The research activities of Erspamer spanned more than 60 years and resulted in the isolation, identification, synthesis and pharmacological study of more than sixty new chemical compounds. Among these compounds were polypeptides and biogenic amines, and also some alkaloids. Most of these compounds were isolated from animals, predominantly amphibians.
In the late fifties, his research shifted to peptides. In the laboratories of the Institute of Medical Pharmacology, University of Rome, he isolated from amphibians and mollusks more than fifty new bioactive peptides. These became the subjects of numerous studies in other laboratories in Europe and North America. In 1979, he focused on opioid peptides specific to Phyllomedusa tree frog from Central and South America. These were used by the native Indians in initiation rites, to increase their prowess as “hunters” and make them feel “invincible”. They applied secretions from the skin of these frogs that resulted in analgesic effects.