Evidence-based veterinary medicine (EBVM) is a formal approach to integrating the best research evidence with clinical expertise and client perspectives to provide high-quality veterinary services. This chapter will focus on the application of EBVM principles to pharmacotherapy (the selection of pharmacological treatments and dosage regimens). The EBVM approach guides the busy practitioner through the massive amount of constantly and rapidly evolving scientific data, so that he/she can make the best clinical decisions possible by focusing on information that is directly related to specific patient problems (Cockcroft and Holmes, 2003).

It seems obvious that treatment choices should be based on the best available evidence, but many approaches to clinical practice can result in biased or incomplete assessment of available options. These approaches include, but are not limited to, relying on standardized protocols, perusing the information about drugs that is provided by pharmaceutical companies, basing decisions on pathophysiological rationale or unsystematic clinical observations of previous cases, seeking advice from colleagues and experts, and performing unstructured appraisals of information in textbooks, journals, and online resources. Personal experience is subjective and can be misleading, predictions based on pathophysiological rationale need to be validated with randomized controlled clinical trials, and evidence from the scientific literature needs to be systematically evaluated to identify poorly designed studies, poor-quality data, or biased analyses.

EBVM sets itself apart from other approaches to clinical practice in that it emphasizes the systematic review of all available evidence. Randomized controlled clinical trials reported in the scientific literature are the preferred evidence, but, if these do not exist, evidence from expert opinion, case reports, personal experience, and other nonliterature-based sources can be considered. Regardless of the source, all evidence needs to be collated, assessed, and ranked to support objective decisions regarding the treatment of patients.

EBVM can be defined as “the conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients” (Sackett et al., 2000). This means that clinicians should follow an explicit and methodical approach to their clinical decision making so that they can explain how and why one treatment option was chosen over another. There are three foundational skills that are required to do this:

1. Be able to identify information needs and transform them into questions.
   
2. Know where to seek the evidence needed to answer these questions.
   
3. Be able to understand and critically appraise (judge the quality) all the evidence.