Wepfer made important contributions in the fields of experimental pharmacology and toxicology. He conducted experiments on the toxicity of water hemlock, hellebore, monkshood,[1] and warned against the usage of arsenic, antimony, and mercury in medicine. In the fields of pharmacology/toxicology he published an influential work on water and poison hemlock called Cicutae aquaticae historia et noxae (1679).[2]