Aminophylline IV

How it works

It produces bronchodilation through non-selective phosphodiesterase inhibition and adenosine receptor antagonism, increasing intracellular cyclic AMP in airway smooth muscle.

Prescribing in practice

• It has a narrow therapeutic index and the intravenous loading dose must be omitted or reduced in patients already taking oral theophylline to avoid life-threatening toxicity such as seizures and arrhythmias.
• Clearance is altered by many factors and drugs (for example reduced by ciprofloxacin, macrolides and in heart failure or liver disease; increased by enzyme inducers), requiring dose adjustment.
• Give the loading dose as a slow intravenous infusion, as rapid administration can cause arrhythmias and profound hypotension.

Monitoring

Monitor ECG, serum potassium and theophylline concentrations, watching for tachyarrhythmia, hypokalaemia and signs of toxicity.

Counselling the patient

• Always ask about current oral theophylline before any loading dose.
• Report palpitations, nausea, tremor or agitation promptly as toxicity markers.
• Combination with beta-agonists increases the risk of hypokalaemia.

Evidence & guidelines

Intravenous aminophylline is positioned as a second-line adjunct in BTS/SIGN and NICE acute asthma guidance after first-line bronchodilators and steroids.