Like other medicines, medicinal cannabis is available in different dose forms (e.g., inhalation, oral, transdermal) to meet different patient requirements. How medicinal cannabis is administered or taken depends on its close form.
The dose form is really important. It can influence patient behaviour in different ways, including if patients actually take their medicine and adhere to their daily regimen
Inhalation-by the lung
Dose form
Using a vaporizer or inhalation medical device. Cannabinoids are inhaled (from cannabis flower) as a vapour which then enter the bloodstream from the lungs.
Inhalation has proven to be an efficient administration route. The inhaled vapour is quickly absorbed by the lungs. The immediate onset of action means it is the preferred choice for many patients. The vapour contains cannabinoids and terpenes in consistent. measurable quantities. The speed of onset simplifies titration — the ability to achieve the correct dose without side effects – and achieve fast relief from symptoms. The amount of cannabinoids delivered depends on the depth of inhalation and breath hold. While inhalation results in higher blood levels of cannabinoids, their effects compared to oral administration is shorter in duration.
Medical vaporizer
Given the risks from smoking, patients nowadays seek reliable, affordable and portable vaporizers or inhalation devices. Research dedicated to advancing vaporizer and inhalation technology has seen major developments in device quality.
Medical vaporizers for the administration of cannabis flower – instantly we think of e~cigarettes or vape-pens – are in fact quite different. The vapour does not contain nicotine, liquid propylene glycol, glycerol nor synthetic flavours. There is also no large, socially intrusive, toxic vapour cloud. These vaporizers (or inhalation devices) offer patients an effective, safe, and easy to use delivery system.
Smoking
Ultimately, smoking medicinal cannabis is harmful to patients’ health and is therefore not recommended.
Toxic pyrolytic compounds are produced when the plant material is smoked (i.e. combustion). Typically cannabis flower is rolled into a ‘joint’ cigarette, and cannabinoids are inhaled as smoke into the lungs. The medicine enters into the bloodstream from the lungs. Smoking cannabis results a rapid onset of action. The effect is noticed within minutes. While smoking results in higher blood levels of cannabinoids, their effects compared to oral administration is shorter in duration. Furthermore, unless it is fully standardized, the amount of THC and CBD in cannabis flower can vary greatly between batches. The amount of THC delivered also depends on the depth of inhalation, puff volume and duration, and breath hold.
Pharmaceutical quality cannabis flower for vaporization to deliver consistent therapeutic levels of cannabinoids, the product must be of pharmaceutical quality. This cannabis flower is genetically and chemically standardized according to pharmaceutical standards. From a patient safety perspective, it is free of microbial contaminants, pesticides, impurities and heavy metals. These are qualities that make the vapour safer for inhalation into the lungs.
Oral- by the mouth
Dose form Cannabinoids (whole plant extracts or individual cannabinoids) taken by mouth and either swallow/(xi (oral), or absorbed from under the tongue (sublingual). When swallowed, the medicine enters into the bloodstream via the stomach. intestines and the liver. When absorbed from under the tongue, the medicine bypasses the liver and enters into the bloodstream directly.
Oral preparations are familiar dose forms. They are similar to other medicines patients already take, and are easy to administer. As a result, concentrated cannabis extracts are becoming increasingly popular.
Oils
An increasing number of patients are using extracts of cannabis flower. Whole plant cannabis extracts contain cannabinoids and terpenes in a concentrated dose form. Often they are called ‘oil’ because of their dark viscous appearance. The extract is dissolved in an oil (e.g., olive, sunflower, peanut) to act as a carrier and ease administration.
A single dose can be dispensed from a dropper and placed under the tongue. It is absorbed from the lining of the mouth (termed sublingual absorption) where upon it enters the bloodstream.
Sublingual delivery increases total available dose. This means smaller doses are required for the same effect. compared to swallowing capsules or drinking tea.
Sublingual dose forms can provide a reliable uniform dose.
Sprays
Sprays are also administered under the tongue just as oils. An example is Sativex, a standardized (oromucosal) form of a pharmaceutical product, made from two strains of cannabis. One strain produces mainly THC and the other mainly CBD. Exacting proportions of the active compounds THC and CBD are dissolved in an alcohol solution. This is placed in a metered-dose bottle which is sprayed under the tongue.
Capsules
An alternative oral dose form are capsules. These typically contain exacting concentrations of single cannabinoids (i.e. THC and CBD) dissolved in a carrier oil. The capsule is swallowed, breaks open, the drug is released and finally absorbed in the stomach and intestines. The rate (time) of absorption can be unpredictable, and varies depending on, for example, if food is present, and if the patient is mobile (able to exercise/walk freely). Interestingly, THC itself slows the rate of gastric emptying (from the stomach to intestine). Oral administration (by swallowing) results in slower onset of action, lower total blood concentration, and a longer duration of effects compared to inhalation. Total cannabinoid content is affected by liver metabolism and stomach contents. This means oral dosing can be less unreliable and unpredictable.
Tea or infusion
A proportion of patients consume medicinal cannabis as a tea (cannabis flower infused in hot water). Teas are swallowed and the cannabinoids are absorbed in the stomach and small intestine. Similar to oral dosing, the total cannabinoid content is affected by liver metabolism and stomach contents. This means dosing by tea may be unreliable and unpredictable.
Furthermore, tea typically has a low concentration of cannabinoids, the tea composition is effected by boiling time, volume of tea prepared, and the length of time in storage. This means dosing by tea can provide a less certain therapeutic effect.
Edibles
Other whole plant dose forms include edibles such as cookies/brownies. It is difficult to obtain a consistent cannabinoid composition in edibles. Patients can easily overdose, particularly as the time to effect may be 2-3 hours and patients may ingest a second dose if they are awaiting effects.
The therapeutic effect is less certain than standardized oral products and it usually takes longer to achieve. As a result, edibles are not considered a therapeutic product.
Transdermal- by the skin
Dose form
Transdermal literally means across the skin. The typical dose forms include creams which are applied to the skin surface or a mucous membrane; and, transdermal patches which are a medicated adhesive patch applied directly on the skin. A specific dose is then administered gradually over a set time.
Transdermal dose forms are being investigated for their clinical use and application. Currently they are being used to treat certain skin conditions and for localized muscular or joint pain.
Given that most cannabinoids dislike water (are highly hydrophobic), it can be difficult to achieve a reliable dose form that is applied to the skin and can achieve appropriate blood concentrations. However, novel nanotechnology may overcome this. Dose forms such as creams are intended for local application and action. These do not require achieving penetration through the skin into the blood stream.
