1 - Applied PK-PD Flashcards
What is the difference between individual PK and population PK?
- Individual = intensive sampling from few px
- Population = sparse sampling from more px
What needs to be considered when choosing an antimicrobial?
- Pathogen
- Mechanism of action
- Degree of susceptibility
- Cidal vs static
- Combination therapy
- Severity of illness
- Site of infection
- Immune status
Define pharmacodynamics
Relationship between drug concentration profile and response/efficacy
Dosing is based on maximizing ____
Cmax
What would be the benefit to a prolonged infusion and when would you want to use this?
- So that Cmin doesn’t fall below therapeutic window
- Used for drugs w/ short t1/2
Define toxicodynamics
Relationship between drug concentration profile and adverse effects or toxicity
___ is often more important w/ respect to toxicity
Cmin
You can consider that steady state has been reached after ____ half lives
4-5
What can cause increased Vd?
- Pregnancy
- Cystic fibrosis
- Severe liver dysfunction
- Neonates
- Obesity
- Burn patients
What is the relationship between fe (fraction unchanged in urine), Clcr, and half life?
- For a drug w/ a high fe (ex: 90%), changes in Clcr will have a dramatic effect on t1/2 (lower Clcr will prolong t1/2)
- For a drug w/ low fe (ex: 10%), changes in Clcr won’t effect t1/2 b/c the drug isn’t heavily excreted by the kidneys
How do you calculate ke?
[ ln (measured peak) - ln (measured trough)] / change in time
What happens if an early peak sample is used to calculate ke?
Will cause the half life to be depicted as faster than it actually is
What is Vd used to show?
- How much drug is left in the blood after administration
- High Vd means drug has gone to other parts of body besides blood
What can cause Vd to decrease?
Dehydration
What is the formula for Vd? What must be included in this formula?
Vd = D / (Cmax - Cmin)
- Must have Cmax and Cmin, can’t use measured peak and trough
