- Cannabis Cream
One therapeutic principle is to apply a medication as close to the source of the problem as possible. One example is if somebody has a skin lesion, an antibiotic skin cream is preferable to an oral dose. Oral doses are more appropriate for gastro-intestinal conditions as they coat the G.I. tract. Inhaled cannabis is preferred for immediate relief from acute conditions. Appropriate application methods attempt to maximize desired effects and minimize undesired side effects. For medical users the psychoactive effects are sometimes undesired as they may conflict with their daily activities. Patients find they can reduce the amount of cannabis inhaled or ingested by applying an oil externally, directly to the site of concern. This has the benefit of reducing the amount of cannabis delivered to the brain through the bloodstream, reducing the psychoactive effects.
Studies measuring the nanogram per millilitre of THC in the bloodstream have shown that anywhere in the range of 7-29ng/mL is enough to produce the subjective “high” effect. (source) A study on trans-dermal cannabinoid delivery found that after an hour and a half exposure blood plasma levels reached only 4.4ng/mL. Permeation of cannabidiol (CBD) and cannabinol (CBN) was found to be 10-fold higher than for Δ8-THC. (source) The consumption of a chocolate cookie containing 20 mg THC resulted in peak plasma THC concentrations ranging from 4.4 to 11 ng/mL, (source) barely passing into the psychoactive range. Studies on very weak cannabis (1.6% THC) when smoked resulted in mean peak THC blood plasma levels of 77 ng/mL, approximately 10 times that of eating a cookie, and 20 times the topical administration.