Cannabinoid Disposition After Human Intraperitoneal Use: An Insight Into Intraperitoneal Pharmacokinetic Properties in Metastatic Cancer
Background: Medicinal cannabis is prescribed under the provision of a controlled drug in the Australian Poisons Standard. However, multiple laws must be navigated in order for patients to obtain access and imported products can be expensive. Dose-response information for both efficacy and toxicity pertaining to medicinal cannabis is lacking. The pharmacokinetic properties of cannabis administered by traditional routes has been described but to date, there is no literature on the pharmacokinetic properties of an intraperitoneal cannabinoid emulsion.
Case description: A cachectic 56-year-old female with stage IV ovarian cancer and peritoneal metastases presented to hospital with fevers, abdominal distension and severe pain, vomiting, anorexia, dehydration and confusion. The patient reported receiving an intraperitoneal injection, purported to contain 12 g of mixed cannabinoid (administered by a deregistered medical practitioner) two days prior to presentation. Additionally, cannabis oil oral capsules were administered in the hours prior to hospital admission.
Results: THC concentrations were consistent with the clinical state but not with the known pharmacokinetic properties of cannabis nor of intraperitoneal absorption. THC concentrations at the time of presentation were predicted to be ∼60 ng/mL. Evidence suggests that blood THC concentrations > 5 ng/mL are associated with substantial cognitive and psychomotor impairment. The predicted time for concentrations to drop < 5 ng/mL was 49 days after administration.
Discussion: The unusual pharmacokinetic properties of the case suggest that there is a large amount unknown about cannabis pharmacokinetic properties. The pharmacokinetic properties of a large amount of a lipid soluble compound given intraperitoneally gave insights into the absorption and distribution of cannabinoids, particularly in the setting of metastatic malignancy.