IACM-Bulletin of March 5, 2006

Science — Cannabis and THC effective in the treatment of idiopathic intracranial hypertension

Scientists of the New York State Psychiatric Institute in New York City presented a case report on a woman diagnosed with a longstanding history of idiopathic intracranial hypertension reported improvement of headaches, photosensitivity, transient blindness, enlarged blind spots, and tinnitus after smoking cannabis. All these symptoms and signs, including papilledema (swelling of the optic nerves where they enter the eyes), were associated with increased intracranial pressure. This means that the use of cannabis effectively decreased intracranial pressure. Treatment with THC at a dose of 10 mg twice a day, then reduced to 5 mg twice a day, was also effective.

Idiopathic intracranial hypertension is a neurological disorder characterized by high pressure in the fluid around the brain. It is also known as pseudotumor cerebri because there are some of the signs and symptoms of a brain tumour without a brain tumour being present. The space around the brain is filled with a water-like fluid, the cerebral-spinal fluid (CSF). If there is too much of CSF present the pressure on the brain rises. The cause of the disease is unknown. It is mainly found in overweight women of childbearing age and only rarely in thin men.

(Source: Raby WN, Modica PA, Wolintz RJ, Murtaugh K. Dronabinol reduces signs and symptoms of idiopathic intracranial hypertension: a case report. J Ocul Pharmacol Ther 2006;22(1):68-75)

Science — Detection time of regular THC use in urine shorter than often assumed

According to a review in the current issue of the journal Drug Court Review "it is uncommon for occasional marijuana smokers to test positive for cannabinoids in urine for longer than seven days using standard cutoff concentrations. Following smoking cessation, chronic smokers would not be expected to remain positive for longer than 21 days, even when using the 20 ng/mL cannabinoid cutoff." By using a cut-off of 50 ng/ml in drug screening assays the detection window would typically be not longer than ten days for regular users and between 3-4 days for occasional users.

The author, Dr. Paul Cary of the University of Missouri, noted that it is usually assumed by scientists, the legal system and users of cannabis that the use of cannabis is detectable in the urine by drug screenings 30 days or longer after last consumption. However, he points out that many studies that found a long detection time had major methodical weaknesses. The most serious of these limiting factors would be "the inability to assure marijuana abstinence of the subjects during the studies."

Despite these limitations of the available studies his analysis revealed that very long cannabinoid detection times (30 days or more) are rare. The average detection window for the THC metabolite THC-COOH in urine of regular cannabis users at a cut-off concentration of 20 ng/ml in the studies reviewed by Dr. Cary was 14 days. In many of the studies "only one single subject was the source of the maximum cannabinoid detection time." He concluded that "these rare occurrences have had a disproportional influence" on the perception on the length cannabis use can be detected in urine after last consumption.

The full text is available for free at: http://www.ndci.org/NDCIR%20VI.pdf

(Source: Cary PL. The marijuana detection window: determining the length of time cannabinoids will remain detectable in urine following smoking: a critical review of relevant research and cannabinoid detection guidance for drug courts. Drug Court Rev 2005;5(1):23-58.)

News in brief

Science — Childhood leukaemia

A large case control study did not find an increased risk of childhood leukaemia in children whose mothers had used cannabis during pregnancy. This report from the Children's Cancer Group of the United States and Canada included 517 cases of childhood acute myeloic leukaemia (AML) diagnosed between 1989 and 1993 and 610 controls. Neither ever lifetime use of cannabis by mothers nor cannabis use during pregnancy was associated with an increased risk of childhood leukaemia. Researchers concluded that "the previously reported positive association between maternal marijuana use before or during pregnancy and childhood AML was not confirmed." (Source: Trivers KF, et al. Paediatr Perinat Epidemiol 2006;20(2):110-8)

Science — Hypotension and rimonabant

In this study smoking of a cannabis cigarette had no constant effect on blood pressure but caused symptomatic (dizziness, lightheadedness) hypotension in 7 of 40 healthy subjects. The CB1 receptor antagonist rimonabant attenuated this hypotensive effect suggesting that the CB1 receptor plays a role in mediating this effect. (Source: Gorelick DA, et al. Am Heart J 2006;151(3):754)