- Anorexia (HIV/AIDS)
- Nausea / vomiting (CHEMOTHERAPY)
- Neuropathic Pain (MS)
- Spasticity (MS)
- Overactive Bladder (MS)
Tetrahydrocannabinol abbreviated as THC is one of at least 113 natural and active Cannabinoids identified in Cannabis. Whilst a psychotropic cannabinoid (dronabinol, trade names Marinol and Syndros are a synthetic form of THC, approved by the FDA) and is the principal psychoactive constituent of cannabis. Dronabinol is the INN for a pure isomer of THC, (−)-trans-Δ⁹-tetrahydrocannabinol, which is the main THC isomer found in cannabis. Its chemical name is (−)-trans-Δ⁹-tetrahydrocannabinol, and the term THC is used to refer to isomers as well. The pharmaceutical formulation dronabinol is available by prescription in the US, Canada, Germany, and New Zealand. The prescriptions Marinol, Syndros, and Sativex also include THC or its isomers as active ingredients.[clarification needed]
Like most pharmacologically-active secondary metabolites of plants, THC is a lipid found in Cannabis, assumed to be involved in self-defense, perhaps against insects. THC also possesses high UV-B (280–315 nm) absorption properties, which, it has been speculated, could protect the plant from harmful UV radiation exposure.
THC, along with its double bond isomers and their stereoisomers, is one of only three cannabinoids scheduled by the UN Convention on Psychotropic Substances (the other two are dimethylheptylpyran and parahexyl). It was listed under Schedule I in 1971, but reclassified to Schedule II in 1991 following a recommendation from the WHO. Based on subsequent studies, the WHO has recommended the reclassification to the less-stringent Schedule III. Cannabis as a plant is scheduled by the Single Convention on Narcotic Drugs (Schedule I and IV). It is specifically still listed under Schedule I by US federal law under the Controlled Substances Act passed by the US Congress in 1970.
Dronabinol is the INN for a pure isomer of THC, (−)-trans-Δ⁹-tetrahydrocannabinol, which is the main THC isomer found in cannabis. It is used to treat anorexia in people with HIV/AIDS as well as for refractory nausea and vomiting in people undergoing chemotherapy. It is safe and effective for these uses.
THC is also an active ingredient in nabiximols, a specific extract of Cannabis that was approved as a botanical drug in the United Kingdom in 2010 as a mouth spray for people with multiple sclerosis to alleviate neuropathic pain, spasticity, overactive bladder, and other symptoms.
A meta analysis of clinical trials conducted using standardized cannabis extracts or THC conducted by the American Academy of Neurology found that of 1619 persons treated with cannabis products (including some treated with smoked cannabis and nabiximols), 6.9% discontinued due to side effects, compared to 2.2% of 1,118 treated with placebo. Detailed information regarding side effects was not available from all trials, but nausea, increased weakness, behavioral or mood changes, suicidal ideation, hallucinations, dizziness, and vasovagal symptoms, fatigue, and feelings of intoxication were each described as side effects in at least two trials.