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Pharmacology Ch 5
Pharmacology
| Question | Answer |
|---|---|
| Pharmacodynamics | The study of the biochemical & physiologic effects of drugs & the molecular mechanisms by which those effects are produced (what drugs do to the body & how they do it) |
| Dose-Response Relationship | Relationship between the size of an administered dose & the intensity of the response produced - usually graded (gets more intense with higher dose) |
| Dose-Response Relationship Determines | 1) Maximum amount of drug we can use 2) Maximum response a drug can elicit 3) How much we need to increase the dosage to produce the desired increase in response |
| Maximal Efficacy | The largest effect that a drug can produce - match the intensity of the response with the patient's need (e.g. don't give morphine for a headache) |
| Relative Potency | The amount of drug we must give to elicit an effect - a potent drug produces its effects at low doses (potency isn't that important) |
| Drugs | Chemicals that produce effects by interacting with other chemicals - drugs cannot give cells new functions |
| Receptor | Any functional macromolecule in a cell to which a drug binds to produce its effects |
| Drug-Receptor Interactions | 1) Always reversible 2) Receptor activity regulated by endogenous compounds 3) Drug binding either mimics or blocks action of endogenous molecules (doesn't create new actions) |
| 4 Primary Receptor Families | 1) Cell Membrane-Embedded Enzymes 2) Ligand-gated Ion Channels 3) G protein-Coupled Receptor Systems 4) Transcription Factors |
| Cell Membrane-Embedded Enzymes | Immediate response - receptor spans membrane - binding of drug causes increased catalytic activity on other side of membrane |
| Ligand-Gated Ion Channels | Immediate response - receptor spans membrane - binding of drug opens channel so specific ions can go through (direction depends on [ion]) |
| G Protein-Coupled Receptor Systems | Immediate response - R + GTP + Effector - serpentine structure that spans cell membrane 7 times |
| Transcription Factors | Delayed response - located on DNA in cell nucleus - stimulate transcription of mRNA to make protein - only activated by lipid soluble ligands |
| Selectivity | If a drug interacts with only one type of receptor, & if that receptor type regulates just a few processes, then the effects of the drug will be relatively selective - the more selective a drug, the fewer SE's it will have |
| Simple Occupancy Theory | Intensity of response to a drug is proportional to the number of receptors occupied |
| Modified Occupancy Theory | Incorporates affinity & intrinsic activity into the equation |
| Affinity | Strength of the attraction of the drug to its receptor (reflected in its potency) |
| Intrinsic Activity | Ability of the drug to activate a receptor upon binding - drugs with high intrinsic activity cause intense receptor activation (have high maximal efficacy) |
| Agonists | Molecules that activate receptors - have both high affinity & high intrinsic activity - can make processes go faster or slower |
| Antagonists | Drugs that prevent receptor activation - have affinity, but no intrinsic activity - have virtually no effects of their own on receptor function |
| 2 Types of Antagonists | 1) Noncompetitive 2) Competitive (most of them) |
| Noncompetitive Antagonists | Bind irreversibly - impact not permanent (until cell dies & replaced by new one) |
| Competitive Antagonists | Compete with agonists for receptor binding - reversible - equal affinity (whichever has highest concentration) |
| Partial Agonists | Have only moderate intrinsic activity - maximal effect can produce less than that of a full agonist - can act as antagonists as well |
| Regulation of Receptor Sensitivity | Continuouse exposure to agonists can -> receptor desensitization (downregulation). Continuouse exposure to antagonists can -> hypersensitivity. |
| Drug Responses That Do Not Involve Receptors | Simple physical or chemical interactions with other small molecules - examples of receptorless drugs: antacids, antiseptics, saline laxitives, chelating agents |
| ED50 | The dose required to produce a defined therapeutic response in 50% of the population (Average effective dose) |
| Interpatient Variability in Drug Responses | The initial dose is just an approximation. Subsequent doses must be "fine tuned" based on patient's response. |
| LD50 | Average Lethal Dose |
| Therapeutic Index | LD50:ED50 - measure of a drug's safety - the higher the therapeutic index, the safer the drug |
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