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Homogeneous Immunoassays—Therapeutic Drug Monitoring
QMS®—Latex Enhanced Immunoturbidimetric Assays
Theophylline Assay System
The THEOPHYLLINE Assay System is intended for the quantitative determination of total theophylline in serum for therapeutic drug monitoring.
Theophylline is a methylxanthine used to treat bronchospasm, including asthma, and obstructive airway disease.1,2 Its effectiveness as a bronchodilator agent overrides the low margin of safety between its effective therapeutic level and the onset of toxicity symptoms.1
Theophylline is completely and rapidly absorbed from the gastro-intestinal tract, with an oral dose being absorbed in one hour and peak plasma concentrations being achieved in two hours.3-5 The drug is widely distributed in body fluids. In plasma about forty percent is protein bound.6 Theophylline is eliminated from the body via several parallel pathways. Approximately ten percent is eliminated unchanged by the kidneys, while the remainder is metabolized, apparently in the liver, largely to uric acid derivatives and 3-methylxanthine.2,6-8
Theophylline has a narrow therapeutic index with a range for serum levels from 10-20ug/ml.6,9,10 Individualized dosing and routine serum level monitoring are necessary for patients receiving theophylline, due to wide variation in theophylline absorption, metabolism and clearance.6,9,10
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