aminophylline
Table of Contents
aminophylline
see also:
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
- see methylxanthines
- 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 08:40 by 127.0.0.1