Formulation of cannabinoids and cannabis extracts as microparticles for improved stability and bioavailability

Motivation: In recent years there have been a large increase of interest in the use of cannabinoids in medical treatment, since they have been shown to have effects in areas such as cancer treatment, Chemotherapy induced emesis, inflammation, pain relief, Spasticity, anxiety and glaucoma. However, the 2017 report from NASEM (National Academies of Sciences, Engineering and Medicine) reviewed all of the published cannabinoid clinical evidence for medical use and stated that effects of cannabis are understudied, and research findings are mixed. It concluded that the underdeveloped evidence base poses a public health risk and rightly addressed complexities of cannabis research that need to be resolved. During the last couple of years there has been a huge development in the area of producing medical-grade cannabis. This development fosters the need to increase the research and development of new cannabinoid formulations and to investigate the physico-chemical properties and interactions of cannabinoids in new lipid and excipient formulations.
State of the Art: One of the unique methods of the PhyLife group at SDU, comprise a series of micropipette manipulation techniques associated with the study of microscopic interfaces and single microparticles. During Dr. Utofts PhD-study at SDU he used and mastered these micromanipulation techniques, including measurements of interfacial tension, microdroplet dissolution into an immiscible second solvent, and microcrystal precipitation and characterization. This technique has already shown great utility in fundamental studies of gas and liquid dissolution, and the formation of drug, polymer, and protein microparticles. He mainly focused on water-in-oil systems where the aqueous phase contained salts or proteins and the surrounding oil phase could dissolve the water and so concentrate the aqueous solution into a micro-crystallized salt or dehydrated microglassified protein bead. Using the Epstein Plesset model, modifying it, and fitting it to the data of individual dissolving microdroplets, these studies allowed me to characterize fundamental physico-chemical properties of multiphase, multicomponent systems including salt micro-crystallization, antibody-protein microglassification, and the interfacial tension and water-ethanol solubility of a test hydrophobic material (triolein). He now looks to apply his current skills and expand them by working with new medicinal cannabinoid formulations in collaboration with international and industrial partners in the Netherlands by using micromanipulation and microfluidics to test and produce new formulation methods of cannabinoids.
Current Knowledge: Smoking, intravenous, transdermal, sublingual and buccal routes appear to be the most efficient modes of administration, owing to variable absorption and high first-pass metabolism with oral modes of administration. However, even bioavailability following the smoking route is extremely variable due to parameters such as number of inhalations, duration, inhalation spacing, and breath hold. Compared with intravenous administration, lower THC maximum plasma concentration is achieved after smoking which again achieves a significantly higher concentration compared with oral ingestion. This has inspired the development of both lipid nanoparticles and PLGA nanoparticles as an oral delivery platform for cannabinoids. Cannabinoids, being lipophilic materials with a low water solubility have the potential of being formulated as nano- and microparticles. Previous formulations have included the use of sesame oil (which contains a high degree of long-chain triglycerides)
to increase the absorption and systemic exposure of the cannabinoid. Dr. Utoft have previously been involved in a thorough characterization of triolein physico-chemical properties and its formulation into nano- and microparticles as well as in investigations into solvent dissolution and precipitation effects in micro systems.
Purpose: To develop stable formulations of natural cannabinoid extracts in the form of nano- and/or microparticles. The collaboration partner, Stabican, was founded as a pharmaceutically organized Medicinal Cannabis company, with the vision to formulate natural cannabinoids from extracts as a stable, processable and quality validated (QA) drug substance. On the long run, several formulations based on this first development will be targeted, like tunable cannabinoid profiles or controlled release lipid/polymer microspheres. The current problems with natural cannabinoid extracts are:
• Stability, especially THC (Δ9-tetrahydrocannabinol, in vast majority present in cannabis as THCA).
• Dosage of the cannabinoids, as total and as the individual composition of all known natural cannabinoids (more than 100 known).
• Reproducibility of the physical and chemical properties of the formulations.

• Initial idea was to use numbers from previous PLGA/protein microparticle batches that used injection of 40 µl (50 mg/ml) solutions into 1 ml solvent.
• With a DCM density of 1.33 mg/ml, the 40 µl is equal to 53.2 mg of DCM.
• DCM solubility in water is only 20 mg/ml @ 20 °C.
• So, to even solubilize 40 µl (53.2 mg), almost 3 ml water was needed.
• This automatically eliminated the idea of using higher volumes of THC solution.
• This did however introduce the problem of the f value (saturation level of DCM in water) after having dissolved the DCM during homogenization.
• Usually we would want to keep the final f-value below 0.1 to assure complete solvent removal, but for 40 µl that would require 26.6 ml of water, which would give too low a particle concentration (and it is also too large a volume for the T10 basic ultra-turrax, to handle).
• An upside to DCM in this case was its high vapor pressure, which meant it evaporated easily, thus lowering the f-value in the water over time.
• Particle formation happened with the T 10 basic ULTRA-TURRAX @ speed 4 of 6 for 5 minutes.
• With a benzyl alcohol density of 1.04 mg/ml, the 40 µl is here equal to 41.6 mg of benzyl alcohol.
• Benzyl alcohol solubility in water is 40 mg/ml @ 20-25 °C.
• So we had less volume and higher solubility as compared to DCM experiments, which was good. To solubilize 40 µl (41.6 mg), we needed a little more than 1 ml water.
• On the other hand, benzyl alcohols boiling point is 205 °C, which gives it a very low vapor pressure at room temperature.
• This resulted in the water evaporating much faster than the benzyl alcohol, which again makes the water droplet experiments under the microscope quite problematic.
• Benzyl alcohol just precipitates back out of solution as water evaporates, which interferes with the formed particles.
• The benzyl alcohol in water batches produce an incredible amount of stabilized air bubbles over time, which interfered with the experiments/observations.
• Pure water droplet evaporation was done to compare, and this system did not have nearly as many air bubbles.
• Small scale batch preparation of the THC : cetyl alcohol : cetyl palmitate, microparticles from DCM have been carried out.
• Minimum homogenization speed was found to be 4 (14000 rpm).
• Particles in the 1-20 µm range was produced as a white-ish residue after water evaporation.
• Small scale batch preparation of the THC : cetyl alcohol : cetyl palmitate, from benzyl alcohol have been carried out.
• Optimization of this system is needed for further experiments to give additional information.