Determining how a medicine is going to work for an individual patient is very important to medicine safety and efficacy. The way the cannabinoids THC and CBD move through the body (pharmacokinetics) varies depending upon how it is taken. The duration of their action is influenced by close size, dose form, and the route of administration – the lungs, mouth, gut or the skin.
Absorption and distribution
THC and CBD are mainly found in cannabis in their inactive acid form. To activate THC and CBD a carboxyl group must be removed by heat. In practice, this so called ‘decarboxylation’ occurs by heating cannabis flower in a vaporizer, or heating the cannabis flower extracts before being placed into a solution.
The absorption of inhaled cannabinoids results in a maximum (peak) blood concentration within minutes (see figure). Effects in the brain start within seconds to a few minutes, and reach a maximum after 15-30 minutes. They taper off within 2-3 hours.
Absorption is slower when cannabinoids are ingested. Lower, more—delayed peak concentrations occur with oral ingestion. The effects in the brain are delayed for 30-90 minutes, and reach their maximum after 2-3 hours. They last for about 4-12 hours.
Bioavailability describes the proportion of a medicine entering blood circulation after administration. The bioavailability of oral THC and CBD is low. By comparison, the inhalation of cannabinoids has been shown to be more effective and reliable compared to oral administration.
Pharmacokinetics
Pharmacokinetics is abbreviated as PK. It is the study of the movement of medicine within the body. The acronym ADME is used to describe a medicine’s Absorption, its Distribution. Metabolism, and final excretion from our body.
The distribution of cannabinoids in the body are ruled by their lipophilicity (their fat solubility) and binding to blood proteins. THC is distributed widely throughout the body. particularly to fatty tissues. The body storage of THC increases with increasing frequency and duration of use.
Metabolism and elimination The cannabinoids are mainly metabolized by a collection of liver enzymes called cytochrome P450 (CYP450). The same as many other medicines, these enzymes chemically alter the cannabinoids to remove them from our body
(excretion). Besides the liver, other tissues like the heart and lungs are also able to metabolize cannabinoids, albeit to a lesser degree.
