Amikacin, Peak

CPT: 80150
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Test Details

Synonyms

  • Amikin®

Use

Amikacin is used to treat serious infections caused by susceptible aerobic gram-negative bacilli (eg, a number of the Enterobacteriaceae, P aeruginosa). Such infections include bacteremias; intra-abdominal, soft tissue (including burns), bone or joint, lower respiratory tract, and complicated urinary tract infections, and meningitis.

The major advantage of amikacin is its superior resistance profile. Thus, it is the aminoglycoside of choice for infections caused by aerobic gram-negative bacilli that are known or suspected to be resistant to other aminoglycosides. It should be the aminoglycoside of choice for general use in hospitals where the prevalence of resistance to gentamicin and tobramycin is known to be high or when there is concern about gentamicin- and tobramycin-resistant gram-negative bacilli in a particular clinical situation.

Because amikacin is the only currently available aminoglycoside effective against many gentamicin- and tobramycin-resistant organisms, many infectious disease experts have felt that its use should be restricted to minimize the emergence of additional resistant strains; however, there is no evidence that such restriction has delayed the emergence of resistance. Furthermore, reports from hospitals that rely on amikacin as the primary aminoglycoside suggest that resistance to amikacin does not increase despite widespread use and gentamicin/tobramycin resistance actually may decrease. Nevertheless, general use of amikacin in hospitals without a gentamicin or tobramycin resistance problem remains controversial. Amikacin is considerably more expensive than gentamicin, an important consideration in a cost-conscious environment.

Methodology

Immunoassay (IA)

Reference Interval

Therapeutic: peak: 20.0−30.0 μg/mL, trough: 1.0−8.0 μg/mL

Critical Value

Potentially toxic: peak: >30.0 μg/mL, trough: >8.0 μg/mL

Additional Information

Amikacin is cleared by the kidney and accumulates in renal tubular cells. Nephrotoxicity is most closely related to the length of time that trough levels are >8 μg/mL. Creatinine levels should be monitored every two to three days as an indicator of impending renal toxicity. The initial toxic result is nonoliguric renal failure that is usually reversible if the drug is discontinued. Continued administration of amikacin may produce oliguric renal failure. Nephrotoxicity may occur in as many as 10% to 25% of patients receiving aminoglycosides; most of this toxicity can be avoided by monitoring levels and adjusting dosing schedules accordingly.

Aminoglycosides may also cause irreversible ototoxicity that manifests itself clinically as hearing loss. Aminoglycoside ototoxicity is relatively uncommon and clinical trials in which levels were carefully monitored and dosing adjusted failed to show a correlation between auditory toxicity and plasma aminoglycoside levels. In situations in which dosing is not adjusted, however, sustained high levels may be associated with ototoxicity. This association is far from clear cut, and new once-daily dosing regimens (and associated high peak serum concentrations) that fail to enhance toxicity further complicate this issue.

Specimen Requirements

Specimen

Serum or plasma

Volume

1 mL

Minimum Volume

0.3 mL

Container

Red-top tube or green-top (heparin) tube. Do not use a gel-barrier tube. The use of gel-barrier tubes is not recommended due to slow absorption of the drug by the gel. Depending on the specimen volume and storage time, the decrease in drug level due to absorption may be clinically significant.

Collection

Transfer separated serum or plasma to a plastic transport tube. Both peak and trough concentrations should be monitored. The trough sample is drawn immediately prior to the next dose. Peak samples should be drawn 60 minutes after an IM injection, 30 minutes after the end of a 30-minute IV infusion, or immediately after a 60-minute IV infusion.

Storage Instructions

Room temperature

Stability Requirements

Temperature

Period

Room temperature

14 days

Refrigerated

14 days

Frozen

14 days

Freeze/thaw cycles

Stable x3

Causes for Rejection

Gel-barrier tube; severe hemolysis; lipemia; icteric specimen

Clinical Information

Special Instructions

Peak levels should be ordered with test 007204. Trough levels should be ordered using test 007205. Peak and trough levels may be ordered together as a profile on the same test request form using test 717330. Please label tubes appropriately as “peak” and “trough.”

References

AMA, Division of Drugs and Toxicology, Drug Evaluations Subscription, Chicago, IL: American Medical Association, Winter 1993.
Anhalt JP, Brown SD. High-performance liquid chromatographic assay of aminoglycoside antibiotics in serum. Clin Chem. 1978 Nov; 24(11):1940-1947. 709826
Dito W. Aminoglycosides and therapeutic drug monitoring. In: Baer D, Dito W, eds.Interpretations in Therapeutic Drug Monitoring. Chicago, Ill: American Society of Clinical Pathologists;1982:187-204, 235-252.

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
007204 Amikacin Peak, Serum 3319-1 007204 Amikacin Peak, Serum ug/mL 3319-1
Reflex Table for Amikacin Peak, Serum
Order Code Order Name Result Code Result Name UofM Result LOINC
Reflex 1 007000 See below: 007000 See below: N/A

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