Background: Adjuvants play an important role in enhancing the quality of anesthesia and also in reducing the requirement of primary anesthetic and its related adverse events. Calcitonin is one such adjuvant. But there is still uncertainty regarding the appropriate dose of calcitonin to achieve maximum analgesic efficacy and safety. The current study is conducted to add to the existing evidence on the subject and was aimed to compare the efficacy and safety of two different doses of calcitonin as an adjuvant in patients undergoing spinal anesthesia.Methods: A prospective randomized controlled double-blind trial was conducted in the Department of Anesthesiology and Intensive Care, Sir Sunderlal Hospital, Banaras Hindu University from May 2006 to May 2007. A total of 80 participants aged between 18 to 60 years, with ASA I and II physical status, undergoing infra-umbilical surgeries were randomly allocated to one of the 4 intervention groups. All the 4 intervention groups received 0.5% bupivacaine (H) 3ml as a primary anesthetic agent. Group I and III received 50 IU and 100 IU salmon calcitonin as an adjuvant. Group II received placebo and group IV (control) received no adjuvant. Pinprick test, Bromage scale and 10-point Visual analog scale (VAS) were used to measure the efficacy.Results: All the study groups were comparable with respect to all baseline variables. The time interval to the first dose of analgesia was longest in 100 I.U. calcitonin group, followed by 50 I.U. calcitonin group, placebo control group. The mean duration of analgesia (in minutes) among group I (100I.U. calcitonin) was 230.00±92.39, 159.25±21.59 among group II (Placebo), 161.50±31.20 among group III (50 I.U. calcitonin) and 142.75±20.22 among group IV. Considering group IV (control group) as base line. The differences of duration of analgesia (in minutes) in group I, group II and group III with baseline value (group IV) were statistically significant (P value <0.05). Even though the proportion of subjects developing adverse events was slightly higher in 100 I.U calcitonin groups compared to other groups, they were minor adverse events and were managed appropriately. There were no significant differences across the study groups in terms of hemodynamic stability.Conclusions: Salmon calcitonin as adjuvant increases the duration of postoperative analgesia. Even though the there slightly higher incidence of adverse events with 100 I.U calcitonin they are minor and the risk-benefit ratio favors calcitonin use. To make a categorical recommendation on the appropriate dose, there is further need for large-scale studies and pooled analysis.