METHADONE
Classification
Methadone is a narcotic analgesic which is approximately equipotent to that of morphine. Methadone has been utilized to treat opioid dependency and prescribed as a heroin substitute in methadone maintenance programs since the 1960's. Typically, daily oral dosing with doses up to 180 mg/day is prescribed with efficacy measured by the absence of withdrawl symptoms. Dosing is then gradually decreased until opiate dependency is eliminated.
Metabolism
Methadone is metabolized primarily to two pharmacologically inactive metabolites, EDDP and EMDP. Monitoring for the presence of EDDP (methadone metabolite) is a means to determine compliance to methadone treatment. The elimination half-life of methadone is approximately 15-55 hours with about 5-50% of a dose eliminated as methadone and 3-25% as EDDP. Large individual variations in elimination do occur due to urine pH, urine volume, dose, rate of metabolism, drug interaction, etc.
| DETECTION LIMITS | ||||||||||||||
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| Results Reporting |
Detection Limits (mcg/mL) |
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| Chemical Name | Trade Name | EIA | TLC | EIA | TLC | GC/MS | ||||||||
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| Methadone | Dolophine | + | + | 0.3 | 0.5 | 0.1 | ||||||||
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| Levomethadyl (LAAM) * |
ORLAAM | + + |
- | 0.3 | N/A | N/A | ||||||||
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| Methadone Metabolite | + | + | 0.3 | 0.5 | 0.1 | |||||||||
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*The EIA method for methadone will detect LAAM at high concentrations. LAAM is quickly metabolized, therefore parent LAAM will not always be detected.
NOTE: Some individuals metabolize methadone at increased rates and may test negative for both methadone and methadone metabolite.
| SCREENING & CONFIRMATION CUT-OFF LEVELS BY PROCEDURE | ||||||
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| Methadone | Methadone Metabolism |
Interpretation | ||||
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| + | + | Methadone was ingested due to presence of metabolite. | ||||
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| - | + | Methadone ingested due to presence of metabolite; Parent methadone below testing detection limit. | ||||
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| + | - | Methadone ingested and metabolite below detection limit; or if creatinine is 0.0 (water) then methadone, was poured directly into urine; or if creatinine is present then methadone. may have been poured into an alternate urine specimen. | ||||
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| - | - | Methadone was not ingested; or methadone and methadone metabolite were below the detection limit. GCMS can be utilized to increase sensitivity. | ||||
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Drug information data is not definitive and should be used for reference guidelines only.