Final answer:
Risperidone is the medication expected to reduce agitation in a dementia patient with severe symptoms, as it is an antipsychotic drug that helps manage psychotic disorders.
Step-by-step explanation:
The medication that would be expected to reduce agitation in a client with dementia who is experiencing agitation, violence, and bizarre thoughts is risperidone. Risperidone is an antipsychotic drug that can diminish aggressive and impulsive behavior and help to alleviate psychotic symptoms such as hallucinations and delusions.
While diazepam is a tranquilizer that could also help reduce anxiety and tension, risperidone is specifically mentioned as an antipsychotic added in 1994 that antagonizes D2 and serotonin type 2 receptors along with other types of receptors, making it more suitable for managing symptoms associated with psychotic disorders.