Chapter 4 : Pharmacodynamics Flashcards
what is the therapeutic index?
-identifies safety index
-ratio between median lethal dose to median effective dose
-the higher the value, the safer the drug
-to monitor for the therapeutic index, you need to monitor serum blood level (gentamicin, tobramycin, vancomycin, lithium, digoxin)
-used for individual monitoring, really important for narrow therapeutic range
what is margin of safety?
-amount of the drug that is lethal to 1% of the animals divided by the amount that produces 99% of therapeutic effects
-prescription drug has to have a high MOS to be reclassified as OTC
-more precise, and focuses on the dose that would cause the least harm
-not used on an individiual level like TI, used for population level assessments
what are the three phases of dose-response relationship?
-phase 1: lowest dose (subtherapeutic)
-phase 2: most desirable range
-phase 3: plateau
-once phase 3 has been reached, increasing the dose will not increase theurapetic effect, it may even cause toxicity, for ex. antibiotics
what is potency vs efficacy?
-potency: amount of drug needed to produce a specific effect (lower dose, but strong effect= high potency)
-efficacy: greatest maximal reponse produced by drug
-efficacy is more important in terms of pharmacotherapeutic effects
what does a high intrinsic activity mean?
-the drug binds to the receptor and produces a strong effect
-antagonist do not have instrinic activity, because they don’t produce an effect themselves, they just block the receptor site preventing the agonist from binding to them
what do most drugs do with a physiological process?
enhance or inhibit
what are partial agonist?
-produce a lesser endogenous effect
-not recommended to treat chronic pain, as these drugs have a ceiling effect, therefore if the pain increases too much, these drugs might not be able to treat it
what is additive effect?
-two drugs of similar effects are taken together
-1+1=2 (diuretic + beta blocker = decreased blood pressure)
