Co-administration of Ondansetron with Tramadol Decreases efficacy of Tramadol in Intensive Care unit patients

Abstract

Background: Tramadol is routinely used analgesic postoperatively in ICU patients, it is known to cause nausea and vomiting. Pharmacologically it has analgesic action, centrally as it blocks the reuptake of serotonin at spinal pathway. Ondansetron is a serotonin receptor antagonist used in postoperative time, cancer chemotherapy, radiation therapy, as an anti-emetic. In-spite of known pharmacological antagonism centrally, these two drugs are routinely used together postoperatively. The purpose of this study was to assess tramadol's analgesic efficacy when given alone versus when given along with ondansetron. Requirement of rescue analgesic and side effects like sedation, nausea and vomiting amongst two groups were also evaluated. Methods: This prospective randomized study was conducted at surgical ICU enrolling 60 patients. We have separated patients into two groups of 30 each. Group A was given 100milligram of injection tramadol intravenously slowly over ten minutes and after 12mg/hour tramadol plus ondansetron in the dose of 0.8mg/hour. Group B was given 100milligram of injection tramadol slowly over ten minutes followed by infusion of tramadol 12mg/hour. In both A and B groups, hemodynamic parameters were evaluated at 0, 3, 6, 12, and 24 hours along with pain assessment using the Visual Analog Scale (VAS) in the range of 0 to 10. Rescue analgesia was administered in the form of paracetamol 1 gram IV at any time if VAS > 4. A four point ordinal scale was used to measure side effects such as nausea, vomiting, and the degree of sedation. Results: In group A, postoperative VAS scores were higher up to 24 hours compared to group B, suggesting greater analgesia in the tramadol infusion group only. There was a significant difference when both the groups were compared with respect to requirement of rescue analgesia with 4 patients in group A and no patient in group B requiring rescue analgesia. No significant difference was found with respect to nausea and vomiting and the degree of sedation in both classes. Conclusion: In ICU patients administration of tramadol along with ondansetron should not be practiced as ondansetron decreases the analgesic efficacy of tramadol.