Morphometric, hematological and oxidative stress changes in Clarias gariepinus following sub-chronic exposure to tramadol

Tramadol is among the most famous analgesic drugs used for the management, treatment and relief of moderate to severe pain conditions. The present study investigated the effects of tramadol on the behavior, mortality, morphometric, hematology and oxidative stress parameters of C. gariepinus juveniles. The 96 h LC50 value of tramadol determined by probit analysis was 88.76 mg/L. Based on this value, fish were exposed to sublethal concentrations of 4.44, 8.88, 17.75 mg/L tramadol and 0.0 mg/L (control) for the period of 15 days and allowed to recover for 5 days. Fish exposed to tramadol showed some abnormal behavioral responses and mortality increased with increase in the exposure duration and concentrations except for the control. There were variations in hepatosomatic index (HSI) and condition factor (CF) in fish exposed to tramadol. Exposure of C. gariepinus to tramadol elicited reduction in the values of white blood cell (WBC), red blood cell (RBC), hemoglobin (Hb), packed cell volume (PCV) and mean corpuscular volume (MCV) while the values of mean corpuscular hemoglobin (MCH) and the mean corpuscular hemoglobin concentration (MCHC) increased. The values of catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR), reduced glutathione (GSH) and lipid peroxidation (LPO) increased significantly in the exposed fish compared with the control. The values of glutathione peroxidase (GPx) however decreased. The results of the present study demonstrate that tramadol is toxic to fish and its use should be monitored in the aquatic environment. [Display omitted] •Tramadol is toxic and alters the behavior of Clarias gariepinus juvenile•Hepatosomatic index and condition factor in C. gariepinus were elevated after exposure to tramadol•Exposure of C. gariepinus to tramadol elicited mixed trends in the blood parameters.•The drug induced oxidative stress in the gill tissues of the exposed fish.•Our study indicate that tramadol is toxic to fish and must be regulated to avoid toxic effects on non-target aquatic species especially fish