Trazodone is an antidepressant medicine mainly used to treat major depressive disorder and is also often prescribed for anxiety and insomnia because of its calming, sleep-promoting effect. It belongs to the serotonin antagonist and reuptake inhibitor (SARI) class, meaning it increases serotonin activity while blocking certain serotonin receptors, and it also blocks histamine and alpha-1 adrenergic receptors, contributing to its sedative properties. It is taken orally, usually as tablets, and is sometimes used off-label for conditions like PTSD-related sleep problems and certain chronic pain or fibromyalgia.