Effects of temperature on the elimination of benzocaine and acetylated benzocaine residues from the edible fillet of rainbow trout (Oncorhynchus mykiss)

The effect of temperature (7 degrees C and 16 degrees C) on the extent of a ccumulation and the elimination of benzocaine (BNZ) and its metabolite, ace tylated benzocaine (AcBNZ), in the fillet tissue of rainbow trout was inves tigated Residues were measured after bath exposure to an anesthetizing conc entration of benzocaine (30 mg/l for 5 min) followed by a maintenance conce ntration (15 mg/l for 30 min). Immediately after exposure, the BNZ concentr ation in fillet tissue was approximately 27 mu g/g at both temperatures; Ac BNZ was 0.3 mu g/g at 7 degrees C and 0.6 mu g/g at 16 degrees C. The rates for elimination (alpha and beta) of BNZ and AcBNZ were not significantly d ifferent between the two temperatures. Terminal half-lives of elimination f or BNZ were 1.62 h at 7 degrees C and 1.63 h at 16 degrees C; half-lives fo r AcBNZ were 2.36 h at 7 degrees C and 2.77 h at 16 degrees C.