The Role of Adrenaline, Noradrenaline, and Cortisol in the Pathogenesis of the Analgesic Potency, Duration, and Neurotoxic Effect of Meperidine

Background and Objectives: The purpose of the study was to investigate the role of adrenaline (ADR), noradrenaline (NDR), and cortisol in the pathogenesis of the analgesic potency, duration, and epilepsy-like toxic effect of meperidine. Materials and Methods: The experimental animals were separated into 11 groups of six rats. In the meperidine (MPD) and metyrosine + meperidine (MMPD) groups, paw pain thresholds were measured before and after the treatment between the first and sixth hours (one hour apart). In addition, ADR and NDR analyses were performed before and after the treatment, between the first and fourth hours (one hour apart). For the epilepsy experiment, caffeine, caffeine + meperidine, and caffeine + meperidine + metyrapone groups were created, and the treatment was applied for 1 day or 7 days. Groups were created in which caffeine was used at both 150 mg/kg and 300 mg/kg. Epileptic seizures were observed in epilepsy groups, latent periods were determined, and serum cortisol levels were measured. Results: In the MPD group, pain thresholds increased only at the first and second hours compared to pre-treatment, while ADR increased at the third hour, leading to a decrease in pain thresholds. In the MMPD group, the increase in paw pain thresholds at 1 and 6 h was accompanied by a decrease in ADR and NDR. In the caffeine (150 mg/kg) + meperidine group, 1-day treatment did not cause epileptic seizures, while seizures were observed and cortisol levels increased in the group in which treatment continued for 7 days. When cortisol levels were compared between the group in which caffeine (300 mg/kg) + meperidine + metyrapone was used for 7 days and the animals receiving caffeine (300 mg/kg) + metyrapone for 7 days, it was found that cortisol levels decreased and the latent period decreased. Conclusions: The current study showed that if serum ADR and cortisol levels are kept at normal levels, a longer-lasting and stronger analgesic effect can be achieved with meperidine, and epileptic seizures can be prevented. © 2023 by the authors.