Tramadol (HCl) is a centrally-acting analgesic with a unique, dual mechanism of action, within the CNS; it exerts agonistic properties at opiate receptors and interferes with neurotransmitter reuptake.Tramadol also binds weakly to µ-opiate receptors blocking the transmission of pain signals to the brain. It was originally thought that the drug had negligible abuse potential, but after its marketing, reports of drug abuse and withdrawal have been noted. The WHO guidelines indicate there is a place for tramadol in controlling moderate, but not severe, cancer pain.Tramadol has been effective in the control of post-operative pain, but is not suitable as an adjunct to anesthesia because of low sedative properties. Comparative studies with other analgesics for the treatment of postoperative pain indicate that tramadol is equivalent in potency to meperidine, one fifth as potent as nalbuphine, and one thousandth as potent as fentanyl. Respiratory depression caused by tramadol is less than that caused by morphine or meperidine but is apparent after overdose.