Methylphenidate, Serum or Plasma

CPT: 80360
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Test Details

Synonyms

  • Ritalin®

Limitations

This test was developed and its performance characteristics determined by LabCorp. It has not been cleared or approved by the Food and Drug Administration.

Methodology

Liquid chromatography/tandem mass spectrometry (LC/MS-MS)

Reference Interval

Therapeutic: 5.0−20.0 ng/mL

Critical Value

Potentially toxic: >40.0 ng/mL

Additional Information

Methylphenidate is an oral central nervous system stimulant used to treat attention deficit hyperactivity disorders (ADHD) in children and ADD in adults. Methylphenidate is a derivative of phenethylamine, and its CNS actions are similar to the amphetamines. The exact mechanism of action is not fully understood. The drug is rapidly and well absorbed from the GI tract, achieving peak blood levels in 60 to 120 minutes. Some preparations of methylphenidate will exhibit a bimodal plasma concentration-time profile with half-lives varying from 2.5 to 8.4 hours1 and about 80% of a dose is excreted in the urine in 24 hours. The major metabolite, ritalinic acid (pharmacologically inactive), is formed by hydrolysis of the methyl ester linkage. This takes place enzymatically and nonenzymatically in alkaline conditions during storage of serum or plasma. The use of EDTA as an anticoagulant reduces hydrolytic loss. After a 0.3 mg/kg oral dose of methylphenidate, peak plasma concentrations typically do not go much above 20 ng/mL, but they can reach as high as 70 ng/mL on a higher dose of 0.6 mg/kg. The common side effects of methylphenidate are due mainly to its adrenergic activity, including insomnia, anorexia, headache, and tachycardia.

Specimen Requirements

Specimen

Serum or plasma, frozen

Volume

7 mL whole blood or 2 mL serum or plasma

Minimum Volume

1.1 mL

Container

Gray-top (sodium fluoride) tube, red-top tube,or green-top (heparin) tube

Collection

Separate serum or plasma and transfer to a plastic transport tube. Freeze and ship frozen. Collect specimen as a peak level one to two hours after dosing. To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested.

Storage Instructions

Freeze; do not refreeze.

Stability Requirements

Temperature

Period

Room temperature

Unstable

Refrigerated

Unstable

Frozen

6 months

Freeze/thaw cycles

Stable x1

Causes for Rejection

Gel-barrier tube; thawed specimen

Clinical Information

Footnotes

1. Markowitz JS, Straughn AB, Patrick KS, et al. Pharmacokinetics of methylphenidate after oral administration of two modified-release formulations in healthy adults. Clin Pharmacokinet. 2003; 42(4):393-401. 12648029

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
715300 Methylphenidate, Serum 3807-5 715301 Methylphenidate, S ng/mL 3807-5

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