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25 Cards in this Set
- Front
- Back
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Most drugs in solution are either _____ or ________, or ________ or _________
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weak acids or weak bases,
nonionized, ionized |
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the ___form of drug is more lipid soluble
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nonionized
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The ______ at a site determines the degree of ionization
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pH
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HH Equation for an acid:
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pKa=pH + log [HA]/[A-]
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HH Equation for a base:
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pKa=pH + log i/n
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The degree of ionization is important where great changes in pH such as:
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stomach, and in urine
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What is ion-trapping?
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at equilibrium, the total drug (n+i) is greater where conditions favor ionization (weak acids)
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What are some well perfused organs?
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Brain, lungs, liver
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What are some poorly perfused organs?
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bone and adipose tissue
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What is the effect on glomerular filtration of protein binding?
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Less filtered-only free drug is filtered (not important if in kidney/liver)
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_____binds acidic drugs such as acetylcholine, barbiturates, penicillin, salicylates, sulfonamides, streptomycin, tetracyclines, warfarin
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Albumin
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_____ binds basic drugs such as Vit. B12, thyroxine, glucocorticoids
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a1-acid glycoprotein
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____ fluctuates rapidly and varies among patients with age, stress, inflammation
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a1-acid glycoprotein
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Name three drugs that bind to the a1-acid glycoproteins:
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Vit B12, thyroxine, glucocorticoids
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2 other glycoproteins:
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CBG, TBG coticosteroid and thyroxine binding globulin
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2 major factors inhibit CNS drug distribution:
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BBB, CSF production carries it right out of cells
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Transplacental distribution affected by:
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lipid solubility, simple diffusion
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3 other drug distribution barriers:
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prostate, testicles, eye globe
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Area of trapezoid:
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time*(h1+h2)/2
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What is bioavailability?
F |
fraction of drug that enters systemic circulation
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Formula for Amount of drug reaching systemic circulation:
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A= F*S*Dose
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Equation for equivalent dose:
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Dose of new=Amount absorbed old/S*F of new form
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Volume of distribution formula:
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Vd=(dose*F*S)/drug concentration initially achieved
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Loading dose equation:
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Loading Dose= [Vd*patients weight in kg*Cpdesired]/S*F
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Loading dose if want to ramp up loading dose:
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Ld=[Vd*pts weight kg*(Cpdesired-Cpinitial)]/S*F*
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