Week 3: Time Course of Drug responses + half life Flashcards
What are the 3 time courses for a drug response?
- Plasma Concentration
- Onset of action
- Duration
Why does plasma concentration affect drug response? (2)
- minimum effective concentration and maximum effective concentration, AKA THERAPEUTIC RANGE
- in order for the drug to be effective, you must have a minimum concentration in the blood
What is a drug’s half life (t1/2)?
The time required for the amount of drug in the body to decreased by 50% (plasma concentration)
what does half life determined?
- dosing intervals (how often drug needs to be given)
ex. if t1/2 is 12 hours, the medication is given every 12 hours to keep the plasma levels in therapeutic range
What is acetaminophen’s half life?
- 4 hours
If someone takes more of a drug, does that mean their half life will be longer?
no, half life stays the same
What does half life help predict? Why? (2)
- when the therapeutic level will be reached
- it takes 4 half lives to reach steady therapeutic range in the plasma
If loading doses allow a faster drug plasma concentration in the therapeutic range, why don’t we give loading doses for all medications?
- even though loading doses get the patient to the therapeutic range faster, it can be dangerous even if the drug kicks in fast
- done in urgent situations
How many half lives does it take for a drug to be eliminated from the body?
4 half lives
What is pharmacodynamics?
The study of biochemical and physiological effects of drugs on the body and the molecular mechanism by which of those effects are produced
What are the 6 factors of pharmacodynamics?
- efficacy
- potency
- dose
- relationship
- therapeutic index
- response
Please explain the graph on dose response relationships as shown.
What is the ceiling effect? (2)
- after a certain amount of doses, the drug is no longer effective
- just side effects
