Lab Test

Theophylline Level

Aminophylline, Theodur, Slo-phyllin, Theophylline Level, Serum

Test Codes

EPIC: LAB5419, Beaker: THEO, Antrim: 17140



Specimen Collection Criteria

Collect (preferred specimen): One plain Red-top tube. (Minimum Whole Blood: 1.0 mL)
Also acceptable (not preferred): One Gold-top SST tube.

See Minimum Pediatric Specimen Requirements for Microtainer® collection.
Time of Collection: Peak, 2 hours post oral dosing.
Record the exact time of specimen collection on the tube or in the computer system.

Physician Office/Draw Specimen Preparation

Let specimens clot 30-60 minutes and refrigerate (2-8°C or 36-46°F) the collection tube within two hours of collection. (Minimumm: 1.0 mL blood)

Preparation for Courier Transport

Transport: Collection tube, refrigerated (2-8°C or 36-46°F). (Minimum: 1.0 mL blood)

Rejection Criteria

Severely lipemic or hemolyzed specimens. 

In-Lab Processing

Let specimens clot 30-60 minutes. Centrifuge specimen to separate serum from cells. Deliver an aliquot of serum or the collection tube immediately to the appropriate testing station.


Specimen Stability for Testing:

Collection Tubes
Room Temperature (20-26°C or 68-78.8°F): 24 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): Unacceptable

Serum Specimens (Pour-Overs)
Room Temperature (20-26°C or 68-78.8°F): 24 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): 3 months

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 7 days


Dearborn Chemistry Laboratory
Royal Oak Automated Chemistry Laboratory 



Sunday – Saturday, 24 hours a day.
STAT results available within 1 hour of receipt in the Laboratory.
Routine results available within 24 hours.

Reference Range

Therapeutic Range: 10-20 mcg/mL.
Critical Range: Greater than 25 mcg/mL.

Test Methodology

Enzyme Immunoassay.


Theophylline metabolism may be increased by infections and metabolic inducers such as Phenytoin and Phenobarbital. Its metabolism may be decreased by metabolic inhibitors such as Erythromycin.

Clinical Utility

Theophylline is a naturally occurring compound with bronchodilator effects. It is used in the treatment of bronchospasm associated with bronchial asthma, chronic bronchitis and pulmonary emphysema. This assay is used to monitor the therapeutic drug level and evaluate the toxicity of theophylline. Due to the drug's narrow therapeutic range and the wide personal variation in the rate of metabolism and clearance, essentially every patient taking theophylline should have their serum levels monitored.

CPT Codes



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