Therapeutic decision making
- Often a difficult and complex process
- Often confusing and contradictory information (researchers, horse owners, websites & list serve's)
- Frequently our decisions are based on:
- Our last successful case
- Our last failure
- Our last case
- Mechanism of action
- Route of delivery
- Metabolism/ elimination
- Potential for toxicity
A Historical Perspective
- An ancient peasants house burned down. In it was his pig. When the peasant became hungry enough he tasted the cooked pig
and reported its flavor to be miraculous.
- Thereafter, when the villagers wanted to eat roast pig they put one in a house and burned it down.
What the body does to the drug
Describes the movement of drugs in the body
Clinical pharmacokinetics is important for formulating dosage regimens in animals with disease
What the drug does to the body
Describes the action of the drug on the body- typically related to:
- Plasma/serum concentrations (window into the body)
- Exceptions: Macrolides for respiratory disease & other compounds that are 'tissue-loving'
Values poorly defined in horses- we extrapolate desired 'dose' from human or small animal lit.
Drug concentration in the blood stream usually proportional to drug concentration at site of action
Identify the agent
1. Gram stain (+) (-)
2. disk diffusion test; susceptible, intermediate, resistant. (based on human serum concentrations)
3. MIC - more expensive but more info. resistance often a concentration phenom. (minimum concentration of an AB that inhibits
growth of a pathogen in vitro)
Kirby-Bauer susceptibility test
Inexpensive & considerable experience in vet.med.
Disadvantage- difficult to standardize, information on relative susceptibility hard to interpret (accurate??) and temptation
to choose drug with largest zone (appropriate?)