Comparative Ecotoxicological Assessment of Acetaminophen and Diclofenac using Freshwater African Catfish Clarias gariepinus (Burchell 1822)

The use and abuse of analgesics, commonly referred to as painkillers is on the rise globally. This study examined the acute toxicity and sub-lethal effects on liver function (ALT, AST, ALP) and anti-oxidative stress enzymes of the African Catfish, Clarias gariepinus, exposed to two analgesics, acetaminophen and diclofenac. The fingerlings (4 weeks old), were exposed to high concentrations of both analgesics to determine their acute toxicity of a 96 h period. The results indicated that diclofenac was approximately 500 times more toxic to the catfishes with a 96 h LC50 of 2.6 mg/L compared to 1283.6 mg/L in those exposed to acetaminophen. Another batch of the catfishes was subsequently exposed to two sub-lethal concentrations (1/10th 96 h LC50 and 1/100th 96 h LC50) of both compounds for 28 days. The result of the sub-lethal assessment indicated that the responses were not always dose-dependent. The liver function enzyme assessments indicated a varied result with AST values slightly lower than control while ALP values were all higher in the exposed groups than the control. Only catfishes exposed to 1/10th 96h LC50 diclofenac showed significant inhibition (P<0.05) of ALT enzyme activities compared to control. The activities of the anti-oxidative stress enzyme catalase were lower in those exposed to acetaminophen compared to control and this was also the case for glutathione-S- transferase (GST) activities for exposures to both concentrations of both analgesics. The findings point to the need for the inclusion of pharmaceuticals in our national effluent quality standards so as to mitigate potential harm to aquatic life. Keywords: Acetaminophen, diclofenac, toxicity, catfish