Appropriate Versus Inappropriate Antimicrobial Therapy

Patricia M. Dowling, DVM, MSc, Diplomate ACVIM & ACVCP


• Successful antimicrobial therapy relies on administering sufficient doses so that pathogens at the site of infection are killed or sufficiently suppressed and can be eliminated by the host's immune system.
• Pharmacokinetics (PK) is what the body does to a drug. It is the mathematical description of absorption, distribution to the various tissues, metabolism of lipid-soluble drugs into water-soluble metabolites, and finally renal excretion.
• Pharmacodynamics (PD) is what the antimicrobial agent does to the bacteria. It describes the drug action and responses of the bacteria.
• Pharmacokinetics and pharmacodynamics are interrelated-PK determines the amount of drug that reaches the site of action, and the intensity of a PD effect is associated with the drug concentration at the site of action.
• Benefits of the PK/PD approach include increased efficacy of antimicrobial therapy and minimized antimicrobial resistance.

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