Serum theophylline measurement is used to determine and adjust drug dosage for optimal therapeutic effect as well as for drug toxicity evaluation.
Theophylline or aminophylline is a bronchodilator drug that belongs to methylxanthines and reduces the breakdown of intracellular cyclic adenosine monophosphate (cAMP), which in turn stimulates dilation of bronchial smooth muscle and relaxation of pulmonary blood vessels. However, this particular therapeutic effect does not occur until theophylline levels are very close to the peak of its therapeutic range. At lower levels, theophylline exhibits anti-inflammatory properties, allowing it to be used in place of steroid drugs. Intravenous theophylline is used in the acute phase of obstructive pulmonary disease. Theophylline is 60% bound to plasma proteins, has a half-life of 6-10 hours in adults and 2-5 hours in children (half-life is reduced by 40% in smokers). 90% of theophylline is metabolized in the liver. Steady-state levels occur in 15-20 hours in adults and 5-40 hours in children.
Theophylline toxicity includes arrhythmias, gastrointestinal bleeding, headaches, hypotension, nausea, anxiety, seizures, syncope, tachycardia, and vomiting.
Possible Interpretations of Pathological Values
- Increase: Congestive heart failure, chronic obstructive pulmonary disease, hepatic impairment, overdose. Medications: Allopurinol, cimetidine, ciprofloxacin, clindamycin, erythromycin, lincomycin, oral contraceptives, probenecid
- Decrease: Smoking. Medications: Barbiturates, carbamazepine, furosemide, isoniazid, nortriptyline, phenytoin, rifampicin. Natural remedies containing balsam (Hypericum perforatum).
Important Note
Laboratory test results are the most important parameter for the diagnosis and monitoring of all pathological conditions. 70%-80% of diagnostic decisions are based on laboratory tests. The correct interpretation of laboratory results allows a doctor to distinguish "healthy" from "diseased".
Laboratory test results should not be interpreted from the numerical result of a single analysis. Test results should be interpreted in relation to each individual case and family history, clinical findings, and the results of other laboratory tests and information. Your personal physician should explain the importance of your test results.
At Diagnostiki Athinon we answer any questions you may have about the test you perform in our laboratory and we contact your doctor to get the best possible medical care.
