Risperidone is an antipsychotic medication. It is mainly used to treat schizophrenia, bipolar disorder, and irritability in people with autism. Risperidone is effective in treating the acute exacerbations of schizophrenia. Second generation antipsychotics, including risperidone, are effective in the treatment of manic symptoms in acute manic or mixed exacerbations of bipolar disorder. Compared to placebo, risperidone treatment reduces certain problematic behaviors in autistic children, including aggression toward others, self-injury, temper tantrums, and rapid mood changes. The evidence for its efficacy appears to be greater than that for alternative pharmacological treatments

Risperidone is an antagonist of the Dopamine receptors D1 as well as the D2 family receptors. This drug has "tight binding" properties, which means it has a long half-life and like other antipsychotics, risperidone blocks the mesolimbic pathway, the prefrontal cortex limbic pathway, and the tuberoinfundibular pathway in the central nervous system. Risperidone may induce extrapyramidal side effects, akathisia and tremors, associated with diminished dopaminergic activity in the striatum. Risperidone also interacts with Serotonin receptors, Alpha α1 adrenergic receptors, Alpha α2 adrenergic receptors and Histamine H1 receptors which may account for its its orthostatic hypotensive effects, greater positive, negative, affective and cognitive symptom control and account for its sedation and reduction in vigilance.

In 2012, Johnson & Johnson and its subsidiary Janssen Pharmaceuticals Inc. were fined $1.2 billion by Judge Timothy Davis Fox of the Sixth Division of the Sixth Judicial Circuit of the U.S. state of Arkansas. The jury found the companies had downplayed multiple risks associated with risperidone (Risperdal). The verdict was later reversed by the Arkansas State Supreme court. In August 2012, Johnson & Johnson agreed to pay $181 million to 36 U.S. states in order to settle claims that it had promoted risperidone and paliperidone for off-label uses including for dementia, anger management, and anxiety. In November 2013, J&J was fined $2.2 billion for illegally marketing risperone for use in people with dementia. J&J has faced numerous civil lawsuits on behalf of children who were prescribed risperidone who grew breasts (a condition called gynecomastia); as of July 2016 there were about 1,500 cases in Pennsylvania state court in Philadelphia, and there had been a February 2015 verdict against J&J with $2.5 million awarded to a man from Alabama, a $1.75M verdict against J&J that November, and in 2016 a $70 million verdict against J&J

Formal Chemical Name (IUPAC)
3-[2-[4-(6-fluoro-1,2-benzoxazol-3-yl)piperidin-1-yl]ethyl]-2-methyl-6,7,8,9-tetrahydropyrido[1,2-a]pyrimidin-4-one

References

https://en.wikipedia.org/wiki/Risperidone