What is the proper administration protocol for an aminophylline (theophylline) drip in asthma?

Aminophylline Drip Administration Protocol for Asthma

For patients with severe or life-threatening asthma who have not responded to first-line treatments, administer intravenous aminophylline as a loading dose of 5.7 mg/kg over 20 minutes (equivalent to 4.6 mg/kg of theophylline), followed by a continuous infusion of 0.5 mg/kg/hr in non-smoking adults or 1.0 mg/kg/hr in children aged 1-9 years. 1, 2

Indications for Aminophylline Use

• Aminophylline should be considered only if progress is unsatisfactory after initial treatments with nebulized β-agonists, systemic corticosteroids, and nebulized ipratropium 1
• Reserved for patients with life-threatening features or those who fail to improve with first-line therapies 1
• Not recommended as first-line therapy due to narrow therapeutic window and potential for toxicity 3, 4

Pre-Administration Assessment

• Check if patient is already taking oral theophyllines - DO NOT give bolus aminophylline to these patients 1
• Obtain baseline serum theophylline level if patient has received any theophylline in previous 24 hours 2
• Assess for conditions requiring dose adjustment:
  • Elderly patients (>60 years) - reduce dose by 30% 2
  • Liver dysfunction - reduce dose by 50% 2
  • Congestive heart failure - reduce dose by 50% 2
  • Children and neonates require special dosing considerations 2

Administration Protocol

Loading Dose

• For patients who have not received theophylline in previous 24 hours:
  • Administer 5.7 mg/kg aminophylline (4.6 mg/kg theophylline) over 20 minutes 1, 2
  • Use ideal body weight for calculation in obese patients 2

Maintenance Infusion

• Non-smoking adults: 0.5 mg/kg/hr aminophylline (0.4 mg/kg/hr theophylline) 2
• Children (1-9 years): 1.0 mg/kg/hr aminophylline (0.8 mg/kg/hr theophylline) 2
• Reduce initial infusion rate to maximum of 21 mg/hr in patients with:
  • Cor pulmonale
  • Cardiac decompensation
  • Liver dysfunction
  • Concurrent use of drugs that reduce theophylline clearance (e.g., cimetidine) 2

Monitoring During Treatment

• Measure serum theophylline concentration 30 minutes after completing loading dose 2
• Obtain second level at one expected half-life after starting infusion:
  • Approximately 8 hours for non-smoking adults
  • Approximately 4 hours for children aged 1-9 years 2
• Target serum concentration: 10-15 mcg/mL 2, 3
• Continue to monitor peak expiratory flow and clinical response 1
• Watch for signs of toxicity: nausea, vomiting, tachycardia, arrhythmias, seizures 3, 4

Dose Adjustment

• If serum level is declining (due to higher clearance):
  • Consider additional loading dose and/or increase infusion rate 2
• If serum level is rising (due to accumulation):
  • Decrease infusion rate before concentration exceeds 20 mcg/mL 2, 3
• Obtain additional samples at 12-24 hour intervals to make further adjustments 2

Common Pitfalls and Caveats

• Relying solely on weight-based formulas without monitoring serum levels can lead to dangerous overdosing - 34% of patients may develop toxic levels >20 mg/L 5
• Avoid administering aminophylline to patients already on oral theophyllines without checking levels first 1, 3
• Aminophylline adds toxicity but may not improve efficacy when added to high-dose inhaled β-agonists 4
• Smokers have increased theophylline clearance and may require higher maintenance doses 2
• The narrow therapeutic window requires careful monitoring to avoid toxicity while maintaining efficacy 3

Remember that aminophylline is not a first-line treatment for asthma exacerbations but should be reserved for cases where standard treatments with nebulized β-agonists, systemic corticosteroids, and ipratropium have failed to produce adequate improvement 1.