Which of the following is NOT an effect of sibutramine?

Sibutramine is a medication primarily used for weight management by suppressing appetite and enhancing satiety. Its mechanism mainly involves the inhibition of the reuptake of certain neurotransmitters such as serotonin, norepinephrine, and dopamine, which induces a feeling of fullness and reduces the desire to eat.

The option related to increased energy levels does not accurately reflect the primary pharmacological effects of sibutramine. While some individuals might experience increased motivation for activity due to weight loss, it is not classified as a direct effect of the medication. Sibutramine does not stimulate energy levels as might be expected from other types of stimulants; its primary role is appetite suppression and satiety enhancement rather than serving as a source of increased energy.

In contrast, the other options accurately depict the effects of sibutramine. It effectively reduces appetite and enhances feelings of fullness by altering neurotransmitter activity, which are key components in its role as an anti-obesity agent. Thus, the choice indicating increased energy levels stands out as the correct option that does not describe an effect of sibutramine.