Aminophylline Administration Rate
Aminophylline should be administered intravenously over 20-30 minutes when given as a loading dose of 6 mg/kg diluted in 100-200 mL of IV fluid, or as a 250-mg IV bolus for acute atrioventricular block associated with inferior myocardial infarction. 1, 2
Loading Dose Administration
For specific clinical scenarios requiring aminophylline loading doses:
- Post-heart transplant bradycardia: Administer 6 mg/kg in 100-200 mL of IV fluid over 20-30 minutes 1, 2
- Spinal cord injury with symptomatic bradycardia: Administer 6 mg/kg in 100-200 mL of IV fluid over 20-30 minutes 1, 2
- Second or third-degree AV block with acute inferior MI: Administer 250 mg IV bolus 1, 2
The FDA label specifies that a loading dose of 5.7 mg/kg aminophylline (equivalent to 4.6 mg/kg theophylline) administered over 30 minutes will produce a maximum post-distribution serum concentration averaging 10 mcg/mL (range 6-16 mcg/mL) 3
Maintenance Infusion Rates
After the loading dose, continuous infusion rates vary by patient population:
- Non-smoking adults: 0.5 mg/kg/hr as aminophylline (0.4 mg/kg/hr theophylline equivalent) 3
- Children (age 1-9 years): 1.0 mg/kg/hr as aminophylline (0.8 mg/kg/hr theophylline equivalent) 3
- Elderly patients (>60 years): Maximum 21 mg/hr as aminophylline (17 mg/hr theophylline equivalent) unless serum levels remain <10 mcg/mL and symptoms persist 3
Critical Safety Considerations
The 20-30 minute infusion time is essential to avoid toxicity. Rapid administration can cause serious adverse effects including arrhythmias, hypotension, and seizures 1, 3
Drug compatibility warnings:
- Never mix aminophylline with epinephrine HCl or isoproterenol HCl 2
- Avoid mixing with alkali-labile drugs including norepinephrine bitartrate 2
Monitoring requirements during administration:
- Continuous cardiac monitoring is essential during infusion 1
- Serum theophylline concentrations should be measured to guide dosing, as clearance rates vary widely between patients (adult clearance averages 0.64 ± 0.38 ml/kg/min) 4
- Target therapeutic serum concentration is 10-20 mcg/mL 1, 3
Special Population Adjustments
Dose reduction and slower infusion rates are required in:
- Elderly patients (clearance decreased by 30%) 3
- Hepatic insufficiency (clearance decreased by ≥50%) 3
- Congestive heart failure (clearance decreased by ≥50%) 3
- Neonates (very low clearance, 50% renal excretion of unchanged drug) 3
Common pitfall: Standardized dosing without monitoring produces variable and often excessive serum concentrations due to individual variation in drug clearance 4. The infusion rate must be adjusted based on serum theophylline levels rather than using fixed dosing schedules 4.