Indomethacin (Indocin), Serum

CPT CODE:

USEFUL FOR:

Monitoring serum concentrations in neonates being treated with indomethacin to facilitate closure of PDA

SPECIMEN REQUIRED:

Draw blood in a plain, red-top tube(s). (Serum gel tube is not acceptable.) Spin down and send 0.5 mL of serum refrigerated.

TRANSPORT TEMPERATURE:

Refrig\Frozen OK\Ambient OK

CLINICAL INFORMATION:

Indomethacin is commonly used to treat newborns who have patentductus arteriosus (PDA).
Closure of PDA depends on maintaining a certain trough serum levelof indomethacin. The required trough concentration varies from child- to-child.
The appropriate level in a given child is determined by clinical response as well as by echocardiography of the ductus.      Indomethacin toxicity includes oliguria and necrotizing enterocolitis:  oliguria, rise in creatinine, and fluid retention may not appear for a day or two after administration. Necrotizing enterocolitis may not occur until a week or more following initiation of therapy.
Indomethacin half-lives and volumes of distribution in newbornpopulations can vary, respectively, over 3-fold and 20-fold ranges.
Depending upon the above parameters in a given newborn, poor closure may result from subtherapeutic levels. Toxicity may occur from elevated levels following administration of a standard dose.

CLINICAL INTERPRETATION:

Trough serum concentrations of indomethacin in the range of 1.0-2.0ug/mL have been shown to be adequate in approximately 50% of cases for achieving closure of PDA.
Ninety percent will close at levels above 2.0 ug/mL

REFERENCE VALUES:

Therapeutic concentration:  1.0-2.0 ug/mL

Toxic concentration: > or = 3.0 ug/mL