Adjuvant effect of melatonin on anesthesia induced by thiopental sodium in human subjects

Background: Melatonin has unique properties of anxiolysis, hypnosis, and analgesia without impairing psychomotor skills. We studied the dose requirements of thiopentone for induction of general anesthesia following administration of oral melatonin compared to that of placebo. Methods: The study is a prospective randomized double-blinded study conducted at Sri Ramachandra Medical College, which included 44 patients of ASA status I and II in the age group of 16 to 55 years who underwent elective surgical procedures under general anesthesia. Patients were randomly allocated to 2 groups by drawing lots. Group A received T. Melatonin 0.2mg/kg and Group B received placebo 120 minutes prior to induction of anesthesia. The baseline heart rate, blood pressure, Spo2 and Ramsay sedation score were noted down. After adequate preoxygenation, all patients received Injection Fentanyl 2 mcg/kg followed by Inj. Thiopentone 2.5% which was titrated to loss of eyelash reflex. The dose of thiopentone required was noted down in both the groups. Hemodynamic parameters (HR, Systolic and diastolic BP) were monitored prior to induction and every 3 minutes for the first 10 minutes. Results: Both the groups were comparable with regard to age, weight and ASA status. Ramsay sedation score prior to induction of anesthesia was not significantly different in both the groups. The mean dose of Thiopentone required in Group A (Melatonin) was 138.64±6.3 mg and 223.86±5.3 mg in Group B (Placebo) with P value 0.000. The mean per Kg dose requirement of Thiopentone in Group A was 2.54±0.64mg and 4.56±0.67mg in Group B (placebo) with P value 0.000. Hemodynamic parameters were similar in both the groups. Conclusions: Administration of melatonin 0.2mg/kg body weight significantly reduced the induction dose of Thiopentone.