Aminophylline

Aminophylline [1 vial $2.59]

ADMINISTRATION ROUTES:

  • IV

ALTERNATIVE NAMES:

  • Aminophylline (DBL)

ICU INDICATIONS:

  1. Management of acute life-threatening asthma (particularly in children)

PRESENTATION AND ADMINISTRATION:

  • IV:
    250mg/10ml (solution). For adult administration dilute 500mg in 500ml of compatible IV fluid to make a concentration of 1mg/ml.
    Store at room temperature 15-30°C; protect from light
    Compatible with:
    normal saline, D5W, D10W, Glucose and Sodium chloride, Hartmann’s.
    Do not mix with other medications – many medications with precipitate if mixed with aminophylline.

DOSAGE:

  • Asthma and COPD:
    IV aminophylline is very rarely used for treatment in asthma or COPD in adults in our Intensive Care Unit. The dilution when used for adults is 500mg in 500ml of compatible IV fluid (ie 1mg/ml) at 0.5-1mg/kg/hr (usually 0-40ml/hr). Dose adjustment for obesity
    Theophylline does not distribute into fatty tissue. Dosage should be calculated on the basis of lean (ideal) body weight.
    Note: Do not use standard dosing for IV infusion if the patient is already on oral theophylline; dosage should be worked out after determining the serum concentration.

DOSAGE IN RENAL FAILURE AND RENAL REPLACEMENT THERAPY:

  • While dose adjustment in renal failure is possible, dosage is complex and the risk of toxicity is high. Aminophylline should be ceased if the patient develops significant renal impairment.

DOSAGE IN PAEDIATRICS:

  • Aminophylline Infusion in Life threatening asthma
    Dose if patient aged 1 – 9 years:
    1.1 mg/kg/hour
    Add 55 mg/kg of IV aminophylline solution (25 mg/ml) to a 50 ml syringe and make up to 50ml with 5% dextrose
    Then infuse at 1 ml/hr
    Dose if patient aged 10 – 15 years and weight < 35 kg:
    0.7 mg/kg/hour
    Add 35 mg/kg of IV aminophylline solution (25 mg/ml) to a 50 ml syringe and make up to 50ml with 5% dextrose
    Then infuse at 1 ml/hr
    Dose if patient aged 10 – 15 years and weight > 35 kg
    0.7 mg/kg/hour
    Draw up neat IV Aminophylline solution (25 mg/ml) into a 50 ml syringe
    Then infuse at 0.028 ml/kg/hr
    For example if you have a 40 kg child then infusion rate will be 40 x 0.028 = 1.12 ml/hr
    Dose adjustment for obesity
    Theophylline does not distribute into fatty tissue. Dosage should be calculated on the basis of lean (ideal) body weight. Use the 50th percentile of expected weight for age

    Note: Do not use standard dosing for IV infusion if the patient is already on oral theophylline; dosage should be worked out after determining the serum concentration.

CLINICAL PHARMACOLOGY:

  • Aminophylline is a 2:1 complex of theophylline and ethylenediamine. The activity is of theophylline alone. Theophylline directly relaxes the smooth muscle of the bronchial airway and pulmonary blood vessels, thus acting mainly as a bronchodilator and smooth muscle relaxant. It has also been demonstrated that aminophylline has a potent effect on diaphragmatic contractility in normal persons and may then be capable of reducing fatigability and therapy improve contractility in patients with chronic obstructive airway disease. The exact mode of action remains unsettled.

CONTRAINDICATIONS:

  1. Hypersensitivity to either aminophylline o rethylenediamine.
  2. Active peptic ulcer disease
  3. Underlying seizure disorders (unless receiving appropriate anticonvulsant medications).

WARNINGS

  • In individuals in whom theophylline plasma clearance is reduced for any reason, even conventional doses may result in increased serum levels and potential toxicity. Reduced theophylline clearance has been documented in the following readily identifiable groups:
    (1) patients with impaired liver function;
    (2) patients over 55 years of age, particularly males and those with chronic lung disease;
    (3) those with cardiac failure from any cause;
    (4) patients with sustained high fever;
    (5) neonates and infants under 1 year of age; and
    (6) those patients taking certain drugs (see DRUG INTERACTIONS).
  • Serious side effects such as ventricular arrhythmias, convulsions or even death may appear as the first sign of toxicity without any previous warning. A serum concentration measurement is the only reliable method of predicting potentially life-threatening toxicity. Theophylline products may cause or worsen arrhythmias and any significant change in rate and/or rhythm warrants measurement of a serum level and consideration of cessation of the drug.

PRECAUTIONS

  • General:
    See WARNINGS
  • Laboratory Tests:
    Spec Collection: SST (Yellow) or Plain (Red); Paediatric and Neonatal only: 0.4 mL green microtainer
    Therapeutic Range: 55-110 umol/L Neonates: 35-70 umol/L.
    Sampling Time: IV infusion: anytime after 12 hours on infusion.
  • Drug/Laboratory Test Interactions:
    Acetazolamide interferes with the HPLC method of assay for theophylline. Interference with the theophylline assay by acetazolamide depends on the solvent used in the extraction; acetazolamide may not interfere with other assay methods for theophylline

IMPORTANT DRUG INTERACTIONS FOR THE ICU

  • Aminophylline With:
    Allopurinol (high-dose): Increased serum theophylline levels
    Ciprofloxacin: Increased serum theophylline levels
    Erythromycin: Increased serum theophylline levels
    Lithium carbonate: ncreased renal excretion of lithium
    Oral contraceptives: Increased serum theophylline levels
    Phenytoin: Decreased theophylline and phenytoin serum levels
    Propranolol: Increased serum theophylline levels
    Rifampin: Decreased serum theophylline levels
    Increased toxicity may be seen with combinations of high dose beta agonists and aminophylline.

ADVERSE REACTIONS

  • Body as a Whole:
    Irritability, restlessness, insomnia
  • Cardiovascular System:
    Palpitation, tachycardia, extrasystoles, flushing, hypotension, circulatory failure, ventricular arrhythmias.
  • Respiratory System:
    Tachypnoea.
  • Digestive System:
    Nausea, vomiting, epigastric pain, haematemesis, diarrhoea.
  • Nervous System:
    Headaches, reflex hyperexcitability, muscle twitching, clonic and tonic generalized convulsions.

Critical Care Drug Manual

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