Relationship of Blood Alcohol Level to Urine Levels

Since ethanol levels are being determined on random urine samples there is no way to determine the stage of metabolism, i.e. absorption or elimination. For this reason an average conversion factor of 1.3 is used to convert the urine ethanol level to a corresponding blood level (Estimation only).

False Positives:

EIA is optimized to detect ethanol; however other alcohols or volatiles (isopropanol, methanol, acetone, etc.) at high levels may cross-react. Gas Chromatography head space (GC/HS) will specifically identify and quantitate ethanol. In addition a urine sample containing both yeast (contamination or infection) and glucose (diabetes) will result in fermentation within the bladder or sample bottle thus producing ethanol.

AMPHETAMINES

Drug class:
Central Nervous System Stimulant

Retention Time:
Schedule II

Alcohol Equivalencies:
Speed, Crank, Ice, Crystal Meth, Uppers, etc.

Retention: (Detection) Times:
24-96 Hours

NOTES:

1. Thin-layer chromatography (TLC) will specifically identify amphetamine and methamphetamine and rule out over-the-counter and prescription drugs.
   
2. TLC can specifically identify prescription and over-the-counter drugs (as indicated by the underlined drugs in the section above) if requested.
   
3. Albuterol (Ventolin), Alupent and other asthma inhalers will not test positive for amphetamines.
   

BARBITURATES

Drug class:
CNS Depressant

DEA Classification:
Schedule II (Phenobarbital – Schedule IV)

Retention Times:
24-48 Hours (Phenobarbital: 2-3 weeks

NOTES : Notice that barbiturates are detected at different levels both upon screening and confirmation.

Additional Notes:

1. EIA and TLC are specific for barbiturates - No cross-reacting compounds have been found.
   
2. If specific identification of a barbiturate (other than phenobarbital) is absolutely necessary, a GC/MS can be performed

BENZODIAZEPINES

Drug class:
Antidepressants, Sedatives, and Hypnotics

DEA Classification:
Schedule IV
Street Names:
Downs, Nerve Pills, Tranks, etc.

Retention (Detection) Times:
Therapeutic Dose-24-72 Hours; Chronic use over a period of months to
Years can yield retention times of 4-6 weeks.

NOTES :

1. The benzodiazepines which can be detected by TLC are all metabolized in urine to common metabolites, oxazepam and/or nordiazepam, therefore the parent drug cannot be determined. Other chromatography methods, such as GC/MS, upon routine analysis also detect only the benzodiazepines which metabolize to these common metabolites.
   
2. In most cases a specific request must be made to confirm alprazolam, triazolam, lorazepam, clonazepam, flunitrazepam by GC/MS or other chromatographic methods.
   
3. Enzyme immunoassay (EIA) methods detect a broad spectrum of benzodiazepines, however confirmation methods generally detect only limited numbers of benzodiazepines.
   

COCAINE (BENZOYLECGONINE)

Drug class:
CNS Stimulant

DEA Classification:
Schedule II
Street Names:
Coke, Crack, Rock, Snow, etc.

Retention (Detection) Times:
24 – 96 Hours

NOTES :

1. Both the EIA and TLC methods are specific for benzoylgonine. Other drugs such as Lidocaine, Novacain, Benzocaine, etc. do not cross-react to yield false positive results.
   
2. Studies indicate that passive inhalation (second hand smoke) of smoke from crack cocaine does not yield positive results at cutoff levels (0.3 mcg/mL) used for EIA screening.
   
3. It is possible to test positive for cocaine from an individual who has kissed someone who has just snorted cocaine and traces still remain in the nasopharynx area thus cocaine would be present in saliva transferred to the other individual.
   

MARIJUANA (THC)

Drug class:
CNS Depressant, Hallucinogen

DEA Classification:
Schedule I
Street Names:
Grass, Pot, Hashish

Retention (Detection) Times:
: (Based upon a screening cutoff of 50 ng/mL or greater)
Light Smoker 1-3 Days
Moderate Use (~4 times/week) 3-5 Days
Heavy Smoker (daily) 10 Days
Heavy, Chronic use (5+ joints/day) 10-21+ Days
Oral Ingestion 1-5 Days

Elimination Half-Life:
18-24 hours - Essentially one-half of ingested marijuana is eliminated every
18-24 hours regardless of amount ingested. Once smoking is ceased, elimination
occurs at the same rate.

Analytical Note:
EIA screening methods are usually optimized to detect delta-9-THC-COOH, a primary
metabolite of marijuana, but also react with other cannabinoid metabolites therefore
results are expressed in terms of total cannabinoids. Confirmatory chromatographic
methods (TLC, GC/MS, etc.) detect delta-9-THC-COOH only, which constitutes
approximately 30-50% of the total cannabinoid level. Forensic Laboratories reports
semi-quantitative values for THC which represent an estimation only of the true
quantitative total cannabinoid level.

Interpretation of Results :
Urinary concentrations of THC are very difficult to interpret due to variables such as dosage of THC ingested, frequency of prior use, timing of urine collection relative to last exposure to marijuana, rate of release of stored cannabinoids in adipose tissue, and concentration of urine. Therefore the detection of THC metabolites in urine is only an indication of past marijuana uses and is not related to the degree of intoxication or impairment.

METHADONE / METHADONE METABOLITE

Drug class:
Narcotic Analgesic

DEA Classification:
Schedule II

Retention (Detection) Times:
24-72 Hours

NOTES :

1. All EIA negative methadones and/or methadone metabolites are confirmed by TLC.
   
2. Some individuals metabolize methadone at increased rates and may test negative for both methadone and methadone metabolite.
   
3. All positive methadone metabolites from California Methadone Maintenance programs are confirmed by TLC.
   

OPIATES

Drug class:
Narcotic Analgesic

DEA Classification:
Controlled

Retention (Detection) Times:
24-72 Hours

NOTES :

1. If absolutely necessary, information about the possible opiate source may be determined by quantitating codeine and/or morphine by GC/MC.
   
2. 6-monoacetylmorphine may be performed by either TLC or GC/MS to specifically identify heroin as the opiate source.
   
3. Free morphine is reported when the urine is tested without hydrolysis* and total morphine is reported when the urine is hydrolyzed.
   
   * A procedural step during opiate analysis.
   
   

THC INTERPRETATION

The values that Forensic Laboratories report for THC are only to be interpreted as an estimation of the quantitative weight per volume measurement. Urinary THC values are very difficult to interpret due to variables such as frequency of marijuana use, amount used, urine concentration, body weight, etc. Therefore, positive urine specimens for THC merely indicate that marijuana was ingested at some time in the past. Based upon our experience using these values, the urine content of THC can be interpreted as follows:
50-100 ng/ml= Low
100-150 ng/ml= Moderate
Greater than 150 ng/ml= High

The use of these values in determining whether or not the amount of THC detected can be associated with drug effects is very difficult to answer. Because analysis of a single urine specimen cannot distinguish between very recent use and chronic use, the time of use cannot be determined with any certainty. (Blood draw analysis analyzing for unmetabolized THC can be performed for an approximation of THC time of last use.) Therefore these THC units should not be used for ascertaining recent marijuana use based upon a single determination, but for following the progression over time of multiple THC values. Scientific studies have shown that THC is eliminated from the body at a relatively constant rate. The rate is defined in terms of the amount of time it takes for one-half of the drug to be eliminated from the body. The best estimate for this THC half-life is 18-24 hours. This means that half (50%) of the THC taken will be gone after 1 day, 75% will be gone after 2 days, 87.5% will be gone after 3 days, et cetera. Therefore any precipitous increase in THC values following a period of declining values may be an indication of renewed THC use.

NOTES :
The urine THC values offer preliminary interpretation information. Forensic Laboratories strongly recommends consulting a Board Certified Toxicologist for proper interpretation of THC levels prior to any administrative action.

Semi-quantitative EIA Results

The enzyme immunoassay (EIA) values reported by Forensic Laboratories for THC (marijuana) are only to be interpreted as an estimation of the concentration of total cannabinoids (marijuana metabolites) present in a urine specimen. Urinary cannabinoid values are difficult to interpret due to variables such as frequency of use, duration of use, amount used, and an individual's liquid consumption. Therefore, positive EIA results for THC (cannabinoids) indicate use of marijuana but numerous additional considerations, such as THC/Creatinine normalization are required to establish renewed or continued use.

Based on our experience at Forensic Laboratories, the following offers some general guidelines for interpreting laboratory EIA results:

Finally, although an initial EIA positive test in combination with an EIA semi-quantitative positive result provides preliminary interpretation information; clinical consideration and professional judgment should be considered for more reliable interpretation. Forensic Laboratories strongly recommends consulting with a toxicologist and gas chromatography/mass spectrometry (GC/MS) confirmation prior to any administrative or legal action.