Effects of delta-9-tetrahydrocannabinol administered subcutaneously to rabbits for 28 days

Propylene glycol and Kolliphor as solvents for systemic delivery of cannabinoids via intraperitoneal and subcutaneous routes in preclinical studies: a comparative technical note

BACKGROUND

Substance administration to laboratory animals necessitates careful consideration and planning in order to enhance agent distribution while reducing any harmful effects from the technique. There are numerous methods for administering cannabinoids; however, several parameters must be considered, including delivery frequency, volume of administration, vehicle, and the level of competence required for staff to use these routes properly. There is a scarcity of information about the appropriate delivery method for cannabinoids in animal research, particularly those that need the least amount of animal manipulation during the course of the investigation. This study aims to assess the feasibility and potential side effects of intraperitoneal and subcutaneous injection of CBD and THC using propylene glycol or Kolliphor in animal models. By evaluating the ease of use and histopathological side effects of these solvents, this study intends to help researchers better understand an accessible long-term delivery route of administration in animal experiments while minimizing the potential confounding effects of the delivery method on the animal.

METHODS

Intraperitoneal and subcutaneous methods of systemic cannabis administration were tested in rat models. Subcutaneous delivery via needle injection and continuous osmotic pump release were evaluated using propylene glycol or Kolliphor solvents. In addition, the use of a needle injection and a propylene glycol solvent for intraperitoneal (IP) administration was investigated. Skin histopathological changes were evaluated following a trial of subcutaneous injections of cannabinoids utilizing propylene glycol solvent.

DISCUSSION

Although IP delivery of cannabinoids with propylene glycol as solvent is a viable method and is preferable to oral treatment in order to reduce gastrointestinal tract degradation, it has substantial feasibility limitations. We conclude that subcutaneous delivery utilizing osmotic pumps with Kolliphor as a solvent provides viable and consistent route of administration for long-term systemic cannabinoid delivery in the preclinical context.

Teratologic evaluation of synthetic delta 9-tetrahydrocannabinol in rabbits

Synthetic delta 9-tetrahydrocannabinol (THC) was dissolved in undiluted propylene glycol and administered in daily subcutaneous doses of 15.0, 30.0 or 60.0 mg/kg to pregnant New Zealand white rabbits on days 7--19 of gestation. Maternal food consumption and weight gain were markedly reduced at all dose levels. Embryotoxicity and embryocidal effects were observed in the form of reduced litter weight and number of viable fetuses, respectively, in offspring from pregnant mothers treated with THC. However, on the basis of extensive external, visceral and skeletal examination of all fetuses it may be concluded that THC is not teratogenic in the New Zealand white strain rabbit following subcutaneous administration of doses as high as 60.0 mg/kg/day during the critical period of organogenesis (days 7--19 of gestation). On the other hand, an oral dose of thalidomide (200.0 mg/kg/day), the positive control used in this study, was both embryocidal and teratogenic.

Toxicity of delta9 -tetrahydrocannabinol (THC) administered subcutaneously for 13 days to female rabbits

Delta9- Tetrahydrocannabinol (THC) was administered subcutaneously to female New Zealand white strain rabbits for 13 days. The animals were randomly divided into six groups of five animals each of which consisted of untreated controls, vehicle (undiluted propylene glycol)-treated, and THC treatment at dose levels of 100, 30, 10, and 3 mg/kg/day. All animals survived for the duration of the study. The THC-treated rabbits did not gain significant body weight which seems to be due to a decreased food consumption. There were some variations in various hematologic values, but they all were within the normal range for our laboratory. Blood chemistry evaluations showed decreased serum levels of potassium, glucose, blood urea nitrogen, alkaline phosphatase, and albumin/globulin (A/G) ratio and an increase in cholesterol levels of all treated animals. A significant increase in billirubin values was noted in the animsls of the 3- and 10-mg/kg groups. The injection site in the skin of the THC-treated rabbits showed signs of local irritation (erythema and subcutaneous abscesses). There was a reduction in absolute and percent of body weight of the liver and absolute weight of the lungs of the treated animals. However, no histopathologic alterations were observed. It may be concluded that THC treatment subcutaneously for 13 days in rabbits up to a dose level of 100 mg/kg/day did not produce any significant toxicity, except anorexia and some local dermal irritation.