Theophylline & Caffeine

Other names: Phylloconti; Aminophylline; Uniphyllin; Nuelin; Slo-Phyllin

This test measures the levels of theophylline and caffeine in the blood. Theophylline and caffeine are methylxanthines, which are substances that both relax and stimulate breathing. Theophylline is a medication which is given to children with asthma and adults with chronic obstructive pulmonary disease (COPD).

Why is the test used?

The test is used to monitor the levels of either theophylline or caffeine in the blood; the test is useful for doctors to adjust the dosage of medication to ensure the best possible results.

The test may also be ordered when a patient has symptoms associated with theophylline toxicity, including nausea, tremors, low blood pressure, fast heart rate and abdominal pain.

A caffeine test may be ordered when a newborn baby has symptoms of excessive caffeine levels in the blood, including irritability, tremors, restlessness, fits and rapid heart rate. The test may also be used on premature babies who do not respond as expected when given a treatment.

How is the test performed?

The test is done using a sample of blood, which is collected from a vein in the arm. A needle is inserted into the vein and the blood is collected in a syringe. Once the sample has been collected, it will be bottled, sealed, labelled with the patient’s name and sent away to the laboratory for analysis.

For infants, the blood may be taken from the heel; a needle will be used to prick the heel and the blood will be collected in a sample bottle.

What do the test results show?

Low levels of caffeine or theophylline may indicate that the dosage of the medication is too low; recommended concentrations for theophylline when used as a bronchodilator are between 10 and 20 mg/dl; levels above 20 mg/dl are thought to be toxic. The levels of caffeine for treating premature babies should be between 6 and 13 mg/dl.

Specific Blood Tests

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