Goal & Background: This research was aimed at comparing the effect, onset and duration of sensory and motor block, hemodynamic effects, analgesic effects and the adverse effects of intrathecal dexmedetomidine, fentanyl and magnesium sulphate to 0.5% hyperbaric bupivacain. Methods: the research is done on 60 ASA I or II patients aged 18 to 60 years planned for the lower abdominal procedure under a spinal anaesthetic, randomly assigned to four equal groups (25 patients each) by means of a computer generated random number table: Group I: 15 mg of 0.5 percent intrathecally hyperbolic bupivacaine +0.5 ml of normal saline received. Group II: 15 mg 0.5% hyperbaric + 50 mg MgSO4 intrathecally received. Group III: 15mg hyperbaric bupivacaine Plus 25μg intrathecally of fentanyl. Group IV: receives 15 mg of 0.5 percent hyperbaric bupivacaine and 5 μg of diluted intrathecally dexmedetomidine. Results and Conclusion: Magnesium sulphate has a speedier start, although both fentanyl and dexmedetomidine have a longer duration and an enhanced block power. As a local anaesthetic addition, magnesium and dexmedetomidine may have fewer side effect than fentanyl. Intrathacal injection with bupivacaine of dexmedetomidine and MgSO4 was beneficial in lowering the occurrence of post-SA tearing. We are thus encouraging the use of MgSO4 since it is more physiologically available, more accessible and considerably cheaper than dexmedetomidine in most operating theatres. Magnesium offers hemodynamic stability, with less side effects than fentanyl.