Methadone Peak Level, Serum or Plasma

CPT: 80299
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Synonyms

  • Dolophine®
  • Methadose®

Special Instructions

This test is intended for therapeutic monitoring only.


Expected Turnaround Time

3 - 6 days


Related Documents


Specimen Requirements


Specimen

Serum or plasma


Volume

1 mL


Minimum Volume

0.3 mL


Container

Red-top tube, lavender-top (EDTA) 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.


Storage Instructions

Refrigerate.


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


Test Details


Use

Monitor therapeutic levels of methadone.


Methodology

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


Additional Information

Methadone possesses many of the pharmacologic properties of morphine and is approximately equipotent as an analgesic when administered parenterally. Unlike morphine, however, methadone produces marked sedative effects with repeated administration as a result of drug accumulation. This undesirable property restricted clinical usage of the drug until 1965 when Dole and Nyswander began narcotic maintenance treatment of former heroin addicts using large daily oral doses of dl-methadone.1 Whereas maintenance patients may receive as much as 180 mg of the drug daily, doses of ≤50 mg have been known to prove fatal to nontolerant adults. The pharmacologic activity is due almost entirely to the l-isomer. The d-methadone isomer does have analgesic properties in large doses and this may be due to conversion to minor amounts of α-1-methadone and α-1-normethadol, both of which are potent analgesics. Methadone can be detected in blood 15 to 45 minutes after oral administration, with peak levels occurring at 2.5 to 4 hours. The elimination of half-life has a mean value of approximately 22 hours (range 5 to 130 hours). Due to interindividual variation of P450 enzyme systems, a 17-fold variation in methadone blood concentrations can be found in patients given the same dose.2 The rate-of-change ratio between peak and trough SML measures can be a more clinically useful guide, and it has been suggested that the peak SML should be more than twice the trough level.3


Footnotes

1. Drug Information Handbook. 24th ed. Hudson, OH: Wolters Kluwer Clinical Drug Information, Inc; 2015; 1311-1315.
2. Eap CB, Buclin T, Baumann P. Interindividual variability of the clinical pharmacokinetics of methadone: Implications for the treatment of opioid dependence. Clin Pharmacokinet. 2002; 41(14):1153-1193.
3. US Department of Health and Human Services, Substance Abuse and Mental Health Services Administration Center for Substance Abuse Treatment. A National Assessment of Methadone-associated Mortality; Background Briefing Report. Rockville, Md: SAMHSA; 2004:16.

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
007784 Methadone Peak Level, Serum 007783 Methadone Peak Level, Serum ng/mL 3772-1

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