Most commonly, the flower of the plant is dried, ground, and smoked. The main benefit of smoking is that it provides rapid relief on the timescale of minutes. Furthermore, this instant feedback allows users to adjust their dosing to either increase or maintain a steady state of relief. This control also reduces the risk of experiencing adverse effects due to overconsumption, such as dizziness, paranoia, or anxiety. Similarly, vaporization also provides rapid onset of effects, with the added benefit of being considered a much safer and more efficient means of cannabis consumption compared to smoking. Pyrolysis of cannabis has been shown to generate more than 2000 new compounds, including hazardous components such as carbon monoxide and polycyclic aromatic hydrocarbons. In addition, some studies have shown that 30-50% of THC is lost during burning. Since vaporization involves heating dried cannabis to temperatures below combustion, the production of smoke is avoided, and fewer harmful combustion by-products are created. Thus, vaporization is a very efficient method of consumption that allows for rapid relief of symptoms and is overall a superior and healthier means of consuming cannabis compared to smoking.
Oral administration through either ingestion or sublingual absorption are also popular methods of cannabis consumption. Like vaporization, oral consumption avoids exposure to smoke and other hazardous pyrolysis by-products. However, cannabis must be decarboxylated prior to ingestion. Oral administration often involves the consumption of a cannabis extract rather than the actual plant material. For oral sprays, such as Sativex, the extract is often mixed with a diluting/carrier agent, such as propylene glycol. Alcohol, flavouring, and sweeteners may also be added to adjust the viscosity and taste. Application of the product under the tongue results in rapid absorption due to the high vascularity of the sublingual region. However, taste is obviously a concern with such products, and a titrated spray dispenser is required for consistent dosing. Alternatively, an infusion can be made by soaking decarboxylated cannabis in butter or edible oil. This infusion can be used for cooking or baking applications. However, making this infusion is a time-consuming and highly tedious process that, if completed at home, will produce extracts with unknown and highly variable THC concentrations. Because of this dosing challenge, capsules may be a safer and more convenient method of cannabis administration, resulting in higher patient compliance and a lower risk of experiencing adverse effects.
Despite being a popular historical method of consuming cannabis, tea preparations are not popular or recommended for several reasons. First, cannabinoid extraction during steeping will be extremely low due to the low water solubility of cannabinoids. However, the addition of cream or non-skimmed milk may aid in this. Secondly, water temperatures may not be sufficient to completely decarboxylate cannabinoids. Thirdly, the final concentration of cannabinoids in the tea will be unknown (and low), making tea a very inefficient way of consuming cannabis. Compared to sublingual administration or inhalation, there is a noticeable delay in the onset of therapeutic action following ingestion. For this reason, ingestion may not be a preferred means of consumption if instant relief is desired.
While inhalation and oral administration are the most common (and therefore the most studied) methods of cannabis consumption, rectal, transdermal, and ophthalmological administration are also possible. All these methods are commonly used for drugs that are not suitable for oral administration, often due to their potential to irritate the stomach or gastrointestinal tract, and more commonly due to their low oral bioavailability. For cannabis, these methods also avoid the generation and consumption of smoke and other hazardous combustion by-products.
Transdermal application may be achieved by incorporating decarboxylated cannabis oil into topical products, such as lotions, gels, or transdermal patches. Such products may be most useful for individuals seeking to treat localized, physical pain. Ophthalmological and suppository products are less common, but animal studies have demonstrated their potential as alternative methods of cannabis consumption offering rapid absorption.