Which drug's maximum dose is adjusted to half for a 2D6 poor metabolizer?

The correct choice focuses on aripiprazole, a medication metabolized primarily by the cytochrome P450 2D6 enzyme. Individuals who are categorized as 2D6 poor metabolizers have a reduced ability to metabolize drugs that rely on this pathway. This can lead to increased plasma concentration of substances such as aripiprazole, resulting in a heightened risk of side effects or toxicity. Consequently, it is recommended to adjust the maximum dose of aripiprazole, often to half, in these individuals to ensure safe and effective therapeutic use.

For the other options, while they may also have implications with regard to metabolic pathways, they do not specifically require the same degree of dose adjustment for 2D6 poor metabolizers. Atomoxetine, for example, is primarily metabolized by CYP2D6, but guidelines may not necessitate a dose adjustment of 50% based on poor metabolizer status as strictly as they do for aripiprazole. Citalopram and vortioxetine, while also affected by metabolic processes, do not have the same defined adjustments related to CYP2D6 poor metabolism as aripiprazole does. Thus, understanding aripiprazole's pharmacokinet