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aminophylline

aminophylline

introduction

  • aminophylline is a one of the methylxanthines groupd of medications along with theophylline and caffeine.
  • 400 mg theophylline is equivalent to 500 mg aminophylline
  • ampoules: 250 mg /10 mL
  • therapeutic serum levels: 55-110 umol/L (10-20 mcg/mL)
  • each 1.25 mg/kg aminophylline results in a plasma theophylline increase of approximately 11 umol/L (2 mcg/mL)
  • it's main usage is in severe asthma in extremis or not responding to iv salbutamol, and thus generally should be used in a resuscitation cubicle or similar with ECG monitoring
  • it must be given in a separate iv line to iv salbutamol
  • if the patient is not already taking theophylline, an iv loading dose is given.
  • patients who have taken theophylline containing preparations in past 24 hours need the loading dose reduced by 50% or not given.
  • elimination rates (and thus maintenance infusion dose needed), is dependent on age, weight, smoking status, hepatic function (and thus also cardiac function)

precautions

  • Not suitable for IM admin; CHF; cardiac, renal, hepatic, circulatory impairment; cor pulmonale; acute pulmonary oedema, febrile illness, myocardial injury; hypertension; chronic alcoholism; pneumonia; influenza (incl vaccination); hyper/ hypothyroidism; hypertension; tachyarrhythmia; gastroesophageal reflux; angina; epilepsy; peptic ulcer; diabetes; glaucoma; COPD; rapid IV admin; elderly, pregnancy, lactation, children esp premature, neonates

adverse effects

  • rapid IV administration may result in hypotension, syncope, cardiac arrest, and death
  • serious arrhythmias and convulsions may occur at levels greater than 193 umol/L (35 mcg/mL) and are often NOT preceded by less serious signs of toxicity

compatibility

  • incompatible with amiodarone, corticotropin, diltiazem, dobutamine, epinephrine, hyaluronidase, hydralazine, hydroxyzine, insulin, isoprenaline, levorphanol, meperidine, norepinephrine, ondansetron, prochlorperazine, verapamil, salbutamol
  • compatible with magnesium sulphate, morphine, metoclopramide, methylprednisolone, potassium chloride, propofol, heparin

administration

RCH and Western Health preparation and administration procedure

preparation of infusion
  • add 25mg/kg aminophylline to 5% dextrose to make total of 50mls = 0.5mg/kg/ml
loading dose
  • 10mg/kg (max. 500mg) over 1 hour = 20ml/hr if weight < 50kg, otherwise 500mg/(0.5mg/kg x weight in kg) ml/hr
maintenance infusion
  • age 1-9 years:
    • rate = 1.1mg/kg/hr = 2.2ml/hr if using 0.5mg/kg/ml infusion as above
  • age 10 yrs and over:
    • rate = 0.7mg/kg/hr = 1.4ml/hr if using 0.5mg/kg/ml infusion as above

pharmacokinetic approach

iv loading dose
  • 6mg/kg over 30min
  • ie. Vd x 10mg/L theophylline and Vd = 0.5L/kg lean body mass
iv maintenance dose
  • Clearance x 10mg/L theophylline
  • Clearance = 0.041 L/kg/h in normal adults but variable → monitor serum levels
  • Clearance higher in children = 0.06-0.9 L/kg/h
    • BUT neonates & infants have the SLOWEST CLEARANCE

other dosing regimes

maintenance dose
  • children 9-12yrs: 0.8mg/kg/hr
  • children 12-16yrs: smokers: 0.8mg/kg/hr non-smokers: 0.6mg/kg/hr
  • adults:
    • smokers: 0.8mg/kg/hr
    • non-smokers: 0.5mg/kg/hr
    • impaired liver or cardiac function: 0.25mg/kg/hr1)
aminophylline.txt · Last modified: 2009/03/10 19:40 (external edit)