Potentially dangerous symptoms that can occur when antidepressants are taken with other medicines that also raise serotonin levels.

Serotonin syndrome can result from taking medicines, illicit drugs or herbal supplements that increase serotonin levels. It may occur after starting a new medicine, increasing the dose of a medicine or combining medicines.

Minor serotonin syndrome symptoms can include confusion, rapid heart rate and sweating. Dangerous symptoms may include high fever and seizures. Symptoms may occur within hours of taking certain medicines.

Treatment usually involves stopping the medicine that's causing the symptoms. Sometimes medicines may be needed to block serotonin. Dangerous symptoms may need to be treated in a hospital.