Marijuana refers to the dried out leaves, stems, and flowers of the Indian hemp plant, Cannabis sativa, which grows worldwide in temperate and tropical climates. Cannabinoid contains over 400 chemical compounds, including 60 cannabinoids that contain pyran and phenolic rings. The principal psychoactive ingredient in the marijuana plant is ∆9-tetrahydrocannabinol (THC). The THC content of marijuana varies widely ranging from a low of 1% in wild, uncultivated plants to 10 to Liz% in plants grown in specially cultivated varieties.

Medicinal Use and Abuse

The FDA approved the use of synthetic marijuana for the management of anorexia and nausea associated with AIDS in March of 1993. Pharmaceutical products available that contain cannabinoids include dronabinol (Marinol), Sativex, and Nabilone (Cesamet). Abalone, which is available only in Europe and Canada, does not metabolize to THC, and therefore will not produce a GC-MS confirmed positive test). Marijuana has been used therapeutically in the control of acute glaucoma asthma, and the nausea and vomiting that can accompany chemotherapy.

However, the federal government continues to classify marijuana as a Class I substance, and therefore it has no legitimate medical use based on federal law. Twelve states have passed legislation allowing for medical use of marijuana in those states when recommended or prescribed by a physician or health care provider. In most of these states, medical marijuana authorization is permitted for a very wide range of alleged medical conditions and is not restricted to cancer, glaucoma, or AlDS patients. For federally regulated drug testing, the MRO cannot accept medical marijuana use as a legitimate medical explanation for a THC-positive test, even when the donor lives or worlds in a state with a medical marijuana statute. For drug tests conducted under an employers’ own authority in those states that permit the medical use of marijuana, the MRO must rely on the employers’ policy for guidance on how to handle medical marijuana use in verifying a positive TOPIC result.

Marijuana is abused due to its euphoric effects. When self-administered, it is, usually smoked. Clinical effects of marijuana include tachycardia, conjunctival injection, foxy mouth and throat, increased appetite, vasodilatation, broncho-dilation, and decreased respiratory rate. Intoxication results in temporarily impaired concentration, learning, and perceptual motor skills. Paranoia and panic may also be observed in some individuals. Drowsiness frequently follows the euphoric effects. Impairment has been shown to continue for at least 24 h after a dose, long after the euphoric effects have disappeared.

Metabolism and Analytical issues

About 20% of a dose of marijuana is excreted in the urine, mostly within 5 days. The principal urinary metabolite of THC is cpnjugated 11-nor-∆9 tetrahydrocannabinol-9-carboxylic acid (THCCOOH). Numerous additional metabolites, including other carboxylated and hydroxylated metabolites, are excreted in the urine. Tetrahydrocannabinol is extremely lipid soluble. It accumulates in the fat with chronic use and is slowly released over time. The urinary half-life of THCA is about 18 h after a single dose. Using a 50 ng/mL immunoassay cutoff and a GC-MS cutoff of 15 ng/mL, an infrequent user who smokes 1 marijuana cigarette will be positive for up to 3 days after use. Chronic users are likely to test positive in urine for no more than 2 to 3 weeks after last use.

The cannabinoid immunoassays, though calibrated using THCCOOH, cross-react with many urinary metabolites of marijuana. Because of the relatively high cross-reactivity of immunoassays to urinary cannabinoids, the immunoassay cutoff concentration is set higher than the GC-MS confirmation cutoff concentration, which is specific for THCCOOH

Passive inhalation of marijuana smoke, a frequently used defense for marijuana positive drug tests, has been studied extensively. Although passive inhalation of marijuana smoke does occur, unrealistic exposure conditions would be required to produce a positive result. It is generally agreed that passive exposure is not a valid explanation for a positive test result and federal regulations direct MROs to reject claims of passive inhalation as a cause of positive marijuana drug tests at or above the DOT cutoff levels. Some donors may raise the issue that they unknowingly ingested marijuana in beverages and/or foods. There is no evidence that beverage “spiked” with marijuana will yield a positive THE test when ingested. Marijuana cooked or baked en foods can produce THC-positive test results, however the amount of orally ingested marijuana necessary to produce a positive drug test is generally discernible by increased fibrous texture and taste, and thus is rarely “unknowingly or unintentionally” consumed. Again, for federally mandated testing, the MRO is prohibited from accepting food/beverage ingestion, even if documented, as a legitimate medical explanation for a THC-positive test.

The usage of hemp-containing products is also sometimes claimed as an explanation for a positive test. Research has shown that commercially available hemp seed and hemp flour food products do not contain enough THC to produce a positive test. Hemp oil, particularly varieties sold in Europe, does contain enough THC to produce a positive test if used regularly in dietary applications. Hemp products used as personal care products (Eg, shampoos and lotions) do not contain sufficient THC to produce a positive test. Again, for federal drug testing the hemp product explanation is not recognized as a legitimate medical explanation for the positive test.

Thus, only a current prescription for either Marinol or Sativex can be accepted by the MRO as a medical explanation for a THC-positive test. Since all DOT donors are considered to be performing work with a direct impact on public safety, DOT requires MROs who in their Reasonable medical judgment” believe that a donor may be Likely” to present a Significant safety risk” or may be medically unqualified under a DOT agency rule to report this to the employer. MROs should consider whether verified prescriptions for Marinol or Sativex would place donors into this category.

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