Aminophylline Intravenous for Adults

Who can administer

May be administered by registered competent doctor or nurse/midwife

Important information

• Loading dose only given if patient not previously on oral theophylline or aminophylline (but see Further information below)
• See monitoring requirements below
• To avoid excessive dosage in obese patients, dose should be calculated on the basis of ideal body weight for height (patient is obese if actual body weight is 20% or more above ideal body weight or BMI > 30) ^{(ref 1)}
• There are numerous important interactions - check latest BNF
• For Y-site compatibility see below

Available preparations

Aminophylline 250mg per 10ml ampoule

Reconstitution

Already in solution

Draw up using a 5 micron filter needle

Infusion fluids

Sodium Chloride 0.9% or Glucose 5%

Methods of intravenous administration

Intermittent intravenous infusion (loading dose only) ^{(ref 2)}

• Add required dose to 100ml infusion fluid and give over at least 20 minutes
• Maximum recommended rate 25mg/minute
• Fluid restricted: can be administered undiluted ^{(ref 5)}

Continuous intravenous infusion (administer using an electronically controlled infusion device)

• Add required dose to a suitable volume of infusion fluid e.g. 500mg to 500ml = 1mg/ml
• Administer at a rate as per 'dose' below
• Fluid restricted: can be administered undiluted ^{(ref 5)}

Dose in adults

Usual dose

Loading dose first (if appropriate)

• Loading doses must NOT be given to patients already taking oral theophylline or aminophylline (but see Further information below)
• Doses should be based on ideal body weight for height - see Important information
• Give 6mg per kg (usually 250 to maximum 500mg), followed by maintenance dose.
• If patient experiences acute adverse reactions while loading dose is being given, the infusion may be stopped for 5 to 10 minutes, or administered at a slower rate ^{(ref 3)}

Maintenance dose

• Doses should be based on ideal body weight for height - see Further information

Patient	Maintenance dose FIRST 12 hours	Maintenance dose BEYOND first 12 hours
Healthy, NON-smokers	0.7mg/kg/hour	0.5mg/kg/hour - adjusted according to plasma theophylline concentrations
ELDERLY patients	0.6mg/kg/hour	0.3mg/kg/hour - adjusted according to plasma theophylline concentrations
Congestive HEART FAILURE/LIVER FAILURE	0.5mg/kg/hour	0.1 to 0.2mg/kg/hour - adjusted according to plasma theophylline concentrations
SMOKERS	Often higher maintenance doses are required (ref 6)

Monitoring

• The half-life is variable (range 7 to 9 hours) (non-smoking, otherwise healthy asthmatic patient)
• The half-life may be prolonged or reduced in other disease states - for examples see maintenance dose table above
• Monitor potassium - may cause hypokalaemia
• Monitor ECG, heart rate and blood pressure ^{(ref 2)}
• Desired levels: 10 to 20 microgram/mL ^{(ref 3)}
• Adverse drug reactions may occur within the range of 10 to 20mg/L. Levels above 20mg/L are more likely to be associated with adverse effects
• Take serum level 30 minutes after the loading dose has been given ('post-loading dose level')
• Start the continuous infusion once the loading dose is complete, and recheck level after 12 hours- (to determine if levels are increasing or decreasing from post-loading dose level)
• Monitor levels regularly and adjust dose according to levels and adverse effects

Further information

• Loading doses: Ideally the loading dose would be deferred until serum theophylline levels are known. If this is not possible, and if the clinical situation requires that the drug be given, a dose of 3.1mg/kg of aminophylline may be considered, on the basis that it is likely to increase the serum theophylline concentration by about 5 mcg/L when administered as a loading dose
• Note: while the loading dose may be administered by slow IV injection- it must be given over 20 minutes- so for practicality, it is best to administer as a short infusion instead
• Patients on intravenous aminophylline need careful monitoring and nursing attention
• Rapid administration has been associated with acute hypotension, arrhythmias and convulsions
• Concurrent use of other xanthine derivatives are contraindicated due to the risk of toxicity
• Each 0.5mg/kg aminophylline administered as a loading dose gives rise to a 1mcg/ml increase in serum concentrations of theophylline
• Patient is obese if actual body weight is 20% or more above ideal body weight or BMI > 30 ^{(ref 1)}

  Ideal body weight (IBW) calculations

  • Male 50kg + (2.3 x inches over 5 feet) or 50kg + (0.9 x cm over 152 cm)

  • Female 45.5kg + (2.3 x inches over 5 feet) or 45.5kg + (0.9 x cm over 152 cm)

Storage

Store below 25⁰C

References

1: Sanford guide to antimicrobial therapy - online v 7.0.3 ^{(information on obesity extrapolated from data on antimicrobials)}

2: Injectable medicines guide Medusa, accessed online 26/03/2025

3: SPC Mercury pharmaceuticals October 2020

4: Uptodate: accessed 27/03/2025

5. Minimum infusion volumes, UKCPA, 2012

6. Martindale- accessed online 27/03/2025

Therapeutic classification

Bronchodilator - Theophylline