Laparoscopic cholecystectomy (LC) is one of the commonly performed surgical procedures associated with a moderate degree of postoperative pain especially on the 1st postoperative day. Adequate postoperative analgesia allows early patient ambulation, decreases analgesic requirements, and hospital stay. Moreover, it has been hypothesized that intense acute pain after LC may predict development of chronic pain (e.g., post laparoscopic cholecystectomy syndrome). So, aggressive perioperative analgesia is needed.

the aim of the study is To compare the analgesic effect of magnesium sulfate combined with bupivacaine versus bupivacaine combined dexmedetomidine via OSCTAB block on postoperative pain control for 24 hours in patients scheduled for LC.

Transversus abdominis plane (TAP) block is a recent analgesic technique with efficacy in perioperative pain therapy for LC. It involves the infusion of local anesthetic into the fascial plane of the abdominal wall.

Oblique subcostal transversus abdominis plane (OSCTAP) block is an US-guided regional anesthesia technique that anesthetizes the nerves of the lower and upper anterior abdominal wall, specifically from T6 to L1. There weren't enough studies in the literature evaluating the OSCTAP block for pain management after LC.

Rafi et al and McDonnell et al were first to describe this novel abdominal field block. They described an anatomical landmark technique and provided evidence of blockade to the mid/lower thoracic and upper lumbar spinal nerves as they travelled in the fascial plane between the transversus abdominis (TA) and internal oblique (IO) muscles.

The OSCTAB block provides more effective analgesia than other TAP blocks. Numerous regional anesthetic adjuvants.

such as dexmedetomidine, clonidine, epinephrine, dexamethasone, and magnesium sulphate (MgSO4) are usually combined with enhancement of analgesic efficacy.

Recently, these adjuvants added to LA solution for prolonging the effect of TAP block with promising results.

Inclusion Criteria:

• • Patients programmed for elective LC.

  • American society of anesthesiologists (ASA) physical state I or II.
  • Age over 18 years and less than 60 years old.
  • Patients of both sex are included in the study.

Exclusion Criteria:

• •Patient refusal

  • Known hypersensitivity to the study drugs.
  • Body Mass Index > 40 kg/m2.
  • Inability to accurately describe postoperative pain to investigators.
  • Opioid tolerance or dependence.
  • Preexisting history of chronic pain.
  • History of renal, liver, cardiac, neuropsychiatric disorder problems.
  • Bleeding or coagulation abnormality.