Enhancing the activity of cannabidiol and other cannabinoids in vitro through modifications to drug combinations and treatment schedules.

Cannabinoids are the bioactive components of the Cannabis plant that display a diverse range of therapeutic qualities. We explored the activity of six cannabinoids, used both alone and in combination in leukaemic cells. Cannabinoids were cytostatic and caused a simultaneous arrest at all phases of the cell cycle. Re-culturing pre-treated cells in drug-free medium resulted in dramatic reductions in cell viability. Furthermore, combining cannabinoids was not antagonistic. We suggest that the activities of some cannabinoids are influenced by treatment schedules; therefore, it is important to carefully select the most appropriate strategy in order to maximise their efficacy.