LEC 24 Clinical Pharmacokinetics II Flashcards
What is clearance?
- a measure of the efficiency of drug removal from an eliminating organ
- The volume of blood that must be acted on per unit of time to account for the rate of elimination by all organs (liver, kidney, etc)
How do you calculate systemic clearance (Cls)?
How do you calculate renal clearance (Clr)?
fraction of the dose excreted times Cls
How does enzyme induction affect Cls?
- Increases Cls
- Enzyme inducing drugs increase the metabolism of all drugs
Why is the first pass effect important?
- affects the bioavailability (F)
- decreases the amount of drug in systemic circulation
- alters pharmacological effects of drug
What is bioavailability (F)?
the fraction of a dose absorbed intact into the body
How do you calculate bioavailability (F)?
If the bioavailability of a drug is closer to 100%, what does this indicate?
The drug can be switched from IV to PO with minimal dosing adjustments
What does tau (τ) represent in chronic dosing?
the dosing interval
What does Css(oral) represent in chronic dosing?
the average steady state concentration for chronic dosing
Why is drug-protein binding important to consider?
- Only unbound/free drug distributes out of the blood to the tissues
- Sites of drug action are extravascular
What is the equation for maintenance dosing?
What is the equation for a loading dose?
What is the equation for the steady state concentration for an infusion?
