What is the recommended intravenous (IV) dose of aminophylline?

Aminophylline IV Dosing

For acute severe asthma in adults, administer a loading dose of 5-6 mg/kg aminophylline IV over 20-30 minutes (omit if patient already on theophylline), followed by a continuous infusion of 0.5 mg/kg/hr, with the goal of achieving a therapeutic serum theophylline concentration of 10-20 mcg/mL. 1, 2

Loading Dose Administration

Standard Loading Dose (Theophylline-Naive Patients)

• Administer 5-6 mg/kg aminophylline IV over 20-30 minutes for patients who have not received theophylline in the previous 24 hours 1, 2
• This loading dose produces an average post-distribution serum theophylline concentration of 10 mcg/mL (range 6-16 mcg/mL) 2
• The 20-30 minute infusion time is critical to avoid toxicity including arrhythmias, hypotension, and seizures 3
• Calculate dose based on ideal body weight, not total body weight, as theophylline distributes poorly into body fat 2

Patients Already on Theophylline

• Do NOT give a loading dose without first obtaining a serum theophylline level if the patient has received any theophylline in the previous 24 hours 2
• If a loading dose is necessary after measuring the serum level, calculate as: Loading Dose = (Desired concentration - Measured concentration) × 0.5 L/kg 2
• Use a conservative target concentration of 10 mcg/mL to account for variability in volume of distribution 2

Maintenance Infusion Rates

Adults (Non-Smoking)

• Start continuous infusion at 0.5 mg/kg/hr aminophylline (equivalent to 0.4 mg/kg/hr theophylline) immediately after the loading dose 2
• This produces an average steady-state concentration of 10 mcg/mL (range 7-26 mcg/mL) 2

Pediatric Patients (Age 1-9 Years)

• Administer loading dose of 5-6 mg/kg over 20 minutes, followed by continuous infusion of 1.0 mg/kg/hr aminophylline 1, 2
• Children have higher theophylline clearance than adults, requiring higher maintenance doses 2
• Research shows that 72% of pediatric patients had subtherapeutic levels within 5.5 hours of standard loading, with 78% requiring additional bolus doses, suggesting close monitoring is essential 4

High-Risk Populations Requiring Dose Reduction

• In patients with cor pulmonale, cardiac decompensation, liver dysfunction, or those taking drugs that reduce theophylline clearance (e.g., cimetidine), do not exceed 21 mg/hr aminophylline unless serum concentrations can be monitored at 24-hour intervals 2
• Theophylline clearance is decreased by 50% or more in patients with hepatic insufficiency or congestive heart failure 2
• Elderly patients (>60 years) have 30% decreased clearance compared to young adults 2

Specific Clinical Indications

Second or Third-Degree AV Block with Acute Inferior MI

• Administer 250 mg aminophylline as a single IV bolus 1, 3

Post-Heart Transplant or Spinal Cord Injury with Bradycardia

• Administer 6 mg/kg aminophylline in 100-200 mL IV fluid over 20-30 minutes 1, 3

Acute Severe Asthma (Alternative Dosing from British Guidelines)

• For small patients: 750 mg/24 hours continuous infusion 1
• For large patients: 1500 mg/24 hours continuous infusion 1
• Monitor blood concentrations if continued for over 24 hours 1

Monitoring Requirements

Timing of Serum Level Checks

• Obtain first serum theophylline level 30 minutes after loading dose to assess need for additional loading and guide continuing therapy 2
• Obtain second level one expected half-life after starting continuous infusion (approximately 4 hours in children age 1-9,8 hours in non-smoking adults) 2
• If level is declining, administer additional loading dose and/or increase infusion rate 2
• If level is rising above target, decrease infusion rate before concentration exceeds 20 mcg/mL 2
• Obtain additional samples at 12-24 hours, then at 24-hour intervals for ongoing adjustments 2

Target Therapeutic Range

• Maintain serum theophylline concentration between 10-20 mcg/mL 3, 2
• Concentrations >20 mcg/mL are considered toxic 5
• In high-risk patients, steady-state may require 5 days to achieve 2

Critical Safety Considerations

Administration Precautions

• Always administer loading dose over 20-30 minutes, never as rapid IV push 1, 3, 2
• Continuous cardiac monitoring is essential during infusion 3
• Use ideal body weight for dose calculations in obese patients 2

Common Pitfalls to Avoid

• Never assume a patient has not taken theophylline based on history alone - always obtain a serum level if there is any uncertainty 2
• Research demonstrates that half-loading doses (3 mg/kg) in patients reporting recent theophylline use resulted in 23.2% developing toxic levels, indicating the unreliability of patient history 5
• Nonlinearity of elimination may begin at concentrations <10 mcg/mL in some patients, so make dose adjustments in small increments 2
• Patients with very high initial clearance rates have the greatest likelihood of experiencing large changes in serum concentration with dose changes 2

Drug Incompatibilities

• Do not mix aminophylline with epinephrine HCl, isoproterenol HCl, or norepinephrine bitartrate due to compatibility concerns 3