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Principles of Pharm
Principles of Pharmacokinetics & Pharmacodynamic
| Question | Answer |
|---|---|
| Potency | The measure of the amount of drug (dose,mg) required to produce a given degree of effect. (Rarely of clinical importance) |
| Efficacy | The ability of a drug to produce a desired therapeutic effect. |
| Affinity | Measure of the strength of attraction between a drug and its receptor. Describe the tightness of the bond. |
| Selectivity | Refers to the degree to which a drug acts upon one site relative to all possible sites. Usually the more selective a drug is, the fewer adverse effects it will cause. |
| Protein binding | some drugs are bound to plasma proteins, mostly albumin. Drugs bound to these proteins are pharmacologically inactive while bound. |
| First-pass Metabolism | Drugs absorbed in the small intestine are first exposed to the liver and may be extensively metabolized before reaching systemic circulation |
| Prodrug | Inactive compound that must be metabolized in order for it to become active |
| Chelation | Chemical bonding that prevents absorption |
| Enzyme Induction | (rev up) Increases metabolism = lower drug levels = loss of efficacy (lower blood levels) |
| Enzyme Inhibition | Decrease metabolism = higher levels of blood = increased effects, adverse effects, & toxicity |
| Volume of Distribution (Vd) | mathematical concept describing the amount of drug in the body in relation to the concentration of drug in the plasma |
| List the FDA Pregnancy Categories | A,B,C,D,X |
| Category A | Human studies show no fetal risk |
| Category B | Animal studies show no fetal risk; probably safe in humans |
| Category C | Either animal studies do show fetal effects or no studies exist, Drug should only be given if the potential benefits justify the potential risk. |
| Category D | Evidence of human fetal harm exists |
| Category X | Contraindicated! Risk to fetus clearly outweighs any possible benefit |
| Absorption | movement of drug from its site of administration into the bloodstream |
| Distribution | movement of drug into the various body fluids & tissue |
| Metabolism | biotransformation-chemical alteration of the parent compound usually resulting in enhanced excretion, inactivation, or sometimes active metabolites |
| Excretion | process by which the drug is eliminated from the body. Some drugs are excreted after metabolism. Som drugs are excreted "unchanged" |
| half-life | time required for the drug's plasma concentration to be reduced by one-half |
| Bioavailability | fraction (%) of drug available in bloodstream after administration as compared to the IV route |
| Therapeutic Index | "therapeutic window" is a measure of the drug's safety. It is the relationship between beneficial & adverse effects of a medication |
| Intolerance/side effect | adverse effect of a drug that limits its usefulness or acceptance in a patient |
| Drug Allergy | Immune system mediated response, non-dose related, unpredictable. i.e) rash, hives, itching |
| Name the variables that affect Absorption | -infant skins is much more absorbent -broken or rashy skin or hot/sweaty/moist skin is more absorbent -patients with bowel resections -Diarrhea or Constipation -(anything affecting GI motility) -stomach acidity -presence or absence of food |
| Name the variables that affect Vd & Distribution | -body comp. of infants has a larger %of water & lesser %of muscle mass - Obese patients may have a higher than expected vol. for drugs that are distributed into adipose tissue - Malnourished pt. -neonates & elderly have more permeable BBB |
| Name the variables that affect clearance (Metabolism/Excretion) | -Neonates have immature metabolic pathways &renal function -Infants & children have high liver metabolim and excretion rates -natural decline in liver enzyme & renal excretion activity w/age -hepattitis or alcohol abuse -interacting medications -gene |
| Name the Chemical factors that affect Absorption (bioavailability) | -lipid soluble (must be both lipid & water soluble for adequate GI absorption -liquid>chewable>tablet/capsule>enteric coated>sustained release -The larger the surface area the faster the absorption -Greater the blood flow the faster rate of absorption |
| Discuss the various routes of adminstrations and its effect on bioavailabity | -Normal dose differs IV vs. oral -Effectiveness differs IV vs. oral, rectal, topical, etc. -With food vs. empty stomach |
| List and explain the different areas of Drug Distribution | -BBB: only lipid soluble drugs can cross BBB & reach CNS -Placental barrier: lipid soluble drugs can cross & reach fetus -Breast milk: most drugs can enter a nursing mother's milk supply -fluid areas & lipid tissues |
| Because a infant has a larger % of water & lesser % of muscle mass than adults what change in dosage should occur? | Should give infants higher does of water soluble drugs |
| Because obese patients have a larger than expected Vd for durgs that are highly distributed into adipose tissue what change in dosage should occur? | Should give obese patients a higher dose of lipid soluble drugs |
| Since malnourished patients may have less serum proteins (albumin) available for drug binding what should be done in dosing for this patient? | Should give the malnourished patient a lower dose because if given the 'normal' amount it will have a higher affect |
| List the 4 mechanisms for drug interactions | 1. Direct chemical interaction 2. Pharmacokinetic interactions 3. Pharmacodynamic interactions 4. Combined toxicity |
| List strategies to Prevent DI's. | -Get a complete med. history -Be familiar w/ common drug interactions & adverse effects -avoid use of unnecessary drugs -select a non-interacting med -separate chelating or pH interacting drugs by at least 2 hours -monitor close when add or delete m |
| Define High Risk Drug and give examples | Those with a narrow therapeutic index, high incidence of adverse effects, or high incidence of allergic reactions i.e) penicilin, chemotherapy |
| Define High Risk Patients and give examples | Those that would be least likely to tolerate adverse effects or loss of efficacy. (individualize doses) i.e) pediatrics, elderly, frail, poor health |
| What is the object of Drug therapy? | Provide the maximum benefit with the minimum harm. |
| Name other considerations for drug therapy. | -Is drug therapy even necessary? -How effective is the drug? Risk/benefit -Can/will the patient be compliant? -Can the pt. afford it? Does the pt. understand? -When is the endpoint of drug therapy? |
Created by:
stullis
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