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HelpTest Code LAB35 Theophylline Level
Clinical Information
Coadministration of cimetidine and erythromycin will significantly inhibit theophylline clearance, requiring dosage reduction. Other drugs such as allopurinol, ciprofloxacin, oral contraceptives, and propranolol inhibit theophylline clearance to a lesser degree. Smoking induces the synthesis of cytochrome P448, the antipyrine-dependent cytochrome, which significantly increases the rate of metabolism of theophylline. Drugs such as phenobarbital, phenytoin, carbamazepine, and rifampin slightly increase the rate at which the drug is cleared.
Synonym
- THEO
Specimen Required
Preferred Container/Tube: Mint Green Top
Acceptable Container/Tube: Mint Green Top, Red Top
Specimen Volume: 3 mL
Specimen Minimum Volume: 1 mL
Specimen Stability Information
Ambient: 4 hours
Refrigerated: 30 days
Specimen Collection Information
Processing instructions: Draw PRIOR to dose.
Rejected Due To
- Gross hemolysis
- Gross icterus
- Quantity not sufficient
- Quality not acceptable
Reference Values
Therapeutic Range: 5.0-20.0 mcg/mL
Method Description
Based on competition between drug in the sample and drug labeled with the enzyme glucose-6-phosphate dehydrogenase (G6PDH) for antibody binding sites. Enzyme activity decreases upon binding to the antibody, so the drug concentration in the sample can be measured in terms of enzyme activity. Active enzyme converts oxidized nicotinamide adenine dinucleotide (NAD) to NADH, resulting in an absorbance change that is measured spectrophotometrically.
Performing Lab
Clinical Lab UH
Day(s) Performed
Monday through Sunday
Report Available
Same day/1 day
Reporting Name
Theophylline
CPT Code Information
80198
LOINC Code Information
4049-3