Eszopiclone, sold under the brand-name Lunesta among others, is a medication used in the treatment of insomnia. Evidence supports slight to moderate benefit up to six months. It is taken by mouth.Common side effects include headache, dry mouth, nausea, and dizziness. Severe side effects may include suicidal thoughts, abuse, hallucinations, and angioedema. Greater care is recommended in those with liver problems and older people. Rapid decreasing of the dose may result in withdrawal. Eszopiclone is classified as a nonbenzodiazepine sedative hypnotic and as a cyclopyrrolone. It is the S-stereoisomer of zopiclone.