Objective:To evaluate carbamezapine (CBZ) for neuritic pain relief in Guillain-Barré syndrome (GBS) patients in the intensive care unit (ICU).Design:Prospective, double-blind, randomly allocated crossover study days.Setting:ICU in a tertiary care university hospital.Participants:Twelve consecutive, conscious adult (22-54 yrs) patients with GBS during recovery from the muscular weakness and receiving pressure-support ventilation in the ICU. All patients complained of severe backache and/or leg cramps and tenderness in muscles, and they required opioids for pain relief.Interventions:CBZ (100 mg every 8 hrs) or equivalent placebo was given to nursing staff in coded powder form. Medication was given to patients through a nasogastric feeding tube. The same coded medicine was given for 3 days, and after a 1-day omission, a second set of coded powder was given for the next 3 days in a randomized, double-blind, crossover fashion. Pethidine (1 mg·kg−1) was given intravenously in between, if the pain score was >2. Group 1 (n = 6) patients were given a placebo on the first 3 days, followed by CBZ. Group 2 (n = 6) patients were given CBZ on the first 3 days, followed by a placebo.Measurements and Main Results:In these two study periods of different medications, we observed and scored pain (1, no pain; 5, severe pain), sedation (1, alert; 6, asleep, does not respond to verbal command), and total pethidine requirement per day. In group 1 patients, a significant (p< .001) improvement in the sedation score and a low requirement for pethidine was observed 3 days later, when CBZ was started. However, in group 2 patients, a gradual increase in the pethidine requirement and a high sedation score were noteworthy in the later days of placebo medication. Observations were also analyzed for CBZ days vs. placebo days. Overall, the pain score (1.7 ± 0.8) during the CBZ period of both regimens was significantly (p< .001) lower than during the placebo days (3.1 ± 0.9). Significantly higher doses of pethidine (3.7 ± 0.9 mg/kg/day) were used on the placebo days than on the CBZ days (1.7 ± 1.0 mg/kg/day).Conclusion:The pain in GBS has a dual origin, and we recommend CBZ as an adjuvant to treat pain in GBS patients, during the recovery phase in the ICU, to reduce the narcotic requirement.