Perspectives in Veterinary Pharmacology and Toxicology

Veterinary pharmacology and toxicology are being increasingly recognized as important disciplines and were also rapidly changing and evolving in the mid-twentieth century. By the mid-1950s, phar-macology and toxicology were a highly active area of veterinary medicine; veterinary pharmacology and toxicology emerged as new disciplines, closely related, because they were involved in developing new compound, particularly new antimicrobials and antiparasitics to control infection diseases, and analgesic/non-steroidal anti-inflammatory drugs affecting different animal species. The research and development cost of new antimicrobials that must fulfill the new regulatory requirements is considered high; in drug development projects, toxicology closely linked with pharmacology and pharmacokinetics is decisive in the success or failure of a new drug candidate. During the last years, the following new antimicrobial active substances have been authorized for use in veterinary medicine: difloxacin (belonging to the class fluoroquinolones, authorized in 1998 after marketing of enrofloxacin in 1987), valnemulin (a pleuromutilin, 1999), pirlimycin (a lincosamide, 2001), tulathromycin (a macrolide, 2003), tylvalosin (a macrolide, 2004), ceftiofur (a third-generation cephalosporin, 2005), cefovecin (a third-generation cephalosporin, 2006), gamithromycin (a mac-rolide, 2008), pradofloxacin (a fluoroquinolone, 2011), and tildipirosin (a macrolide, 2011). None of these antimicrobials belongs to a new class of antimicrobials. It is known that most veterinary drugs derive from either the human pharmaceutical industry (antibiotics, analgesic, antiobesity, anticancer, cardiovascular) or the plant protection products (insecticides, parasiticides). Like veterinary medicine, veterinary pharmacology and toxicology is not an easy matter because of multiplicity of animal species as well as breed, age, sex, and (patho)physiological status concerned that may respond differently to certain drugs, food, feed, pesticides, and industrial products as well as contaminants or toxins. The inter-and intraspecies differences as well the variability within and across animal populations are the essence of veterinary pharmacology and toxicology. It is know the species differences in the metabolism and excretory processes of different chemical compounds. In the 60s of the twentieth century, the extrapolation dose regimens from one species to another was a common practice; however, nowadays it is known that pharmacokinetics/toxicokinetics (PK/PD) differences remain for drugs, pesticides, contaminants, or toxins that is the cornerstone of veterinary pharmacology and toxicology. Moreover, the analytical techniques to measure plasma/ tissue concentrations of xenobiotics are changed and the sensibility been improved. Analytical methods whether intended for use in pharmacokinetic (PK) and metabolism studies, residue depletion studies, or regulatory control programs for residues of veterinary drugs and pesticides, and contaminants, share a common subset …