Aminophylline is the combination of theophylline with ethylenediamine and is more soluble than theophylline alone. It is used in the management of acute severe asthma and COPD. Therapeutic range for bronchodilation is 10-20 mg/L Theophylline is metabolised by the liver.

The plasma theophylline concentration is increased in heart failure, cirrhosis, viral infections, in the elderly, and by drugs that inhibit its metabolism, such as; clarithromycin, erythromycin, ciprofloxacin. Plasma theophylline concentration is decreased in smokers, in chronic alcoholism and by drugs that induce its metabolism, such as rifampicin. Consult list of interactions (Appendix A in the BNF ). Theophylline may have an additive effect when used in combination with beta2-agonists; the combination may increase the risk of side–effects, including hypokalaemia.

Side Effects: Nausea, vomiting, gastric irritation, diarrhoea, urticaria, erythema, exfoliative dermatitis. Tachycardia, palpitations and hypotension may accompany administration, monitor heart rate and blood pressure. Arrhythmias and convulsions may occur if infusion rate is too fast.

If the patient already takes oral theophylline or aminophylline, measure serum theophylline prior to starting a maintenance infusion and omit the loading infusion. If a patient does not take any oral theophylline or aminophylline preparation a loading infusion is required before commencing a maintenance regime. The dose is calculated based on patient’s weight: 5mg/Kg This is added to 100 mls N/Saline and administered over 30 mins

To avoid excessive dosage in obese patients, dose should be calculated on the basis of ideal body weight (IBW) for height.

IBW = [males 50kg, females 45kg] + 2.3kg per inch over 5ft

During loading, all patients should be attached to cardiac monitoring.

A serum theophylline level should be taken after 6 hours, 18 hours and then every 24 hours there after.

This is given following a loading dose OR as initial treatment in patients already receiving oral theophylline treatment

In patients already receiving oral theophylline treatment a serum theophylline level should be taken before commencement of the maintenance infusion.

Maintenance dosing in patients UNDER 70 years

Maintenance infusion should be started at a rate of 0.5 mg/kg/hour

Add 1g Aminophylline to 1000mls 0.9% Normal Saline (1mg/ml) and run the infusion at the following flow rate

Maintenance dosing in patients of 70 years or over

This should be initiated after the loading dose is given at a rate of 0.3mg/kg/hour. Dilute 500mg aminophylline in 500mls sodium chloride 0.9% (1mg/ml).

All patients that require IV Aminophylline should be referred to and reviewed by a member of the Respiratory Team.

Following review by a respiratory consultant, patients who are stable after 24 hours of starting an aminophylline infusion can be taken off cardiac monitoring. Serum theophylline levels should be taken every 24 hours.

Hameln Pharma Ltd. Summary of product characteristic. Aminophylline Injection BP. Date of last revision August 2022. Aminophylline Injection BP - Summary of Product Characteristics (SmPC) - (emc) (medicines.org.uk) accessed 02/02/2024

This guideline has been registered with the Trust. However, clinical guidelines are guidelines only. The interpretation and application of clinical guidelines will remain the responsibility of the individual clinician. If in doubt, contact a senior colleague or expert. Caution is advised when using guidelines after the review date. This guideline is for use in Frimley Health NHS Foundation Trust hospitals only. Any use outside this location will not be supported by the Trust and will be at the risk of the individual using it.

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