical Pitfalls

Common mistake: Administering theophylline for bronchospasm in patients with concurrent tachycardia, assuming the respiratory benefit outweighs cardiac risk. This is incorrect—the arrhythmogenic effects can be life-threatening 1

Drug interaction concern: Theophylline antagonizes adenosine, the first-line agent for SVT termination, making subsequent arrhythmia management more difficult 3

Monitoring inadequacy: Even therapeutic concentrations (10-20 mcg/mL) can cause persistent tachycardia in susceptible patients 1

Alternative Bronchodilator Options

For patients requiring bronchodilation who have tachycardia:

• Beta-2 agonists (though these also carry arrhythmia risk, particularly ventricular arrhythmias, RR 7.1) 2
• Antimuscarinics (ipratropium) have lower cardiac risk profile 2
• Doxofylline may be safer than aminophylline if a methylxanthine is absolutely necessary 6

Absolute Contraindications

Deriphyllin must be avoided in:

• Any patient presenting with active tachycardia (supraventricular or ventricular) 1
• Patients with history of cardiac arrhythmias 1, 2
• Patients with hypoxia and COPD (highest risk for multifocal atrial tachycardia) 1
• Patients requiring adenosine for arrhythmia management 3