THCA (tetrahydrocannabinolic acid) is a phytocannabinoid acid, an inactive form found in a fresh cannabis plant. THCA turns into THC (delta-9-tetrahydrocannabinol) when sufficient heat is applied. Therefore, contrary to popular belief THC is not actually present in fresh cannabis plants. Heating THCA to temperatures above 100ºC causes decarboxylation (releasing CO2), converting the acid into their bioactive form THC.

THC is psychoactive, euphorigenic, and has intoxicating effects at high doses. In the body, THC is converted to a potent psychoactive metabolite, 11-hydroxy-THC (11-OH- THC).

Current prescribing indicates that cannabis-based medicines containing THC or THC:CBD are mainly used in the context of pain, oncology, or palliative care settings. Clinical benefits are observed in conditions such as pain, nausea, and vomiting.

Cannabidiolic acid

Another abundant acid form is cannabidiolic acid (CBDA). The active form is CBD (cannabidiol). CBD is psychoactive but does not have intoxicating effects.

Source: Clinical primer – A guide to the rational use of cannabis-based medicines