The Pharmacokinetics of Δ9-Tetrahydrocannabinol in Sheep

Abstract

The pharmacokinetics of Δ9-tetrahydrocannabinol (Δ9-THC) has not been established in ruminants. Pharmacokinetic knowledge is important given feeding industrial hemp biomass has been shown to result in tissue residues post feeding in sheep. Due to a lack of testing and available data, a ‘maximum’ concentration of Δ9-THC has not been currently set for foods of animal origin. Consequently, this study was designed to gain a better understanding of how ruminants process Δ9-THC. Eight Merino ewes were administered with two per os (PO) doses of 88.5 mg Δ9-THC/kg bodyweight (BW) 12 h apart. Blood samples were collected periodically post dosing to determine the pharmacokinetics of Δ9-THC and subcutaneous fat biopsies were taken to investigate the deposition and elimination of Δ9-THC from sheep. An elimination half-life of 31.40 ± 13.87 h was identified, with residues persisting in the subcutaneous fat for 28 d in five of the eight sheep, before decreasing below the limit of detection in all sheep by 91 d. These results support the prolonged presence of Δ9-THC residues previously identified. Thus, imposing a practical withholding period for ruminants involved in the food chain may not be possible, with further research required to investigate how iHemp biomass may be safely fed to ruminants.