Spinal anesthesia is the most commonly used technique for lower abdominal surgeries as it is very economical and easy to administer.  A number of adjutants, such as Opioids , Clonidine, and Midazolam have been studied to prolong the effect of spinal anesthesia (ELIA , et al 2008).
      Dexmedetomidine a new highly selective a2- agonist is under evaluation as a neuraxial adjuvant as it provides stable hemodynamic conditions, good quality of intraoperative and postoperative analgesia with minimal side effects(Kanazi and Al-Ghanem 2009).
     Magnesium sulfate (Mg)  is an antagonist of N-methyl D Aspartate receptor (NMDA) improves postoperative analgesia after intrathecal administration as an effective adjuvant to bupivacaine (Soave  and  Arcangeli  2009).
Aim of the work
      To compare the postoperative analgesic effects and any side effects ofdexmedetomidine and magnesium sulfate (Mg) when added to bupivacaine in spinal anesthesia in patientsundergoing perianal surgeries.
Patients and methods
     Ninty ASA physical status I and II patients aged 18-70 years, of either sex, scheduled for perianal surgeries under spinal anesthesia in this prospective randomized, double-blinded study.
Results
       All the Mg cases needed analgesia within 4 hours postoperative, while for all the Dex cases needed analgesia within5 hours postoperative. The difference between the two groups was highly significant.