AMINOPHYLLINE

Aminophylline has a narrow therapeutic index, therefore cautious dosage determination is essential. Therapeutic serum concentrations of theophylline are considered to range from 10 to 20 micrograms/ml and levels greater than 20 micrograms/ml are often associated with toxic effects.

A range of 5 to 15 micrograms/ml may be effective, and associated with fewer adverse effects. The dosage should be titrated for each individual and adjusted with caution. Serum theophylline levels should be monitored to ensure that they remain within the therapeutic range.

During therapy, patients should be monitored carefully for signs of toxicity. Elimination of theophylline in children younger than 6 months of age, especially in neonates, appears to be reduced. Because of this variation in metabolism the use of Aminophylline injection in children under 6 months of age is not recommended.

Use in patients NOT currently receiving theophylline preparations To minimise adverse effects, IV Aminophylline should be administered slowly, at a rate not exceeding 25mg Aminophylline per minute, up to a dose of 250-500mg (5mg/kg).

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. b. The use of Aminophylline IV in children under 6 months of age is not recommended.

3mg/kg/hour Use in patients currently receiving theophylline preparations In patients who are currently receiving theophylline preparations, the time, route of administration and dosage form of the patient’s last dose should be determined where possible and considered in determining a loading dose.

5mg/kg (lean body weight) of theophylline will result in a 1 microgram/ml increase in serum theophylline concentration. Therefore, in patients currently receiving theophylline preparations, the loading dose should be deferred until a serum theophylline concentration can be attained or the clinician must carefully select a dose based on the potential benefits and risks.

Subsequently, the approximate IV aminophylline maintenance doses described above may be considered. Method of administration Aminophylline 25 mg/ml solution for injection/infusion may be given by slow intravenous injection or intravenous infusion in glucose injection or sodium chloride injection.

Adverse events are usually a consequence of gastrointestinal irritation, stimulation of the central nervous system and effects on the cardiovascular system. Hypotension, arrhythmias and convulsions may follow intravenous injection, particularly if the injection is too rapid, and sudden deaths have been reported.

Severe toxicity may occur without preceding milder symptoms (see also

2). Aminophylline has a narrow therapeutic index and serum levels should be monitored regularly, particularly during initiation of therapy. Aminophylline injection should be administered cautiously to patients over 55 years of age. Children are particularly susceptible to the effects of theophylline and care is required when administrating aminophylline to children.

There have been reports of seizures in children with theophylline plasma levels within the accepted therapeutic range. Alternative treatment should be considered in patients with a history of seizure activity and, if Aminophylline Injection is used in such patients, they should be carefully observed for possible signs of central stimulation.

Caution is also advised in patients undergoing influenza immunisation or who have active influenza infection or acute febrile illness. Aminophylline should be given with caution to patients with cardiac failure, chronic obstructive pulmonary disease, renal or hepatic dysfunction and in chronic alcoholism since clearance of Aminophylline is decreased.

Because the mean half-life of theophylline is shorter in smokers than in non- smokers, the former group may require larger doses of aminophylline. During regular therapy serum potassium levels must be monitored. This is essential during combination therapy with beta2-agonists, corticosteroids or diuretics, or in the presence of hypoxia.

Aminophylline should be used with caution in patients with peptic ulcer, hyperthyroidism, glaucoma, diabetes mellitus, severe hypoxaemia, hypertension, compromised cardiac or circulatory function and epilepsy, as these conditions may be exacerbated.

Methylxanthines may increase gastric acidity and care should be taken when they are used in patients with a history of peptic ulceration Aminophylline should not be administered concurrently with other xanthine medications.

1. Aminophylline should not be administered concomitantly with other xanthine drugs. When therapeutic doses of Aminophylline and/or theophylline are administered simultaneously by more that one route or in more than one preparation, the hazard of serious toxicity is increased.

The use of Aminophylline IV in children under 6 months of age is not recommended. The use of Aminophylline is contraindicated in patients with acute porphyria.