What is the recommended dose of aminophylline for adults and children?

Aminophylline Dosing Guidelines

For adults, administer a loading dose of 5-6 mg/kg aminophylline (equivalent to 4.6 mg/kg theophylline) IV over 20-30 minutes, followed by a continuous infusion of 0.5 mg/kg/hr; for children, use the same loading dose of 5-6 mg/kg over 20 minutes followed by a maintenance infusion of 1 mg/kg/hr. 1, 2, 3

Loading Dose Administration

Adults

• Administer 5-6 mg/kg aminophylline IV over 20-30 minutes for patients who have not received theophylline in the previous 24 hours 2, 3
• This loading dose will produce a target serum theophylline concentration of approximately 10 mcg/mL (range 6-16 mcg/mL) 3
• Always infuse over 20-30 minutes—never as a rapid IV push—to avoid serious toxicity including arrhythmias, hypotension, and seizures 2
• For patients already on oral theophylline, obtain a serum theophylline level before administering any loading dose 3, 4

Children

• Administer 5 mg/kg aminophylline IV over 20 minutes for life-threatening bronchospasm in children 1, 2
• Omit the loading dose if the child is already receiving oral theophyllines 1
• The same loading dose produces similar serum concentrations in children aged 1-9 years as in adults 3

Special Circumstances: Patients Already on Theophylline

• Do not give a loading dose before obtaining a serum theophylline concentration if the patient has received any theophylline in the previous 24 hours 3
• If a loading dose is necessary, calculate it using: D = (Desired C - Measured C) × 0.5 L/kg, where the desired concentration should be conservative (e.g., 10 mcg/mL) 3
• A serum concentration obtained 30 minutes after the loading dose can guide subsequent dosing 3

Maintenance Infusion Dosing

Adults

• Initiate continuous infusion at 0.5 mg/kg/hr aminophylline (equivalent to 0.4 mg/kg/hr theophylline) immediately after the loading dose 2, 3
• This will achieve a steady-state concentration of approximately 10 mcg/mL (range 7-26 mcg/mL) 3
• For acute severe asthma, the British Thoracic Society recommends 750 mg/24 hours for small patients and 1500 mg/24 hours for large patients 2

Children

• Initiate continuous infusion at 1 mg/kg/hr aminophylline (equivalent to 0.8 mg/kg/hr theophylline) after the loading dose 1, 2, 3
• This produces similar steady-state concentrations as in adults 3

High-Risk Patients

• 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 (17 mg/hr theophylline) unless serum concentrations can be monitored at 24-hour intervals 3
• These patients may require 5 days to reach steady-state 3

Clinical Decision Algorithm for Acute Bronchospasm

Aminophylline should only be considered for bronchospasm resistant to optimal first-line therapy 1, 2:

1. Confirm adequate first-line therapy has been given: high-flow oxygen, nebulized β-agonist (salbutamol 5 mg or terbutaline 10 mg), and systemic corticosteroids 1, 2
2. If patient is still not improving after 15-30 minutes, add ipratropium 0.5 mg (100 mcg in children) to nebulizer and increase β-agonist frequency to every 15-30 minutes 1, 2
3. Only if life-threatening features persist (PEF <33% predicted, silent chest, cyanosis, exhaustion, altered consciousness), then administer aminophylline 1, 2

Monitoring Requirements

Initial Monitoring

• Obtain a serum theophylline concentration one expected half-life after starting the infusion (approximately 4 hours for children age 1-9,8 hours for nonsmoking adults) to determine if concentration is accumulating or declining 3
• If the level is declining, administer an additional loading dose and/or increase the infusion rate 3
• If the level is rising, decrease the infusion rate before it exceeds 20 mcg/mL 3

Ongoing Monitoring

• Obtain additional samples at 12-24 hours, then at 24-hour intervals to adjust for changes 3
• Monitor serum theophylline concentrations if the infusion continues beyond 24 hours 2
• Continuous cardiac monitoring is essential during infusion 2
• Target therapeutic serum theophylline concentration is 10-20 mcg/mL 2

Critical Safety Considerations

Dosing Based on Body Weight

• Calculate all doses based on ideal body weight, not total body weight, as theophylline distributes poorly into body fat 3

Dose Adjustments

• Make dose increases or decreases in small increments due to nonlinear elimination kinetics that can begin at serum concentrations <10 mcg/mL 3
• Patients with very high initial clearance rates have the greatest likelihood of experiencing large changes in serum concentration with dosage changes 3

Special Populations Requiring Dose Reduction

• Elderly patients (>60 years): theophylline clearance is decreased by 30% compared to young adults 3
• Neonates: clearance is very low, and approximately 50% of the dose is excreted unchanged in urine (vs. 10% in older children and adults) 3
• Hepatic insufficiency: clearance is decreased by 50% or more 3
• Congestive heart failure: clearance is decreased by 50% or more 3

Drug Interactions

• Do not mix aminophylline with alkali-labile drugs including norepinephrine bitartrate, epinephrine HCl, or isoproterenol HCl 2

Common Pitfalls to Avoid

• Never administer the loading dose as a rapid IV push—always infuse over 20-30 minutes to prevent serious toxicity 2
• Never give a loading dose without checking a serum level first if the patient has taken theophylline within 24 hours 3
• Do not assume standard dosing will work for all patients—72% of pediatric patients receiving a 6 mg/kg loading dose had subtherapeutic concentrations within 5.5 hours, and 78% required additional bolus doses 5
• Do not use aminophylline as first-line therapy—it should only be used when bronchospasm is resistant to nebulized β-agonists and systemic corticosteroids 1, 2
• Do not forget to adjust for high-risk populations—patients with liver disease, heart failure, or on interacting medications require significantly lower doses 3