Routes of Administration

In general, cannabinoid medicine can be inhaled or administered orally. The pharmacokinetic properties differ depending on the route of administration. Which routes may be preferred in each individual case depends on the judgement of the physician, among other factors. In certain cases a combined oral and inhalative administration schedule may be reasonable.

In general, cannabis can be inhaled or administered orally. Moreover, the uptake of cannabinoids in appropriate preparations is also possible via the oral, nasal, gastrointestinal or vaginal mucosa and due to its fat-soluble properties also via the skin (e.g. in cosmetics or ointments). 

However, to our knowledge reliable pharmacokinetic data is only available for oral and inhalative administration so far.

For inhalation usually whole, dried cannabis flowers are used. The cannabinoids in the flowers are present in their acidic form and are decarboxylated by heat during smoking / vaporizing and are thereby converted into their pharmacologically more effective neutral forms. The neutral forms are already present in extracts; decarboxylation of cannabinoid acids already occurs during the extraction procedure. The inhalation of cannabinoids together with combustion byproducts (e.g. as joint, possibly combined with tobacco) is not recommended for medical application by the German Federal Ministry for Drugs and Medical Devices (Bundesministerium für Arzneimittel und Medizinprodukte, BfArM) due to potential associated health hazards as well as a higher risk of abuse.

During inhalation, the effect sets in within several seconds to minutes; the maximum drug concentration in the blood serum can reach values of up to 300 nanograms per ml on a short-term (several minutes) with noticeable effects lasting for 2-3 hours. During oral intake the effect sets in within 30-90 minutes; the maximum drug concentration in the blood serum only reaches values of up to 15 nanograms per ml. However, the concentration remains stable for several hours on this level and the noticeable effect lasts for up to 8 hours (see Fig. 1).

Fig. 1 Time course of the subjective effect after oral and inhaled administration. The subjects rated the level of intoxication on a scale of 0-10 (adapted from Cannabis: Verordnungshilfe für Ärzte)

Which route of administration is more beneficial depends on the judgement of the physician, the patients´ request, the indication and if necessary by taking into account an accompanying illness. In certain cases a combined oral and inhalative administration schedule may be reasonable. 

https://www.bfarm.de/DE/Bundesopiumstelle/Cannabis/Hinweise_Aerzte/_node.html

Cannabis: Verordnungshilfe für Ärzte von Franjo Grotenhermen; Klaus Häußermann – ISBN 10: 3804737595 – ISBN 13: 9783804737594