Nanoemulsions and Water-Soluble Cannabinoids

The oil-in-water problem that keeps formulators up at night

Around 60–70% of new drug candidates are poorly water-soluble. Cannabinoids sit squarely in that cohort. They are lipophilic , they dissolve readily in fats and oils, not in the watery environment of the gut. If you've ever read about bioavailability in the context of cannabinoids, this is the underlying issue: oral absorption of compounds like cannabidiol from a standard oil-based preparation is genuinely low, highly variable between individuals, and strongly influenced by whether you've eaten a fatty meal. That's not a flaw in any particular product; it's basic physical chemistry.

Nanoemulsion technology is one of the more serious attempts to work around this constraint. Understanding what it is , and what it genuinely achieves versus what's overclaimed , requires a quick grounding in emulsion science. Bear with me, because this is actually interesting.

What is a nanoemulsion, exactly?

An emulsion is a mixture of two immiscible liquids, typically oil and water, stabilised by a surfactant (an emulsifying agent). Conventional emulsions; think salad dressing, have droplet sizes in the micrometre range, from about 1 to 100 micrometres. They're often cloudy or opaque and tend to separate over time. A nanoemulsion reduces those droplet sizes dramatically, typically to between 10 and 200 nanometres. At that scale, the droplets are small enough that the preparation becomes optically clear or only slightly hazy, and stability improves considerably.

The droplets in a cannabinoid nanoemulsion are essentially tiny oil globules, each one containing dissolved cannabinoid molecules; suspended throughout an aqueous medium. The surfactant layer around each droplet makes that suspension stable. The goal is that when this preparation reaches the gastrointestinal tract, the cannabinoid is presented to the absorptive surface of the gut in a form that doesn't require the body to first emulsify an oil bolus before absorption can begin.

A closely related formulation type is a self-emulsifying drug delivery system (SEDDS), which is a lipid-based mixture that spontaneously forms an emulsion upon dilution with gastrointestinal fluids. These are often discussed alongside nanoemulsions in the pharmaceutical literature. The mechanisms differ slightly, but the end objective is similar: reduce the particle size of the oil phase to enhance contact with gut epithelium.

Why does particle size matter for absorption?

The gastrointestinal mucosa, the lining of the small intestine in particular, absorbs lipophilic compounds partly through passive diffusion and partly via specialised lymphatic pathways involving structures called lacteals. Reducing droplet size to the nanometre range does several things that are relevant here.

First, it dramatically increases surface area. Surface area scales inversely with droplet radius, so reducing a 10-micrometre droplet to 100 nanometres increases surface area by a factor of roughly 100. More surface area means more cannabinoid molecules are simultaneously available at the aqueous-lipid interface where absorption occurs. Second, small droplets have different colloidal behaviour; they're less prone to gravitational separation and more likely to remain homogenously dispersed as the preparation moves through the gut. Third, some research indicates that very small lipid droplets may interact differently with the bile salt/mixed micelle system that the gut normally uses to handle dietary fats; potentially accelerating the absorption process.

The upshot in pharmacokinetic terms is that nanoemulsions of lipophilic compounds have, in a number of laboratory and clinical studies, demonstrated faster onset of measurable blood concentrations and, in some formulations, higher peak concentrations compared with conventional oily preparations. A 2019 review in the European Journal of Pharmaceutics and Biopharmaceutics surveyed the published data on lipid-based drug delivery systems for cannabinoids and found consistent evidence of improved in-vitro dissolution and, more variably, improved in-vivo absorption, though the authors were careful to note that the field still lacks large, standardised comparative trials. That caveat matters.

The role of surfactants and co-solvents

Producing a stable nanoemulsion at pharmaceutical grade isn't trivial. Surfactant selection is everything. Common pharmaceutical surfactants include polysorbates, polyoxylglycerides, and various lecithin-derived phospholipids. The concentration and HLB value (hydrophile-lipophile balance) of the surfactant determines whether the system is an oil-in-water emulsion (cannabinoid-in-water, the configuration relevant to aqueous products) or a water-in-oil emulsion.

Co-solvents, typically short-chain alcohols or polyols like propylene glycol or glycerol; are often added to reduce the interfacial tension further and improve the spontaneous emulsification process. Each of these excipients has its own safety and regulatory profile, and in an Australian context, any formulation intended for human therapeutic use must comply with the Good Manufacturing Practice standards specified under the Therapeutic Goods Act 1989, as administered by the TGA. The allowable excipient list for oral and sublingual products is not unlimited.

Aqueous solubility versus true "water-soluble" cannabinoids

Honestly, I find the phrase "water-soluble cannabinoids" a bit misleading, and I'd argue it's used loosely in a lot of educational material. Cannabinoid molecules themselves, THC, CBD, CBG and their relatives, are not chemically water-soluble in the way that, say, table salt is. What nanoemulsification achieves is the dispersal of those oil-soluble molecules into a stable aqueous phase. The molecules remain in their lipid environment inside each nanodroplet; the system as a whole is water-dispersible. That's a meaningful distinction if you're trying to understand what's actually happening, rather than just the marketing shorthand.

There is a separate and more genuinely chemical approach: cyclodextrin complexation, where the hydrophobic cannabinoid molecule is enclosed within a cyclodextrin ring structure, making the complex genuinely water-soluble at the molecular level. This is a different technology and it appears in pharmaceutical research literature separately from nanoemulsions, though both are sometimes grouped under the "water-soluble cannabinoids" banner.

Implications for pharmacokinetics and formulation design

From a pharmacokinetics perspective, the practical significance of nanoemulsion approaches is primarily about reducing variability. The so-called "food effect"; where absorption of a fat-soluble compound is highly dependent on co-ingestion of dietary fat, is one of the major sources of unpredictability with conventional cannabinoid preparations. Nanoemulsions partly internalise the lipid phase, meaning the formulation carries its own emulsification system rather than relying on what the patient has or hasn't eaten. Whether this translates to clinically meaningful improvements in consistency of effect depends heavily on the specific formulation and the cannabinoid involved; the published data vary.

First-pass metabolism in the liver remains a factor regardless of formulation approach. Cannabinoids absorbed via the gut wall enter portal circulation and reach the liver before systemic distribution. No emulsion technology changes that pathway. What it may change is how much cannabinoid actually arrives at the gut wall in an absorbable form in the first place.

Sublingual and buccal nanoemulsion formulations take a partly different approach, aiming for some absorption directly through oral mucosa and thereby bypassing first-pass metabolism to a degree. The mucoadhesive properties of the formulation matter here, and this is an active area of pharmaceutical research.

Regulatory considerations in Australia

Any cannabinoid product intended for human therapeutic use in Australia sits within a defined regulatory framework. Cannabinoid medicines containing THC are Schedule 8 controlled drugs under the Poisons Standard. CBD preparations above certain thresholds are Schedule 4 prescription-only medicines. Access pathways include the TGA's Special Access Scheme and the Authorised Prescriber pathway.

The formulation technology; nanoemulsion, conventional oil, capsule, or any other, doesn't change those scheduling classifications. A nanoemulsion of a Schedule 8 cannabinoid is still a Schedule 8 controlled drug. Any product carrying therapeutic claims in Australia must either be listed or registered on the Australian Register of Therapeutic Goods (ARTG) or supplied under a TGA access pathway. The sophistication of the delivery system doesn't affect that requirement.

I spent a couple of hours last winter at the Greenslopes branch of the State Library digging through the TGA's published guidance on lipid-based drug delivery systems, partly for this piece, partly because I'd gone in there to look for something else entirely and got thoroughly sidetracked, which is my characteristic hazard. The TGA's published guidelines on pharmaceutical development (aligned with ICH Q8 guidance) do address nanoemulsions and SEDDS formulations in the context of quality requirements, which is worth knowing if you're trying to understand how these products move through the approval process.

What the research landscape actually looks like

The in-vitro evidence for nanoemulsion-enhanced cannabinoid dissolution is fairly consistent. The in-vivo pharmacokinetic evidence is more mixed, partly because the field lacks standardised methodology. A 2020 paper published in Pharmaceutics (MDPI) directly compared several lipid-based formulations of CBD in a rat model and found significant differences between formulations in Cmax (peak blood concentration) and AUC (area under the curve; a proxy for total exposure), but noted that translation to human pharmacokinetics requires caution given interspecies differences in gut physiology and bile composition.

Human pharmacokinetic studies for nanoemulsified cannabinoids exist but are limited in number and sample size. The short version is: the technology has a sound mechanistic basis, the early data are promising, and the field needs more rigorous comparative clinical studies before definitive claims about magnitude of effect are justified. Anyone presenting this technology as fully proven is getting ahead of the evidence. And anyone dismissing it as pure marketing is probably not reading the primary literature closely enough. Both positions miss the actual state of the science.

Sources

• Lipid-Based Drug Delivery Systems for Cannabinoids, National Library of Medicine (NCBI/PMC)
• Pharmaceutical Development Guidance (ICH Q8 aligned), Therapeutic Goods Administration
• Oral Bioavailability of Cannabinoids: Formulation Strategies; National Library of Medicine (NCBI/PMC)
• Cannabidiol Products: Information for Sponsors, Therapeutic Goods Administration

, Tom Whitfield, Health librarian, references & fact-checking