Aminophylline

Narrow therapeutic index - cautious dosage determination is essential; titrate for each individual, monitor serum theophylline levels and watch for signs of toxicity. Approximate IV aminophylline maintenance doses from the SPC table: children 6 months to 9 years 1 mg/kg/hour; children 10-16 years of age and young adult smokers 0.8 mg/kg/hour; otherwise healthy non-smoking adults 0.5 mg/kg/hour; elderly patients 0.3 mg/kg/hour. If patients experience acute adverse effects while loading doses are being infused, the infusion may be stopped for 5-10 minutes or administered at a slower rate. In patients ALREADY receiving theophylline preparations: determine the time, route, dosage form and dose of the last dose where possible; loading doses are based on the expectation that 0.5 mg/kg (lean body weight) of theophylline will result in a 1 microgram/ml increase in serum theophylline concentration; the loading dose should be deferred until a serum theophylline concentration can be attained, or the clinician must carefully select a dose based on potential benefits and risks - the maintenance doses above may then be considered. Administer cautiously to patients over 55 years of age. Serum potassium must be monitored during regular therapy, especially with beta-2 agonists, corticosteroids or diuretics, or in the presence of hypoxia. Smokers have a shorter theophylline half-life and may require larger doses. US labelling (DailyMed, cross-check only - not the UK SPC) expresses doses as theophylline with aminophylline equivalents, e.g. a loading dose of 4.6 mg/kg theophylline (5.7 mg/kg as aminophylline) over 30 minutes and a non-smoking adult infusion of 0.4 mg/kg/hr theophylline (0.5 mg/kg/hr as aminophylline); do not mix the two labelling conventions.

SPC section 4.2 maintenance table: children 6 months to 9 years 1 mg/kg/hour; children 10-16 years of age (and young adult smokers) 0.8 mg/kg/hour. The use of aminophylline IV in children under 6 months of age is NOT recommended - elimination of theophylline in children younger than 6 months, especially neonates, appears to be reduced (also listed under section 4.3). The SPC does not give an age-separated loading dose; the loading dose stated for patients not already on theophylline is 250-500 mg (5 mg/kg) at a rate not exceeding 25 mg/minute. Children are particularly susceptible to the effects of theophylline and care is required; seizures have been reported in children with theophylline plasma levels within the accepted therapeutic range (section 4.4). Verify all paediatric dosing against a children's formulary and local guidance before administration.