A nurse is assessing a client following treatment for serotonin syndrome caused by an antidepressant medication. Which of the following findings indicates the treatment has been effective?

A. Decrease in blood pressure: A decrease in blood pressure is a positive sign that the treatment for serotonin syndrome is effective. Treatment typically includes discontinuing the causative medication and providing supportive care to normalize vital signs, including blood pressure. B. Muscle rigidity: Muscle rigidity is a hallmark sign of serotonin syndrome and indicates that the condition is still present or not yet effectively treated. Successful treatment should reduce muscle rigidity over time. C. Hyperreflexia: Hyperreflexia (overactive reflexes) is also a common symptom of serotonin syndrome. If the treatment is effective, hyperreflexia should resolve as serotonin levels normalize in the body. D. Altered mental status: Altered mental status is another indicator of serotonin syndrome. Improvement in serotonin syndrome would be evidenced by a return to normal cognitive function, so persistence of altered mental status suggests that treatment has not yet been fully effective.