Pain is a multifaceted and complex neurosensory condition that involves biological, psychological and social factors [1]. The International Association for the Study of Pain (IASP) defines pain as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage” [2,3]. This neurosensory phenomenon impacts the quality of life and behavior negatively [4]. Pain is classified according to its duration and pathophysiology. Regarding duration, pain is divided into acute or chronic [5]. Acute pain is a biological response to short-term tissue injury, gradually decreasing as the body recovers, is treated or heals. Chronic pain is persistent and long-lasting, extending for more than 3 months and potentially lasting for years [6].

In terms of pathophysiology, IASP classifies pain into nociceptive, neuropathic and nociplastic [7]. Nociceptive pain involves the activation of nociceptors that detect actual or potential harmful stimuli and generate a reflex response. Neuropathic pain results from a lesion or disorder of the central nervous system (CNS) or peripheral nervous system (PNS). Nociplastic pain is defined by altered nociceptive processing in the absence of clear evidence of tissue damage or nervous system injury [5]. Due to its complexity, pain management requires a multifactorial approach. Conventional treatments involve combinations of different drugs, such as nonsteroidal anti-inflammatory drugs (NSAIDs), local anesthetics (LAs) and opioids [2,8]. However, such therapies often show limited efficacy in pain management [4].

In addition, the short duration of action of analgesics and LAs requires several doses, which can result in cardiovascular and neurological toxicity [9]. Similarly, NSAIDs exhibit partial efficacy and limited long-term use due to gastrointestinal, renal and cardiovascular toxicity [2]. Opioids induce severe adverse effects that limit its dosage and treatment duration, including cognitive impairment, physical dependence, addiction, tolerance, respiratory depression, constipation and risk of overdose [1,10].

Cannabis sativa L., commonly known as marijuana, ganja, or hemp, is an anemophilous species belonging to the Cannabaceae family and the Cannabis genus, recognized as one of the oldest plants cultivated by humanity [11]. It is an annual plant, mostly dioecious, occurring occasionally in a monoecious form. In this context, it has a straight, hollow stem, with a height ranging from 0.2 to 6.0 m (depending on the genotype, growing and environmental conditions). Female plants are typically more robust and thicker, whereas male plants tend to be more elongated. Notably, female plants are responsible for producing the inflorescences. The leaves are compound and palmate, oppositely or alternately arranged along the stem, ranging from 3 to 13 leaflets at the base and reducing to 1 to 3 in the apical region [12].

Cannabis stands out for its high chemical diversity, with over 130 phytocannabinoids already identified, belonging to the class of terpene phenolic compounds [13]. These compounds constitute the secondary metabolites, which are structurally characterized as oxygenated aromatic hydrocarbons, generally consisting of 21 carbon atoms. Among these compounds, Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD) stand out as the main constituents of plants [14]. Figure 1 displayed the chemical structure of CBD and THC.

THC is recognized as the main psychoactive compound present in Cannabis, also exhibiting therapeutic effects, such as analgesic action and appetite stimulation. However, its use may also be associated with adverse effects, including anxiety and episodes of paranoia [15]. This compound is formed through the decarboxylation of tetrahydrocannabinolic acid (THCA). It is a process that occurs during the drying of the plant after harvest. It can be intensified when subjected to heat, as during combustion (smoking), vaporization or cooking preparation [16].

In contrast, CBD has attracted growing interest due to its therapeutic potential in several neurological disorders. In addition, it does not induce psychoactive activity as THC does [17]. This compound is formed through the decarboxylation of cannabidiolic acid (CBDA), a process primarily induced by heating. It belongs to the class of terpenophenols, featuring in its structure a cyclohexene ring, a phenolic ring and a pentyl side chain [18].

Other cannabinoids have also been studied given their therapeutic potential. Several novel applications have been investigated. Among them, cannabigerol (CBG) stands out as a non-psychoactive compound with several relevant pharmacological properties, including antibacterial, antifungal and anti-inflammatory activities, increasing its potential for use in multipurpose clinical contexts [19]. Recent investigations have suggested that cannabinol (CBN) can exert antioxidant, anti-inflammatory and neuroprotective effects, reinforcing its pharmacological relevance [20]. Figure 2 illustrated the main cannabinoids found in Cannabis sativa and its distribution among different plant structures. The therapeutic effects of cannabinoids in Figure 2 were based on data already reported [21,22].

The biological activity of cannabinoids is associated with its interactions with the endocannabinoid system (ECS), a complex physiological signaling network widely distributed throughout the human body [23]. ECS consists of endogenous mediators, such as anandamide and 2-arachidonoylglycerol (2-AG), as well as its specific receptors (CB1 and CB2) and enzymes involved in biosynthesis and degradation, such as Fatty Acid Amide Hydrolase (FAAH) and Monoacylglycerol lipase (MAGL). The coordinated interaction among these components maintains the endocannabinoid tone, which is essential for the balance of several physiological processes and pathophysiological conditions throughout life [24]. In this communication system, the CB1 and CB2 receptors play essential roles in the transduction of endocannabinoid signals [25].

The CB1 receptor stands out as the most abundant G-protein-coupled receptor in the CNS. It is often described as the primary mediator of the psychoactive properties attributed to Cannabis [15]. In addition, CB1 is also present in the peripheral nervous system, particularly in sensory and sympathetic nerve endings, also participating in the regulation of nociception and gastrointestinal motility [26]. Moreover, the CB2 receptor is also a G-protein-coupled receptor. Its expression occurs in immunomodulatory cells, predominantly in glial cells and in the periphery, as well as leukocytes. Furthermore, its expression is dynamically regulated, increasing in response to inflammatory stimuli, particularly in microglia and brain-resident macrophages [27]. CB2 has gained increasing attention due to its role in the modulation of inflammatory, oxidative, immune and apoptotic processes. It is not associated with the adverse psychotropic effects, which generally occur with CB1 activation [28].

The nonpolar nature of cannabinoids directs the choice of appropriate methods for its extraction from Cannabis. It is generally employed organic solvents such as chloroform and alcohols (methanol and ethanol) or hydrocarbons such as butane and hexane [29]. In addition, decarboxylation process is an important step, once it converts cannabinoid acids into its neutral and bioactive forms, a process that also occurs through heating or during storage [30]. Through these procedures, the Cannabis sativa L. extract—the raw material—is obtained, in which the bioactive compounds responsible for the therapeutic effects are concentrated. From this extract, formulations in oil-based vehicles have been developed. However, the term “cannabis oil” lacks scientific precision, as it can refer both to the seed oil, which is free of relevant cannabinoids and to pharmaceutical preparations consisting of extracts diluted in oil [31]. In this context, standardization of extraction, purification and quantification processes become essential to ensure the quality control, stability, safety and efficacy of the cannabis-based processed forms [32].

Cannabis-based extract and oil are rich in cannabinoids that have demonstrated biological activity for conditions such as: chronic pain, CNS disorders, skin diseases, cancer and others [33,34]. Despite its high therapeutic potential, its application is limited by the susceptibility to environmental factors, such as oxygen, light, humidity and temperature, as well as the lipophilic nature of cannabinoids, resulting in its low solubility in physiological media [35].

The use of nanotechnology processing different nanocolloidal systems is useful to increase the physicochemical stability, solubility and bioavailability of entrapped molecules, resulting in optimized efficacy compared to free forms [36]. In this sense, the lipid nanoparticles can be designed as different nanocarriers with several supramolecular arrangements and modulable biophysical properties, being able to be administered through several routes [37]. All of these carriers have a strong ability to load highly hydrophobic molecules. There are some reports of cannabinoid encapsulation by liposomes (LUV), nanostructured lipid carriers (NLC) and nanoemulsions (NE) for human and veterinary clinical use, as illustrated in Figure 3.

The liposomal system is the pioneering lipid nanocarrier that has already been developed. There are some FDA-approved liposomal drugs, such as Doxil^® and Ambisome^®. LUV are composed of at least one phospholipid bilayer and cholesterol, surrounding an aqueous inner core. It is the most versatile nanocarrier, once it has affinity to encapsulate hydrophilic (aqueous core), hydrophobic (lipid bilayer) and amphiphilic (polar head and acyl chain interface) molecules. There are a lot of works that described LUV encapsulating highly hydrophobic molecules with success [38].

The second generation of lipid nanoparticles, known as NLC, configure the most developed nanocarrier based on natural lipids for multipurpose applications. This success is related to the nature of its structural matrix, which is composed of a blend of solid and liquid lipids, sterically stabilized by surfactants. Thus, natural lipids loaded by NLC exert a dual role in the formulations: structural and bioactive. The natural liquid lipid presence improves the nanoparticle arrangement, given by the formation of structural defections in the solid lipid matrix, which is required for this nanocarrier stability and efficacy [39]. Finally, NE are colloidal systems composed of liquid lipid and stabilized by surfactant and co-surfactant. Such systems have an affinity for loading natural lipids and exhibit long-term stability [40].

In this sense, the development of cannabis-based formulations have to ensure a set of structural parameters to warrant the quality control. A robust analytical method to quantify the cannabinoid upload indexes and the in vitro release profile is paramount. The monitoring of biophysical parameters has to be performed, in order to determine its shelf life. Then, only the systems with the best performance in all the above-mentioned requirements will be submitted to subsequent biological and preclinical assays. The cannabis-based nanodrug development has to include all these steps of analyses to provide a robust, safe and effective nanodrug.