Piperonyl butoxide is used as a potentiator or synergist in many pesticide formulations, including carbamates, organophosphates, organochlorines, pyrethrins, pyrethroids, and d-limonene. It decreases breakdown of these pesticides in the animal or insect’s body by inhibiting mixed function oxidase enzymes and makes the pesticide more toxic to the insect—and the host. Animals that are debilitated or have decreased drug-metabolizing capability become more susceptible to the pesticide. However, toxins that must be activated in the body to a toxic form are frequently less toxic when piperonyl butoxide exposure occurs at the same time. This potentiating or synergistic effect has been seen in many species, including cats, dogs, rats, and people. Cimetidine, a drug that reduces stomach acid secretion by blocking gastric H2 receptors, and the antibiotic chloramphenicol have the same effect.