A comparative study of efficacy and safety of gabapentin versus amitriptyline as coanalgesics in patients receiving opioid analgesics for neuropathic pain in malignancy

Objective: To assess the efficacy and safety of gabapentin and amitriptyline along with opioids in patients suffering from neuropathic pain in malignancy. Materials and Methods: Eighty-eight adult patients between 18 and 70 years of age with neuropathic pain in stage III malignant disease, matched for baseline charactistics, were randomly assigned to two groups. Group A received oral tramadol and gabapentin and group B received oral tramadol and amitriptyline. The treatment duration of each patient was 6 months. Visual analog scale (VAS) was the primary efficacy parameter. Verbal rating scale (VRS) score, percentage of pain relief (PPR), and global pain score (GPS) were the secondary efficacy parameters. Oral morphine tablets or fentanyl transdermal patch were used as rescue medication. Data analysis was carried out in Graph Pad instat. Results: There was decline in VAS pain score from baseline in both the groups in the early phase of the study though there was no statistically detectable difference between them at any study point. Similar changes were seen in the secondary efficacy parameters too. Thus both the drugs were effective in providing relief to cancer patients with neuropathic pain though there was no statistically detectable difference in efficacy between them. Six patients in group A and eight patients in group B required rescue medication. A total of 12 subjects in the gabapentin group and 15 subjects in the amitriptyline group experienced adverse events which were of mild to moderate grades. Conclusions: Amitriptyline may be a suitable alternative for management of neuropathic pain in cancer patients although gabapentin is widely used for this purpose. The lower cost of amitriptyline may favor patient compliance with lesser number of drop-outs.