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NURS 572A
Chapter 5 Pharmacodynamics
| Question | Answer |
|---|---|
| pharmacodynamics definition | what the drug does to the body. biochemical and physiologic effects of a drug and the molecular mechanism by which they are produced |
| dose-response relationship definition | intensity of response of a drug at various dosages |
| what dose dose-response relationship determine | minimum/maximum response that can be expected |
| dose response shown best on what type of curve | logarithmic |
| 3 phases of dose-response show what? | *Phase 1 - dose to low to elicit response *Phase 2 - graded response (dose inc, effect inc) *Phase 3 - inc dose doesn't inc effect (plateau) |
| Maximal efficacy | largest effect drug can produce |
| relative potency definition | amount of drug that is needed to elicit a specific response |
| Does relative potency imply anything about efficacy? | no. a potent drug produces effects at low doses. about dose/effect relationship |
| When is relative potency important? | if the side effects have the same relative ratio as efficacy (smaller dose of more potent drug can be given to elicit same response, yet cause fewer side effects) |
| Binding of drug to receptor is generally | reversible (desired) |
| 4 types of receptors (CLGT) | *cell membrane embedded enzymes (seconds) *ligand-gated ion channels (extremely fast) *G-protein couple receptor (fast) *Transcription factors (slow) |
| Example of cell membrane embedded receptor | insulin |
| example of Ligand-gate ion channel receptor | ACh, GABA |
| example of G-protein receptor | NE, Ser, Histamine, peptide hormones |
| example of transcription factor receptor | thyroid, steroid hormones |
| receptor definition | normal point of physiological control, regulated by molecules supplied to the body |
| receptor action | can mimic or block when bound by drugs |
| can drugs give new functions to cells? | no, only alter the rate of pre-exisiting processes (except gene therapy) |
| properties of ideal drug | effective, safe, selective |
| high receptor selectivity produces | intended effect with little side effect |
| does selectivity guarantee safety? | no - though we chemically modify to increase selectivity |
| single occupancy theory | intensity of response related to number of receptors occupied but doesn't address max response or diff in potency |
| modified occupancy theory | response considers affinity and intrinsic activity |
| affinity | strength of attraction between drug/receptor (potency) |
| Intrinsic ability | ability to elicit response once drug/receptor bound (maximal efficacy) |
| agonist drug functions (3) | *activate receptor (flip on switch) *mimic activity of endogenous transmitter *have high affinity AND high intrinsic activity |
| Effect of agonist drug | can either increase or decrease activity of physiological process |
| example of agonist dobutamine | Activate NE receptors in heart --> increase HR |
| Example of cholinergic agonist bethanechol | mimics ACh at muscarinic sites in heart --> decrease HR |
| antagonist drug definition | block receptor, prevent its activation |
| What must be present for antagonist drug to exert its effect? | agonist must be present (system 'on') for antagonist to exert effect (turn 'off') |
| can antagonist produce unwanted effects in absence of agonist? give example | yes. antihistamine can prevent runny nose unless histamine has already occupied receptor.Even so, antihistamine can cause sedation |
| Antagonist drug classifications | *non-competitive (bind IRreversibly/insurmountable) *competitive (bind reversibly/surmountable) |
| Noncompetitive antagonist effect | reduces maximal response/efficacy (reduces number of available receptors) |
| Competitive antagonist effect | decrease potency - whichever (agonist, antagonist) is in higher concentration 'wins' |
| partial agonist | mixed action, acting as agonist when binds, competitive inhibitor(antagonist) to other drug |
| Pentazocine example of partial agonist MOA | agonist when alone, when administered with morphine, blocks receptors that morphine needs |
| receptor sensitivity - continuous agonist | causes desensitization by down-regulation of either # of receptors or their sensitivity |
| receptor sensitivity - continuous antagonist | causes hypersensitivity or up-regulation, bwo synthesis of more receptors |
| tolerance definition | higher dose needed to reach same effect |
| interpatient drug response variability | measurement of variability between population to define objective endpoint bwo frequency distribution curve |
| ED50 | dose that elicits expected response in 50% of patients (average effective/standard dose) |
| LD50 | lethal dose in 50% of population |
| clinical implications of variability(3 bears!) | *too low - not effective *too high - effected with unwawnted side effects *just right - good effect with no/tolerable incidence of side effects |
| therapeutic index | ration of LD50/ED50 determines safety of drug. the higher the number, the safer the drug |
Created by:
lorrelaws
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