Gabapentin, a structural analog of gamma aminobutyric acid (GABA), was introduced within the us as an anticonvulsant, used clinically to treat epilepsy. The drug causes amino acids release within the medulla spinalis dorsal horn and thus decreasing response to neural inputs and stabilizing the nervous activity. The mechanism of action of gabapentin on neuropathic pain is assumed to bind to the alpha 2 delta subunit of the voltage-dependent calcium channel within the central systema nervosum , reducing calcium influx into the nerve terminals and decreases the release of neurotransmitters like glutamate . Gabapentin, therefore, can be used for controlling chronic pain, as in diabetic neuropathy and other neuropathic disorders . Some studies examined the effectiveness of gabapentin for acute postoperative pain management for gynecological surgery, lumbar spinal surgery, arthroplasty, and thoracic surgery . A recent study concluded that gabapentin has a role in preoperative anxiolysis, attenuation of hemodynamic response to intubation, prevention of postoperative nausea and vomiting (PONV) and finally postoperative delirium . Up to date, the effect of preoperative gabapentin on inhaled anesthetic depth is unknown

1. Inclusion criteria:

   • Patients aged from 18 to 60 years.
   • ASA I-II.
   • Undergoing craniotomy for intracranial tumors.

2. Exclusion criteria:

   • Patient refusal
   • Patients younger than 18 or above 60 years old
   • patients with (ASA) physical status ≥ III
   • patients with compromised cardiovascular, renal, hepatic or neurological function
   • Known allergy to study drug.
   • Contraindication or chronic use (consistent use for longer than 3 months) to any of the study drugs
   • Suffered from severe psychiatric disease or drug addiction;
   • History of parenteral or oral analgesic intake within the last 48hours

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