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13 Cards in this Set
- Front
- Back
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Ficks Law of Diffusion
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(area*permeability coefficient* diff in concentration) / thickness
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Hendersson-Haselbach equation
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Log ( protinated/ unprotinated)=pKa-pH
When pH is low for acidic drug more protinated lipid soluble form |
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Base can accept what?
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Protons
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Weak base
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A neutral molecule that can combine with proton to form a cation ie amomnium = ammonia + H^+
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k
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equilibrium constant. Large means favors products. small favors reactants ie ka = 9.6 therefore highly acidic it would take a pH of 9.6 to neutralize
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acid
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neutral molecule dissociates into negatively charged molecule and and proton. Neutral in protinated from bases are neutral in the protinated from
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completely unprotonated
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lack protons; ph greater than pka; HH is negative; pka= pH HH = 0
+protonated (acid lipo); - unprotonated (base lipo) |
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How do receptors determine quantitative relations?
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dictate drug affinity and concnetration large number of drug receptor complexes are formed and determine drug maximal effect
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Logarithmic graph of effect vs dose
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Dose-response data are often presented as a plot of the drug effect (ordinate) against the logarithm of the dose or concentration (abscissa). This mathematical maneuver transforms the hyperbolic curve of Figure 2–1 into a sigmoid curve with a linear midportion (eg, Figure 2–2). This expands the scale of the concentration axis at low concentrations (where the effect is changing rapidly) and compresses it at high concentrations (where the effect is changing slowly), but has no special biologic or pharmacologic significance.
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spare
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"spare" for a given pharmacologic response if it is possible to elicit a maximal biologic response at a concentration of agonist that does not result in occupancy of the full complement of available receptors
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degree of spareness
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the total number of receptors present compared with the number actually needed to elicit a maximal biologic response.
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ki
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antagonist concentration at which
agonist concentration in the presence of antagonist is twice that of without. |
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The degree of inhibition produced by a competitive antagonist depends on the concentration of antagonist. The competitive -adrenoceptor antagonist propranolol provides a useful example. Patients receiving a fixed dose of this drug exhibit a wide range of plasma concentrations, owing to differences among individuals in clearance of propranolol. As a result, inhibitory effects on physiologic responses to norepinephrine and epinephrine (endogenous adrenergic receptor agonists) may vary widely, and the dose of propranolol must be adjusted accordingly.
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Clinical response to a competitive antagonist depends on the concentration of agonist that is competing for binding to receptors. Here also propranolol provides a useful example: When this drug is administered at moderate doses sufficient to block the effect of basal levels of the neurotransmitter norepinephrine, resting heart rate is decreased. However, increase in the release of norepinephrine and epinephrine that occurs with exercise, postural changes, or emotional stress may suffice to overcome this competitive antagonism. Accordingly, the same dose of propranolol may have little effect under these conditions, thereby altering therapeutic response
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