Antipsychotic

An antipsychotic is a prescription medication that reduces hallucinations, delusions and disordered thinking, mainly by blocking dopamine D2 receptors in the brain.

First-generation antipsychotics such as haloperidol act strongly on dopamine receptors and frequently cause movement side effects including tremor, stiffness and tardive dyskinesia. Second-generation drugs such as risperidone, olanzapine, quetiapine and aripiprazole also act on serotonin receptors and carry more metabolic side effects such as weight gain and elevated blood sugar. Antipsychotics are used for schizophrenia, bipolar disorder, psychotic depression and, off label, for severe agitation.

Cannabidiol has been tested as a candidate antipsychotic in a small number of clinical trials in schizophrenia, both alone and added to existing medication, and it does not act through dopamine blockade, which makes its mechanism of interest. Those trials are early and results are mixed. THC, by contrast, can worsen psychosis and is associated with earlier onset in vulnerable people. Cannabidiol also inhibits liver enzymes that metabolize several antipsychotics, so drug-drug interactions are possible.