Inclusion Criteria:  Male and female Between 18 and 75 years old Reads and writes French Diagnosis of fibromyalgia syndrome according to Widespread Pain Index (WPI) and Symptom Severity Scale (SSS) score ≥ 13/31 Both molecules (Ketamine and Esketamine) were administered at least once during an analgesic infusion session in Pain Clinic Patient with regular medical follow-up by a pain specialist at least 3 times a year  Exclusion Criteria:  Allergy or intolerance to Ketamine or Esketamine Current infection, fever Pregnant or breastfeeding woman Serious cardiovascular disorders and severe hypertension Increased pressure of cerebrospinal fluid and severe intracranial disease Acute intermittent porphyria Untreated epilepsy Untreated glaucoma Difficult or impossible intravenous access Chronic Liver Disease Child-Pugh C