Volunteers taking cannabis-based therapeutic drugs as part of a controlled trial, which had been approved by an ethics board as safe for the subjects, experienced psychotic effects just as strong as if they had smoked cannabis. These findings, highly unexpected in such a controlled environment, are published today in the peer-reviewed, Open Access journal BMC Psychiatry.
Dr Bernard Favrat and colleagues, from the Institut Universitaire de Medecine Legale in Switzerland, were conducting a clinical trial into the effects of orally administered delta-9-tetrahydrocannibol (THC), the active ingredient in cannabis, when two of their male subjects experienced impaired psychomotor functions and severe anxiety typical of cannabis-induced psychosis.
When smoking cannabis, the effects of THC on psychomotor functions usually start once the concentration in the blood has reached 10ng/ml plasma. The trial should have been safe as the subjects were given low doses of THC and had much lower concentrations in their blood. However the two male subjects experienced their reactions with blood concentrations of 4.7ng/ml and 6.2 ng/ml, respectively.
Favrat and colleagues found that both subjects reported severe anxiety and impaired psychomotor functions. Other effects included transient symptoms of derealisation and depersonalisation, and paranoid delusions. They were described by one subject as worse than those experienced after smoking cannabis. One subject was given dronabinol, a synthetic THC that has been in medical use in the USA since 1985. The other subject was asked to drink a decoction of natural THC. The authors hypothesise that the effect may have been because the THC had been ingested, rather than inhaled; digesting THC may produce potent THC metabolites, which induce psychotic effects.