Aminofilin Retard

Disease of the cardiovascular system (e.g. an adjunct in the treatment of pulmonary oedema or paroxysmal nocturnal dyspnoea caused by left ventricular heart failure), reversible airways obstruction including status asthmaticus and acute bronchospasm.

Aminofilin Retarde Injection BP may be given by slow intravenous injection or intravenous infusion in glucose injection or sodium chloride injection.

Aminofilin Retarde has a narrow therapeutic index, therefore cautious dosage determination is essential. Therapeutic serum concentrations of theophylline are considered to range from 10 to 20 mcg/ml and levels greater than 20 mcg/ml are often associated with toxic effects. A range of 5 to 15 mcg/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 Aminofilin Retarde injection in children under 6 months of age is not recommended.

Use in patients NOT currently receiving theophylline preparations

To minimise adverse effects, IV Aminofilin Retarde should be administered slowly, at a rate not exceeding 25mg Aminofilin Retarde 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.

Approximate IV Aminofilin Retarde Maintenance Doses

n.b. The use of Aminofilin Retarde IV in children under 6 months of age is not recommended.

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. Loading doses are based on the expectation that 0.5mg/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 Aminofilin Retarde maintenance doses described above may be considered.

Aminofilin Retarde injection should not be used in patients hypersensitive to ethylenediamine or those allergic to the theophyllines, caffeine or theobromine.

Aminofilin Retarde should not be administered concomitantly with other xanthine drugs. When therapeutic doses of Aminofilin Retarde 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 Aminofilin Retarde IV in children under 6 months of age is not recommended.

The use of Aminofilin Retarde is contraindicated in patients with acute porphyria.

Intravenous Aminofilin Retarde must be administered very slowly to prevent dangerous central nervous system and cardiovascular side-effects due to direct stimulating effect of Aminofilin Retarde.

Aminofilin Retarde has a narrow therapeutic index and serum levels should be monitored regularly, particularly during initiation of therapy.

Aminofilin Retarde 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 Aminofilin Retarde 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 Aminofilin Retarde 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.

Aminofilin Retarde 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 Aminofilin Retarde is decreased.

Theophylline clearance may be increased in smokers and in those regularly exposed to tobacco smoke.

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.

Aminofilin Retarde 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.

Aminofilin Retarde should not be administered concurrently with other xanthine medications.

None known.

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

Immune system disorders:

Hypersensitivity reactions (see also Skin and subcutaneous tissue disorders).

Metabolism and nutrition disorders:

Metabolic disturbances such as hypokalaemia, hypophosphataemia, and hyponatraemia may occur.

Nervous system/Psychiatric disorders:

Headache, insomnia, confusion, restlessness, hyperventilation, anxiety, vertigo/dizziness, tremor. Higher doses may lead to maniacal behaviour, delirium and convulsions.

Eye disorders:

Visual disturbances.

Cardiac disorders:

Palpitations, tachycardia, cardiac arrhythmias, hypotension.

Gastrointestinal disorders:

Nausea, vomiting, abdominal pain, diarrhoea, gastro-oesophageal reflux, gastrointestinal bleeding.

Skin and subcutaneous tissue disorders:

Rash, maculo-papular rash, erythema, pruritus, urticaria, exfoliative dermatitis.

General/Administration site reactions:

Higher doses may result in hyperthermia and extreme thirst.

Reporting of suspected adverse reactions

Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme at: www.mhra.gov.uk/yellowcard.

Aminofilin Retarde has a narrow therapeutic index. Theophylline toxicity is most likely to occur when serum concentrations exceed 20 micrograms/ml and becomes progressively more severe at higher serum concentrations.

Fatalities in adults have occurred during IV Aminofilin Retarde administration in large doses in patients with renal, hepatic or cardiovascular complications or where the injection has been given rapidly.

Symptoms

Tachycardia, in the absence of hypoxia, fever or administration of sympathomimetic drugs, may be an indication of theophylline toxicity.

Gastro-intestinal symptoms:

Anorexia, nausea, vomiting, diarrhoea, and haematemesis.

Neurological symptoms:

Restlessness, insomnia, irritability, headache, agitation, hallucinations, extreme thirst, slight fever, dilated pupils, and tinnitus. Seizures may occur even without preceding symptoms of toxicity and often result in death. Coma may develop in very severe cases.

Cardiovascular symptoms:

Palpitations, arrhythmias, hypotension, supraventricular and ventricular arrhythmias may occur.

Metabolic symptoms:

Hypokalaemia can develop rapidly and may be severe. Hyperglycaemia, albuminuria, hyperthermia, hypomagnesaemia, hypophosphataemia, hypercalcaemia, respiratory alkalosis and metabolic acidosis may also occur. Rhabdomyolysis may also occur.

Treatment

Treatment of overdosage is supportive and symptomatic. Serum theophylline and potassium levels should be monitored. Repeated oral administration of activated charcoal enhances the elimination of theophylline from the body even after intravenous administration. Aggressive antiemetic therapy may be required to allow administration and retention of activated charcoal.

Seizures may be treated with IV diazepam 0.1-0.3mg/kg up to 10mg. Restoration of fluid and electrolytes balance is necessary. Hypokalaemia should be corrected by intravenous infusion of potassium chloride. Sedation with diazepam may be required in agitated patients.

Propranolol may be administered intravenously to reverse extreme tachycardia, hypokalaemia and hyperglycaemia provided the patient does not suffer from asthma.

In general, theophylline is metabolised rapidly and haemodialysis is not warranted. In patients with congestive heart failure or liver disease, haemodialysis may increase theophylline clearance by as much as 2-fold.

Charcoal haemoperfusion should be considered if:

- Ileus/ intestinal obstruction prevents administration of multiple dose activated charcoal.

- Plasma theophylline concentration > 80mg/L (acute) or > 60mg/L (chronic). In infants under 6 months of age or the elderly, charcoal haemoperfusion should be considered at theophylline concentrations >40 mg/L. Clinical features rather than theophylline concentration are the best guide for treatment.

Aminofilin Retarde is a soluble derivative of theophylline and is given for its theophylline activity. Aminofilin Retarde relaxes smooth muscle and relieves bronchial spasm. It stimulates the myocardium and reduces venous pressure in congestive heart failure, leading to a marked increase in cardiac output. It has stimulant effect on respiration, and also a diuretic action of short duration.

None stated.

No further information other than that which is included in the Summary of Product Characteristics.

Aminofilin Retarde injection is not stable in solutions having a pH of substantially less than 8, however, the drug appears to be relatively stable in large volume parenteral solutions over a wide pH range (3.5-8.6) if Aminofilin Retarde concentrations do not exceed 40mg per ml. The activity of alkali-sensitive drugs will be reduced by Aminofilin Retarde, these drugs should not be added to IV fluids containing Aminofilin Retarde.

Use as directed by a physician.