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Drug Test Cutoff Levels, Detection Time Frames and Possible Cross-Reactive Substances, that could be cause of false positive drug test result.

 

Drug Class (In Bold) or targeted substance drugs of abuse to be Screened/Tested

Positive Initial Screen
Cutoff ng/mL for On-Site Urine or Saliva Drug Test

Confirmatory Test Cutoff ng/ml for Urine or Oral Fluid Drug Testing

Duration
of Detectability with Urine Drug Testing

These Substances Could be Cause of Preliminary Misleading or False Positive Results***

Amphetamines Drug Class

1,0001 500 2 (50) 2

amantadine, bupropion, chloroquine, chlorpromazine, desipramine, dextroamphetamine, ephedrine, fenfluramine, labetalol, mexiletine,
n-acetyl procainamide, phentermine, phenylephrine, phenylpropanolamine, propanolol, pseudoephedrine, quinacrine, ranitidine, selegiline, trazodone, tyramine

Amphetamine (AMP)

  500 1 250 2 (50) 2

2-4 days (20-50 hr)

Methamphetamine (MET)

  500 1 250 2 (50) 2

2 days (>24 hr)

MDMA (Ecstasy, XTC)

500 1,2 (50) 2 250 1,2 (50) 2

1.5-2 days

Barbiturates (BAR)

  • short-acting
  • intermediate
  • long-acting

300 3

200 3


1 day
2-3 days
7+ days (up to 30)

phenytoin

Benzodiazepines (BZD)

  • ultra-short-acting a
  • short-acting b
  • intermediate c
  • long-acting d

300 3

200 3


12 hours
1 day
~2-3 days
7+ days (up to 30)

oxaprozin, sertraline

Cannabinoids (THC)
(marijuana metabolite

  • light smoker
  • moderate (4x/wk)
  • heavy use (daily)
  • chronic heavy use

50 1,2 (4) 2

15 1,2 (2) 2

(4-10 hr)

Up to 3 days
4-5 days
10 days
20-28 days (up to 36)

dronabinol, efavirenz, hemp seed oil

Cocaine (COC)
(parent drug)

Cocaine metabolites
(benzoylecgonine)

 

 

300 1 150 2 (20) 2

 

 

150 1 100 2 (8) 2

6-8 hours (4-12 hr)

 

2-4 days; up to 8 days in heavy use (12-24 hr)

topical anesthetics containing cocaine (e.g., TAC solution)

Methadone (MTD)
during MMT

300 3,4

300 3,4

7-9 days (>24 hr)

Opiates (OPI)
(excluding methadone)

6-acetylmorphine (MAM)
(metabolite of heroin)

Morphine/heroin e (MOR)

Codeine (COD)

2,000 1,2 (40) 2


 

 


10 1,2 (4) 2

2,000 1,2,4 (40) 2

2,000 1,2,4 (40) 2

1-3 days

2-4 hours (1-4 hr)

2-3 days (12-24 hr)

2-3 days (24-36 hr)

fluoroquinolones, ofloxacin, papaverine, poppy seeds, rifampicin/rifampin

Phencyclidine (PCP)

  • Chronic use

25 1,2 (10) 2

25 1,2 (10) 2

7-14 days
Up to 30 days (avg. 14)

dextromethorphan, diphenhydramine, thioridazine

Data assimilated from: Cone 1997; Cone and Preston 1999; Federal Register 2004; Gourlay et al. 2004; Heit and Gourlay 2004; Med Letter 2002; STL 2004; Samyn et al. 1999; Schuckit 2000; Simpson et al. 1997; Strang 1999; Warner 2003; Wolff et al. 1999.

a half-life 2 hours (e.g., midazolam); b half-life 2-6 hours (e.g., triazolam); c half-life 6-24 hours (e.g., temazepam/chlordiazepoxide); d half-life 24 hours (e.g., diazepam/nitrazepam); e heroin is usually detected as its longer-lasting morphine metabolite.

1 Cutoffs in DHHS guidelines for Federal Workplace Drug Testing Programs (urine); last revised November 13, 1998 (63 FR 63483).

2 Cutoffs as proposed by DHHS for urine and oral fluid; Federal Register, 2004 (April 13);69(71):19644-19732. APPROVAL PENDING as of March 2005.

3 Sources: Cone 1997; Cone and Preston 1999. Note: Thresholds may vary by laboratory and/or the assay used.

4 The threshold for some methadone screens is 150 ng/mL, with confirmatory testing cutoffs for methadone and EDDP at 120 ng/mL or less. Confirmatory clinical testing for morphine and codeine in urine is more typically at 300 ng/mL

* General guidelines only – Interpretation of retention times must take into account cutoff values for assay and variability of testing specimens, drug metabolism and half-life, patient physical condition, fluid intake, and route, frequency, and duration of drug administration.

** Detection times noted in oral fluid are via GC-MS or RIA after limited drug dosing and at cutoff levels lower than DHHS guidelines (Samyn et al. 1999).

*** Sources: Med Letter 2002; Warner 2003. Products containing the generic compounds listed are marketed under a variety of brand names. Not all screens or tests share the same cross-reactivity and it is best to check with the particular assay manufacturer.