Term
| Components of physiologic disposition of drugs |
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Definition
- principle processes
- pharmacokinetics (describe time-dose relationship)
- clinical pharmacology
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Term
| What are the principle processes of physiologic disposition of drugs? |
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Definition
absorption
distribution
metabolism
excretion |
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Term
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Definition
| Process of getting the drug into the central compartment aka the blood |
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Term
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Definition
| getting from central compartment aka the blood to various tissues of body |
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Term
| Barriers to central compartment aka blood |
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Definition
- lipid membranes
- metabolic inactivation in some cases
- chemical interactions
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Term
| Main way drugs are absorbed |
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Definition
| diffusion (but there are many other ways as well) |
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Term
| What does diffusion depend on? |
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Definition
- area of membrane
- thickness of membrane
- concentration gradient
- lipid solubility
- partition coefficient
- measured by ability to distribute between organic and water particles
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Term
| Process of drug going through body |
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Definition
- drug undergoes dissolution
- drug is absorbed
- must cross other membranes to get to receptors
- two ways to eliminate
- metabolism in liver
- excretion (could be reabsorbed in kidneys)
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Term
| Relation between partition coefficient and absorption/diffusion rate |
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Definition
| the larger the partition coefficient, the more rapid the absorption |
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Term
| Relation between diffusion and ionization |
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Definition
- ionized molecules do not go across the membrane by simple diffusion
- only unionized form of molecule can diffuse across the membrane
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Term
| what is the final equilibrium concentration of a drug dependent on |
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Definition
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Term
| Describe the different types of ionization states of drugs |
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Definition
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neutral compounds
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weak acids
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weak bases
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Term
| What forms of the weak acids and bases tend to cross the membrane? |
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Definition
- HA (acid form with H)
- B (base without H)
aka, THEY ARE NOT CHARGED (they are unionized) |
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Term
| Aspirin is a weak acid. What kind of pH would it be in its active form in? |
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Definition
| a low pH (but not extreme) (increase H leads to increase in HA form due to LeChate's principle) |
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Term
| At what pH are weak bases most effective? |
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Definition
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Term
| When pH = pKa what can we say about the relative concentrations of ionized to unionized drug |
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Definition
| the concentrations of ionized to unionized drugs are equal |
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Term
| Effect of pH gradient (aka pH on each side of membrane) on drug concentration |
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Definition
-
if pH on either side of the membrane is the same, the total amounts of drug on each side of the membrane are the same
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if pH on either side of membrane different, there will be a difference in the amount of total drug across membrane (aka ion trapping/pH partitioning)
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Term
| Effect of placing base in lower pH |
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Definition
increase in the "BH" form (weak bases get trapped in acidic environments) |
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Term
| Effect of placing weak acid into a more basic pH |
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Definition
| increase in the A- form (trapping of A- form tends to happen at weak basic pH's) |
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Term
| Weak acids more likely to absorb at what kind of pH? weak bases |
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Definition
- weak acids need acidic pH's to absorb quicker
- weak bases need basic pH's to absorb quicker
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Term
| Role of molecular size of drug absorption |
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Definition
- larger molecules like protein use pinocytosis (which is very slow)
- very small molecules that are water soluble can use water channels or pores
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Term
| Effect of a drug being low protein binding in nature? high protein binding |
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Definition
- low protein binding drugs tend to be filtered and eliminated in the kidney
- high protein binding drugs (their weight is drug weight + albumin) are not filtered in the kidney, so it stays around longer
BUT ONLY THE FREE DRUG CAN CROSS THE MEMBRANE |
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