Aminophylline is a xanthine which is most often used it the treatment of severe acute asthma.
- loading dose - this is omitted if the patient has been receiving previous treatment with theophylline or aminophylline. The aminophylline should be administered by slow i.v. over 20 minutes at a dosage of 5 mg/kg, although in practice, a loading dose of 250 mg is given for most adults.
- maintenance dose - give by infusion at 0.5 - 1.0 mg/kg/hour. It is important to monitor theophylline levels (18 hours after starting the infusion) and the dose should be adjusted to maintain the level within the therapeutic range of 10-20 mg/l. If the patient has previously been on theophylline or aminophylline then the levels should be taken on admission.
- for maintenance infusion, add 1g (1000 mg) to 1L (1000 ml) normal saline to give a solution of 1 mg/ml. Adjust the rate to body weight accordingly; for example, for a 70 kg adult, the infusion rate would be 35-70 mls/hour.
Side effects of aminophylline include:
- abdominal pain, nausea, headache, tremor, insomnia and palpitations, convulsions and cardiac arrhythmias.
Various drugs affect the half-life of theophylline:
- increased half-life is seen in heart failure, cirrhosis, viral infections, and drugs e.g. erythromycin, ciprofloxacin, cimetidine.
- decreased half-life is seen in heavy drinkers, smokers, and by drugs e.g. barbiturates, phenytoin, carbamazepine, rifampicin.
Check summary of product characteristics before prescribing this drug.