Biopharmceutics Pharmokinetics

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Biopharmceutics Pharmokinetics
2012-02-02 00:01:40
Lecture III

Lecture III
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  1. For first order kinetics what is the elimnation rate equal to?
    rate= v= [Drug plasma] * k

    k= is the elimnation rate constant
  2. 1st order kinetics what is drug elimnation equal to?
    [drug plasma] * drug clearance
  3. What happens to the elimnation rate with a decrease in [drug] with 1st order kinetics?
    the elimnation rate decreases with a decrease in [drug]
  4. What happens to t1/2 and cl with a decrease in [drug] 1st order kinetics?
    half life and clearance remain the same if hepatic and renal function do not change
  5. What is t1/2?
    the time it takes to decrease the plasma concentration by 50%
  6. t1/2= (equation we need to know)
    t1/2= 0.693/k
  7. What are the factors that affect t1/2 ?
    Drug clearance rate

    Volume of distribution

    Disease or age
  8. Cl = (equation we need to know)
    Cl = Vd * K
  9. What is the rate emlination during zero order kinetics?
    It is constant
  10. Are zero order reactions dependent on concentration?
    INdependent of concentration of drug in plasma
  11. What are the things posted on Baskis slide about metabolism?
    Drug molecules are metabolized by enzymes

    Drug action may increase/decrease after metabolism

    Genetic variations determine the fate of the drug

    Several routes of metabolism for drugs

    May or may not terminate the action of the drug

    May take place anywhere but the liver is the prime site

    Not contant, can be changed by other drugs basic of drug
  12. Where are the sites of biotranformation?
    Where ever the appropiate enzymes occur, plasm, kidney,gut wall and the liver is the ideal place to metabolize drugs and has a major role in biotransformation
  13. What is the main enzyme for metabolism?
    Cytohrome P450, had mix function of oxidases, there are 4 fmailies, six sub families, and 20 isoenzymes
  14. What is the order of phase 1 reactions?


    • N-de-alkylation
    • Oxidative deamination
  15. What does an oxidation reaction do?
    increase in the proportion of oxygen
  16. What does a reduction reaction do?
    decrease in the proportion of oxygen
  17. What does a hydrolysis reaction do?
    Cleavage by the addition of water
  18. What is the phase 2 reactions?
    Conjugations with glucuronide, sulphate
  19. What does conjugation of glucuronide, sulphate do?
    Alters activity, made less lipid soluble so excreted
  20. What are the factors that effect biotransformation?




    • Clinical or physiological condition
    • Other drugs administerd


    First pass metabolism
  21. What are high risk patients for drug interaction?

    • Young
    • Very Sick

    Multiple Disease

    Multiple drug therapy

    Renal, liver impairment
  22. What are high risk drugs for drug interaction?
    Narrow therapeutic index

    Enzyme inhibitor or inducer
  23. What are some drugs with low therapeutics index?







  24. What is the definition of drug interaction?
    ONe drug may alter the extent of absorption, distribution, metabolism, or excretion of another drug

    A change in blood concentration of one drug may cause a change in the drugs effect
  25. What is enzyme induction?
    LEads to the production of more enzymes usually 3 to 4 days of exposure to an inducer
  26. What does the time course of an inducer depend on?
    the half life of the inducer
  27. What are some drug interactions with excretion?
    • Drug A can increase or decrease the excretion of drug B
    • Which causes drug B fall below or rise above normal therapeutic range

    Can lead the drug to be either toxic or ineffective
  28. What is drug displacement?
    Drug binding to plasma protein and not allowing to drug to get to tissue

    Only free drug can get to the target tissue

    Another drug can bind to the plasma protein displacing the first drug from the plasma protein allowing more free drug available to bind to tissue
  29. Define bioavailability
    the true rate and extent at which the therapeutically ative drug reaches the systemic circulation and is available at the site of action from an administered dosage form

    The proportion of drug in a dosage form available to the body
  30. How much drug is bioavailable for an IV injection?
    IV are 100 percent bioavailable
  31. What is the absolute bioavailability equal to?
    [AUC]po * does IV divided by [AUC]IV * dose po
  32. What is the relative bioavailability?
    [AUC]a *dose b divided by [AUV]b * dose a
  33. What is the pharmokinetic method of assessing bioavailability?
    It is based on the plasma concentration of the drug and the assumption that the pharmokinetic profile reflects the therapeutic effectiveness of a drug
  34. What is the pharmodynamic method of assessing bioavailability?
    Based on direct measurement of drug effect on a pathophysiologic process as a function of time
  35. What are some reasons for poor bioavailability?
    Poor aqueous solubility

    • Poor stability of the dissolved drug at physiological pH
    • Poor permeation through the biomembranes

    Extensive presystemic metabolism
  36. What are the methods of enhancing bioavailability?
    Lipids based formulation

    Size reduction, mirconization

    Functional polymer technology

    Porous microparticle technology

    The hydrophilic solubilization technology

    Controlled precipitation technology

    Inclusion complexes

    Solid Dispersions
  37. What is the lipid based formulation way to enhance absorption?
    Lipid solution

    high lipophilicity facilitates drug absorption

    The presence of surfactant in such formulations enhances absorption due to increase permeability
  38. What is the size reduction micronization way to enhance absorption?
    Increasing the surface area by decreasing the particle size gives a higher rate of dissolution
  39. What is the functional polymer technology way to enhance absorption?
    Ion exchange resins interact and exchange ions with ionizable molecules of the surrounding medium reversibily
  40. What is the porous microparticle technology way to enhance absorption?
    The hydrophobic drug delivery system

    The poorly water soluble drug is embedded into a porous water soluble mircoparticle.

    When in contact with water the matrix dissolves leaving a suspension of rapidly dissolving particles

    The particle have a large surface area
  41. What is the hydrophilic solubilization technology way to enhance absorption?
    THey are coated with lecithin-gelatin which form micelles to enhance dissolution
  42. What is the controlled precipitation technology way to enhance absorption?