The research will be carried out in order to test the effect of Intramuscular (IM) Diclofenac, administered as preemptive analgesic with minimal effective dose spinal anesthesia in perianal surgeries, on prolonging the time to first request for analgesic and lowering analgesic consumption. Investigators hypothesized that using IM Diclofenac in this surgery will postpone the time to first analgesic request and will decrease the consumption of post-operative analgesics. Our method includes dividing the patients into control and study groups and recording the first analgesic request and post-operative analgesic consumption after surgery and comparing the results.

Effective control of post-operative pain is an issue that has been repeatedly emphasized and has received an increasing amount of attention in the past few years (1, 2). Opioids, despite their side effects, are still the main cornerstone in managing acute postoperative pain (3). Preemptive analgesia refers to the administration of effective analgesia prior to surgical trauma. The main mechanism of preemptive analgesia is desensitization of the central nervous system and prevention of pain before its onset. (3). Non-opioid preemptive analgesics are commonly used to increase analgesic efficacy and patient satisfaction as well as to reduce opioid consumption and side effects. Saddle anesthesia is a selective spinal anesthesia that is commonly used for perianal surgeries (4-7).

Investigators previously performed a prospective up-down sequential allocation study to evaluate the minimum effective dose of hyperbaric bupivacaine that is needed for inducing a satisfactory and reliable saddle block for perianal surgeries that was restricted to the most caudal spinal nerve roots (S4-coccygeal) that supply the perianal region (8). Although the block produced no motor block in the lower limbs (thus allowing early ambulation), rapid sensory recovery resulted in early request of analgesia and increased opioid consumption. In this prospective, randomized, double blinded, placebo controlled clinical trial, Investigators hypothesize that a single dose of IM diclofenac administered before spinal anesthesia, will decrease postoperative pain, and delay and reduce postoperative analgesic requirement in patients undergoing minor perianal surgeries under minimal effective-dose bupivacaine saddle block

Inclusion Criteria:

• American Society of Anesthesiologists physical status I and II scheduled for elective outpatient perianal surgery in the lithotomy position (hemorrhoidectomy, fistulectomy)

Exclusion Criteria:

• contraindications to regional anesthesia, bleeding disorders, are morbidly obese, suffer from mental health problems, are on analgesic medication or psychotropic drugs, have a known history of allergy to amide local anesthetic drugs, if there is a language barrier, or if they are unwilling to participate

The studied drugs will be prepared immediately before injection by an anesthesiologist blinded to the study methodology and will be administered by a second blinded anesthesiologist patients and assessor also will be unaware of the type of group