Mr. Feisty has mild Alzheimer's disease (AD) diagnosed 2 years ago after progressive short-term memory decline. His wife reports that over the last three weeks he has shown irritable mood, anhedonia, early-morning awakening, low energy, reduced appetite with ~5 lb (2.3 kg) loss, and difficulty concentrating beyond his baseline cognitive impairment. He has skipped two community senior-center activities he previously enjoyed. No hallucinations or delusions. He denies active suicidal intent but says. "Sometimes I wonder if it would be easier if I didn't wake up." No recent illness, fever, or falls. No alcohol or illicit drug use. Which is a first-line medication option for treating depression in an elderly patient

A. Olanzapine (Zyprexa): Olanzapine is an atypical antipsychotic primarily used to manage psychosis and severe mood disorders. In older adults, it carries increased risks such as metabolic effects, sedation, and cerebrovascular events. It is not used as an initial treatment for depression in the elderly. B. Memantine (Namenda): Memantine is indicated for moderate to severe Alzheimer’s disease and works by modulating glutamate activity. It does not target depressive symptoms such as anhedonia, low mood, or sleep disturbance. Its use is unrelated to treatment of mood disorders. C. Haloperidol (Haldol): Haloperidol is a typical antipsychotic used to manage acute agitation or psychosis. In elderly clients, it is associated with extrapyramidal symptoms and increased mortality risk, particularly in those with dementia. It does not address the core features of depression. D. Fluoxetine (Prozac): Fluoxetine is a selective serotonin reuptake inhibitor commonly used to treat depression. SSRIs are considered first-line therapy in older adults due to their favorable safety profile compared to tricyclic antidepressants. This class targets mood, sleep, energy, and appetite changes seen in depression.