The Analgesic Effect of Gabapentin as a Prophylactic Anticonvulsant Drug on Postcraniotomy Pain: A Prospective Randomized Study

BACKGROUND: Gabapentin is an anticonvulsant drug that has analgesic properties for acute postoperative pain. However, the analgesic effect of gabapentin as an antiepileptic prophylactic drug on patients undergoing craniotomy is unclear. In this study, we evaluated the postoperative effectiveness of gabapentin on acute postoperative pain when it is used for antiepileptic prophylaxis in patients undergoing craniotomy for supratentorial tumor resection. METHODS: Eighty patients undergoing craniotomy for supratentorial tumor resection were randomly assigned into two groups. Patients in Group G (n = 40) received oral gabapentin (3 x 400 mg), and patients in Group P (n = 40) received oral phenytoin (3 x 100 mg) for 7 days before the operation and postoperatively. An identical anesthesia protocol was performed for both the groups. Anesthesia was maintained with propofol and remifentanil infusion. Patient-controlled analgesia with morphine was used, and pain levels were measured. The antiepileptic-related side effects, anesthetic consumption, duration of anesthesia and surgery, tracheal extubation time, postoperative pain scores, morphine consumption, and sedation scores were recorded. RESULTS: Thirty-seven patients in Group G and 38 patients in Group P completed the study. During the preoperative period in Group G, one patient had severe fatigue, one had severe dizziness, and one patient's surgical procedure was changed. The median plasma levels of gabapentin were 34 mu mol/mL (range, 23-51 mu mol/mL) in 34 patients. In Group P, one patient withdrew from the study preoperatively and one developed transient neurological symptoms postoperatively. The demographic data and mean duration of anesthesia and surgery were similar in both the groups. The total propofol and remifentanil consumption in Group G (1847 +/- 548 mg/3034 +/- 1334 mu g) was significantly less than that of Group P (2293 +/- 580 mg/4287 +/- 1282 mu g) (P = 0.01). However, tracheal extubation could be done earlier in Group P (4.5 +/- 2 min) than in Group G (16.6 +/- 22 min) (P < 0.001). Pain scores were significantly higher in Group P at 15 min, 30 min, and 1 h (P < 0.001). The total morphine consumption was also significantly higher in Group P (33 +/- 17 mg vs 24 +/- 19 mg) (P = 0.01). The postoperative sedation scores were significantly higher in Group G at 15 min, 30 min, 1 h, and 2 h (P < 0.001). CONCLUSIONS: The administration of gabapentin to patients undergoing craniotomy for supratentorial tumor resection was effective for acute postoperative pain. It also decreased analgesic consumption after surgery. However, it may lead to side effects such as delayed tracheal extubation and increased sedation postoperatively. (Anesth Analg 2009;109:1625-31)