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Lab Manual for UCSF Clinical Laboratories

Lab Manual for SFGH

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Item Value
Available Stat? Yes
Test code AAP
Performed by? Chemistry
Sendout? no
Price range $$$
In House Availability Routine: 7 days;
STAT: 24 hours/ 7 days
Principle Acetaminophen is hydrolyzed to p-aminophenol followed by reaction with 8-hydroxyquinoline to form a colored compound.
Interpretation CLINICAL SIGNIFICANCE: Acetaminophen is one of the most common causes of overdose death in the prescription/over-the-counter drug category. Patients who present soon after ingestion with potentially life-threatening acetaminophen overdoses may exhibit few or nonspecific symptoms. The relatively benign antidote (n-acetyl-cysteine [Mucomystp(R)]) is very effective if given within 24-48 hrs of ingestion.

1. Determining the time of ingestion, measurement of a 4-hour-post-ingestion serum acetaminophen concentration and, in acute exposures, appropriate use of the Rumack-Matthew nomogram to guide management can prevent serious morbidity and mortality. Call the California Poison Control Center for guidance in the management of patients with possible acetaminophen overdose or elevated levels. Their number is 1-800-8POISON.

2. Patients may fail to provide a history of acetaminophen ingestion; the drug is widely available in combination with other agents in prescription and over-the-counter preparations.

3. Many clinicians routinely order acetaminophen levels in all overdose patients, regardless of the history.

4. The nomogram should not be used in chronic or repeat ingestions.

5. Ingestion of Tylenol Extended Relief or of drugs that delay gastric emptying may alter acetaminophen pharmacokinetics and therefore interpretation of the nomogram.

6. The risk of hepatotoxicity from acetaminophen is increased in patients who are malnourished, alcoholic, fasting, or taking drugs that induce P-450 activity.
Container type gel tube (gold or green top)
Amount to Collect 2 mL
Sample type Blood
Normal range The therapeutic range is 10-30 mg/L (66-199 mcmol/L). All values > 50 mg/L are considered Critical Values and are called to the physician or patient care unit immediately.

See Clinical Significance, below, for interpretation of acetaminophen concentrations and toxicity.
Synonyms Tylenol;
Stability 7 days at 2-8°C
Interferences The administration of N-acetylcysteine (NAC) for acetaminophen overdose will result in a negative bias for the acetaminophen measurement if NAC is present in the sample at concentrations greater than 200 mg/L.
References 1. Acetaminophen -SL Assay IN50510-4 June 6, 2001. Diagnostic Chemicals Ltd. Oxford, CT.

2. Glynn, J.P., Kendel S.E.: Lancet, pp 1147-48, May 17, 1975.

3. Ambre, J., Alexander, M.: JAMA, 238:500, 1977.

4. Sporer, K.A., and Khayam-Bashi, H. Acetaminophen and salicylate serum levels in patients with suicidal ingestion or altered mental status. Am. J. Emerg. Med. 1996; 14:443-446.

5. Fenton, J. The Laboratory and the Poisoned Patient: A Guidebook for Interpreting Laboratory Data. AACC Press, Washington, D.C., 1998.

6. Lacy, C. F., Armstrong, L.L., Goldman, M. P., Lance L.L, Drug Information Handbook 7th Ed., 1999-2000, Lexi-Comp Inc., Hudson, OH., 1999, p. 20-21.

7. Olson KR ed. Poisoning & Drug Overdose, 4th ed. Clinical Manual. McGraw-Hill, 2004, p. 66-69.

CPT coding 82003
Last Updated 7/1/2015 2:20:41 PM
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