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Principles of Pharm

Principles of Pharmacokinetics & Pharmacodynamic

QuestionAnswer
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