Abstract A number of isosteres (oxadiazoles, thiadiazoles, tetrazoles and diazines) of benzocaine were prepared and evaluated for their capacity to induce methemoglobinemia— with a view to their possible application as humane pest control agents. It was found that an optimal lipophilicity for the formation of methemoglobin (metHb) in vitro existed within each series, with 1, 2, 4-oxadiazole 3 (metHb%= 61.0±3.6) and 1, 3, 4-oxadiazole 10 (metHb% ...