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Test Code CAFN Caffeine, Serum

Useful For

Monitoring therapy in neonates


Assessing toxicity in neonates

Method Name

Enzyme Multiplied Immunoassay Technique (EMIT)

Reporting Name

Caffeine, S

Specimen Type


Specimen Required

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Specimen Volume: 0.5 mL

Collection Instructions:

1. Serum gel tubes should be centrifuged within 2 hours of collection.

2. Red-top tubes should be centrifuged and aliquoted within 2 hours of collection.

Specimen Minimum Volume

0.25 mL

Specimen Stability Information

Specimen Type Temperature Time
Serum Refrigerated (preferred) 72 hours
  Frozen  28 days
  Ambient  72 hours

Reject Due To


Mild OK; Gross reject







Clinical Information

Caffeine is used to treat apnea that occurs in newborn infants, the most frequent complication seen in the neonatal nursery.


Caffeine is administered orally (nasogastric tube) as a loading dose of 3 mg/kg followed by a maintenance dose of 1 mg/kg administered once every 24 to 48 hours, depending on the patient's response and the serum level.


In neonates, caffeine has a half-life that ranges from 20 to 100 hours, which is much longer than in adults (typically 4-6 hours) due to the immaturity of the neonatal liver. This requires that small doses be administered at much longer intervals than would be predicted based on adult pharmacokinetics.


The volume of distribution of caffeine is 0.6 L/kg and the drug is approximately 35% protein bound.


Toxicity observed in neonates is characterized by central nervous system and skeletal muscle stimulation and bradycardia. These symptoms are seen in adults at lower levels than in neonates, suggesting that neonates have much greater tolerance to the drug.

Reference Values

Therapeutic: 8.0-20.0 mcg/mL

Critical value: ≥30.0 mcg/mL


Optimal pharmacologic response occurs when the serum level is in the range of 8.0 to 20.0 mcg/mL.


Toxicity in neonates and adults may be seen when the serum level is >20.0 mcg/mL.

Clinical Reference

Ou CN, Frawley VL: Concurrent measurement of theophylline and caffeine in neonates by an interference-free liquid-chromatographic method. Clin Chem 1983;29:1934-1936

Day(s) and Time(s) Performed

Monday through Sunday; Continuously

Analytic Time

Same day/1 day

Performing Laboratory

Mayo Medical Laboratories in Rochester

Test Classification

This test has been cleared or approved by the U.S. Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
CAFN Caffeine, S 3422-3


Result ID Test Result Name Result LOINC Value
CAFN Caffeine, S 3422-3