What is the typical dose for an aminophylline (theophylline) infusion?

Aminophylline Infusion Dosing

For acute bronchospasm or bradycardia, administer a loading dose of 5-6 mg/kg aminophylline IV over 20-30 minutes (never as rapid push), followed by a continuous infusion of 0.5-1 mg/kg/hour, with dose adjustments based on patient factors and therapeutic drug monitoring. 1, 2

Loading Dose Administration

Standard Loading Dose Protocol

• Theophylline-naive patients: Administer 5-6 mg/kg aminophylline IV over 20-30 minutes 1, 2
• Patients on recent theophylline: Reduce loading dose to 3 mg/kg if theophylline was taken within 12 hours (short-acting) or 24 hours (sustained-release) 3
• Never administer as rapid IV push - the 20-30 minute infusion time is essential to avoid serious toxicity including arrhythmias, hypotension, and seizures 1

Specific Clinical Indications

• Acute severe asthma (adults): 5-6 mg/kg IV over 20-30 minutes, only if patient remains unresponsive after 15-30 minutes of optimal nebulized beta-agonists and systemic corticosteroids 1
• Acute severe asthma (children): 5 mg/kg IV over 20 minutes 1
• Second or third-degree AV block with acute inferior MI: 250 mg IV bolus 4, 1
• Post-heart transplant or spinal cord injury bradycardia: 6 mg/kg in 100-200 mL IV fluid over 20-30 minutes 1

Critical Pre-Loading Considerations

• Always obtain serum theophylline level before loading if patient has taken any theophylline in the previous 24 hours 2
• Calculate dose based on ideal body weight for obese patients, as theophylline distributes poorly into body fat 2
• A serum concentration obtained 30 minutes after loading (when distribution is complete) guides subsequent dosing 2

Maintenance Infusion Dosing

Standard Maintenance Rates

• Non-smoking adults: 0.4 mg/kg/hour (0.5 mg/kg/hour as aminophylline) 2
• Children age 1-9 years: 0.8 mg/kg/hour (1.0 mg/kg/hour as aminophylline) 2
• Elderly patients (>65 years): 0.4 mg/kg/hour 4
• Patients with liver/cardiac disease: 0.4 mg/kg/hour 4

High-Risk Patient Populations

In patients with cor pulmonale, cardiac decompensation, liver dysfunction, or taking drugs that reduce theophylline clearance (e.g., cimetidine), the initial infusion rate should not exceed 17 mg/hour theophylline (21 mg/hour aminophylline) unless serum concentrations can be monitored at 24-hour intervals. 2

• These patients may require 5 days to reach steady-state 2
• Maximum daily dose should not exceed 400 mg/day in high-risk patients unless serum levels indicate need for higher doses 2

Therapeutic Drug Monitoring Algorithm

Initial Monitoring

1. Obtain serum level 30 minutes after loading dose to assess distribution and guide further loading if needed 2
2. Obtain second level one expected half-life after starting infusion:
   • Children age 1-9: approximately 4 hours 2
   • Non-smoking adults: approximately 8 hours 2
3. If level is declining: Patient has higher than average clearance - consider additional loading dose and/or increase infusion rate 2
4. If level is rising: Decrease infusion rate before concentration exceeds 20 mcg/mL 2

Ongoing Monitoring

• Obtain additional samples at 12-24 hours, then at 24-hour intervals during maintenance infusion 1, 2
• Target therapeutic range: 10-20 mcg/mL 1, 2
• For neonatal apnea, target lower range of 7.5 mcg/mL 2
• Continuous cardiac monitoring is essential during infusion 1

Dose Adjustment Based on Serum Levels

The FDA label provides specific guidance for adjusting maintenance infusion rates based on measured serum theophylline concentrations, though exact adjustment algorithms should follow institutional protocols and the detailed tables in the drug label 2.

Critical Safety Considerations

Administration Precautions

• Do not mix aminophylline with other drugs in the same syringe - add separately to IV solution 2
• Avoid mixing with alkali-labile drugs including epinephrine HCl, norepinephrine bitartrate, isoproterenol HCl, and penicillin G potassium 2
• When giving aminophylline "piggyback," turn off the existing IV system if admixture incompatibility is a concern 2

Common Pitfalls to Avoid

• Never use total body weight for obese patients - always calculate based on ideal body weight 2
• Do not assume therapeutic levels in patients reporting recent theophylline use - always measure pre-load level to avoid toxicity 5
• Recognize that aminophylline is only 80% theophylline - when converting doses, aminophylline dose = theophylline dose ÷ 0.8 2

Signs Requiring Immediate Dose Reduction

• Presence of adverse effects (nausea, vomiting, tachycardia, tremor) 2
• Sustained fever or other physiologic changes that reduce clearance 2
• Addition or discontinuation of interacting drugs 2

Clinical Context for Use

Aminophylline should be reserved for severe cases unresponsive to first-line therapy. 1 For acute asthma, confirm the patient has received adequate treatment with high-flow oxygen, nebulized beta-agonists, and systemic corticosteroids before considering aminophylline 1. The British Thoracic Society guidelines emphasize this should only be used "if patient is still not improving" after 15-30 minutes of optimal bronchodilator therapy 1.