Assessment of different mouthwashes on cannabis oral fluid concentrations

Since the implementation of mandatory drug testing in drivers' oral fluid, several solutions to avoid an onsite positive result can be found on drug users' forums, especially for marijuana, including the use of different mouthwashes. Recently, a product for personal hygiene, Kleaner, has been sold for this purpose. The aims of this study were to assess the effect of water, whole milk, and Kleaner mouthwashes on tetrahydrocannabinol (THC) oral fluid concentrations, and those observed in passive smokers subjected to extreme contamination conditions. The study was performed on four days. On day 0, study information was given to the participants. On days 1, 2, and 3, 11 chronic cannabis users smoked their usual daily dose, and oral fluid specimens were collected before smoking (t=-0.5h) and at t=0.25, 0.5, 1, 3, 6, 12, and 24 h post-smoking. On day 1, participants rinsed their mouth with water before each specimen collection. On day 2, 5 participants rinsed their mouth with Kleaner and 6 with whole milk. On day 3, a specimen was collected before and after rinsing the mouth with water. Statistically significant lower concentrations were observed comparing concentrations in oral fluid specimens collected before and after a water rinse. However, maximum THC concentrations at t=0.25 h were >3-fold higher than the cut-off employed by the Spanish police (25 ng/mL) regardless of the use of any mouthwash. THC was also detected in the oral fluid of passive smokers subjected to extreme contamination conditions; however, concentrations were <25 ng/mL in all cases.