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 anti-biotic 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.
Health Canada’s information for health care professionals contains some of the few studies on topical application. 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, (source) approximately 10 times that of eating a cookie, and 20 times the topical administration.
(The red line Indicates the level of THC needed to produce the ‘subjective “high” effect)
While topical cannabis only minimally passes through the skin into the bloodstream, this doesn’t mean it’s ineffective. Cannabinoids bind to CB1 and CB2 receptor sites in our bodies, which have been located in nerve fibres of the skin, skin cells (keratinocytes), cells of the hair follicles, sweat glands, and other cells present in the skin. “Abundant distribution of cannabinoid receptors on skin nerve fibers and mast cells provides implications for an anti-inflammatory, anti-nociceptive action of cannabinoid receptor agonists.” “It seems that the main physiological function of the cutaneous ECS is to constitutively control the proper and well-balanced proliferation, differentiation and survival, as well as immune competence and/or tolerance, of skin cells.”
At the V-CBC where topical “massage” oils have long been available to members, the combination of a topical product with some form of internal administration is reported to produce greater pain relief than either on its own. Topical application reduces pain where it arises, while internal routes increase the brain’s resistance to incoming pain signals. Arthritis sufferers are the most common topical cannabis users, although members have reported rapidly healing third degree burns, experienced relief from eczema, psoriasis, atopic dermatitis and in one case cleared a poison oak rash.
The fat soluble cannabinoids, soaked in vegetable oil and strained of the plant bulk (How to), create a simple and effective lotion.
- Cannabis infused olive oil
- Vitamin E (to help with absorption)