Pharmacokinetics
What is pharmacokinetics?
Pharmacokinetics is the study of how the body affects a drug or specific substance once the drug has been administered. It is a branch of pharmacology, and its meaning can be derived from the Ancient Greek ‘pharmakon’ for “drug” and ‘kinetikos’ for “putting in motion” or “moving”.
What are the pharmacokinetics of medicinal cannabis?
The pharmacokinetics of medicinal cannabis will be impacted by various influencing factors including how the medicinal cannabis is administered, the composition of the medicinal cannabis - for example what ratio of cannabinoids it contains - as well as the patient-to-patient variability of age, height, metabolism and other individual factors.
Pharmacokinetics of THC vs CBD
As the method of administration plays a role in the pharmacokinetics of medicinal cannabis, it is logical to assess the pharmacokinetics of its two most major cannabinoids, Tetrahydrocannabinol (THC) and Cannabidiol (CBD), through the most common methods of usage: inhalation, oral ingestion and sublingual ingestion.
Inhalation
Inhalation offers swift absorption, with both THC and CBD being delivered to the central nervous system via the lungs, by-passing metabolism by the liver, and allowing the active ingredients to enter the central nervous system more quickly and in a higher dosage concentration. Whether or not a patient is suited to rapid absorption will depend on their condition.
Oral ingestion
Oral ingestion results in THC being metabolised by the liver extensively, which causes a slower onset of action. When ingested orally, THC has lower bioavailability when compared to the inhalation pathway. Determining the most suitable format for a patient is at the sole discretion of a medical practitioner who should use their own clinical judgement in relation to the individual patient circumstance.
While oral ingestion has a slower onset of action, in general it has a longer duration of effect. Additionally, when medicinal cannabis containing THC is ingested, THC is converted into 11-OH-THC, which is another psychoactive metabolite, which may be potentially more psychoactive than THC.
Following oral absorption, CBD is distributed in the brain, adipose tissue and other organs, with the distribution influenced by its high lipid solubility.
Sublingual ingestion
Sublingual ingestion means placing the medicinal cannabis under your tongue and allowing its active ingredients to be absorbed into a patient’s bloodstream this way. This method partially bypasses the digestive system (compared to ingesting medicinal cannabis orally) and allows both the THC and CBD to be absorbed more quickly.
The four stages of pharmacokinetics
Once the medicinal cannabis has been administered, there are four stages of pharmacokinetics:
Absorption
Absorption refers to the stage of pharmacokinetics after ingestion, when a drug or specific substance travels from the site of administration into the body’s circulation. Medicinal cannabis is absorbed, either through the bloodstream or through the digestive system. In the instance of medicinal cannabis products such as lotions, oils or creams, there can be local absorption through the skin.
Distribution
Once medicinal cannabis has been absorbed, the next stage in the pharmacokinetic process is distribution, when cannabinoids are distributed throughout the body, including to the brain. Liver and fatty tissues. Here, they bind to cannabinoid receptors in the endocannabinoid system.
Metabolism
Metabolism of medicinal cannabis occurs predominantly in the liver. Depending on the method of ingestion, some forms of medicinal cannabis, such as products that are orally ingested, are subject to extensive first-pass liver metabolism, meaning they are metabolised before being released into the bloodstream.
Others, such as inhalation, are able to bypass this first-pass metabolism by the liver and enter the bloodstream directly to be delivered to the central nervous system more quickly.
Elimination
The elimination stage of pharmacokinetics occurs mainly through faeces and urine. The elimination will depend on the product’s half-life, which is determined by the specific cannabinoid profile, the strength of the actives it contains and the method by which it has been administered.
How long medicinal cannabis stays in a patient’s system may have legal ramifications for whether or not they are able to operate heavy machinery, attend their place of work or drive.
What is pharmacodynamics?
Pharmacodynamics is another branch of pharmacology, which, by contrast, refers to how a drug or specific substance affects the organism once it has been administered, rather than studying how the substance is impacted by the organism, as is the case in pharmacokinetics.
What is the pharmacodynamics of medicinal cannabis?
As with pharmacokinetics, the pharmacodynamics of medicinal cannabis are determined by the ratio and amounts of major and minor cannabinoids that the medicinal cannabis contains. Typically, the pharmacodynamics of medicinal cannabis involve key cannabinoids, such as THC and CBD, interacting with the body’s endocannabinoid system and THC binding to its CB1 and CB2 receptors.
Pharmacokinetics vs pharmacodynamics
To some extent, pharmacokinetics and pharmacodynamics both refer to the same process or interaction, but each is taken from a different viewpoint.
Pharmacokinetics looks at the interaction between a drug and an organism from the perspective of the drug, and the impact that the organism has on it. In other words, the drug’s movement through the body.
Pharmacodynamics refers to the interaction between an organism and a drug, assessing the effect that the drug has on the body. In other words, the drug’s actions within the body.
Both are branches of pharmacology, and are crucial for understanding drug efficacy, safety and dosage regimens.
Healthcare professionals can find out more useful information about medicinal cannabis and its administration by accessing the healthcare professionals portal. If you have any questions about our products, contact us today.
