indication

Used for the control of nausea and vomiting, caused by chemotherapeutic agents used in the treatment of cancer, in patients who have failed to respond adequately to conventional antiemetic treatments.

pharmacology

Nabilone is a cannabinoid with therapeutic uses. It is an analog of dronabinol (also known as tetrahydrocannabinol or THC), the psychoactive ingredient in cannabis. It is reserved for use in individuals who do not respond to the more commonly used anti-emetics. This is mainly because cannabinoids have potential adverse effects similar to that of cannabis and may cause changes in mood and behaviour.

mechanism of action

The mode of action of nabilone has been studied in cats and dogs. Although its anti-emetic action is not yet fully understood, it is apparent that there are a number of points in the control systems of the body at which Nabilone could block the emetic mechanism. It is likely that nabilone exerts its actions via binding to the cannabinoid receptors.

toxicity

Symptoms of overdose include difficulty in breathing, hallucinations, mental changes (severe), nervousness or anxiety (severe). Monkeys treated with Nabilone at doses as high as 2mg/kg/day for a year experienced no significant adverse events. This result contrasts with the finding in a planned 1-year dog study that was prematurely terminated because of deaths associated with convulsions in dogs receiving as little as 0.5mg/kg/day. The earliest deaths, however, occurred at 56 days in dogs receiving 2mg/kg/day. The unusual vulnerability of the dog is not understood; it is hypothesised, however, that the explanation lies in the fact that the dog differs markedly from other species (including humans) in its metabolism of Nabilone.

biotransformation

Hepatic. Two metabolic pathways have been suggested. The major pathway probably involves the direct oxidation of Nabilone to produce hydroxylic and carboxylic analogues. These compounds are thought to account for the remaining plasma radioactivity when carbinol metabolites have been extracted.

absorption

Rapidly absorbed from the gastrointestinal tract following oral administration.

half life

2 hours, with metabolites around 35 hours.

route of elimination

The route and rate of the elimination of nabilone and its metabolites are similar to those observed with other cannabinoids, including delta-9-THC (dronabinol). Therefore, it appears that the major excretory pathway is the biliary system.

drug interactions

Trimethobenzamide: Anticholinergics, such as Trimethobenzamide, may increase the tachycardic effect of cannabinoids such as Nabilone. Close monitoring of cardiovascular effects is recommended.

Triprolidine: The CNS depressants, Triprolidine and Nabilone, may increase adverse/toxic effects due to additivity. Monitor for increased CNS depressant effects during concomitant therapy.

Trospium: Anticholinergics, such as Trospium, may increase the tachycardic effect of cannabinoids such as Nabilone. Close monitoring of cardiovascular effects is recommended.