Pharmacokinetics
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| List the four pharmacokinetic processes | Absorption, distribution, metabolism, excretion
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| What factors affect drug absorption? | Rate of dissolution/absorption, surface area, blood flow, lipid solubility, pH partioning
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| What is the most common method drugs use to pass through membranes? | Direct penetration across membrane
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| True or false: to pass channels/pores, drug must go against a concentration gradient, using energy | FALSE. Drugs passed using transport system proteins. With channels, drugs go down a concentration gradient
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| Do charged/ionized molecules directly pass through membranes? | No, because they are hydrophilic
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| What type of drugs can cross membranes easily? | Lipid-soluble drugs
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| How does ionization of drugs help drugs pass between membranes? | By manipulating the pH gradient between two sides of a membrane
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| Acidic drugs will accumulate on ____ side | alkaline
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| Define ion trapping | Weak acid or base moves across membrane due to change in pH, becomes charged, then drug accumulates on one side due to change in charge
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| What does parenteral mean in a pharmacological context? | By injection
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| What are the principal parenteral routes? | Intravenous, subcutaneous, intramuscular
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| Which type of administration results in rapid or slow pattern of absorption? | Intramuscular, subcutaneous
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| What are the barriers for intravenous administration? | None
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| What are the advantages of IV administration? | Rapid onset, precise control over amount, suitability for use with large volumes of fluid and irritant drugs
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| What are the disadvantages of IV administration? | High cost, difficulty, inconvenience, danger because of irreversibility, and potential for fluid overload, infection, embolism
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| What are the advantages of IM/subQ administration? | Suitability for water-soluble drugs and suitability for depot preparations
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| What are the disadvantages of IM/subQ administration? | Inconvenience and potential for discomfort
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| What are the advantages of PO administration? | Ease, convenience, economy, safety
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| What are the disadvantages of PO administration? | High variability, possible inactivation by stomach acid, digestive enzymes, and liver enzymes.
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| True or false: preparations of a drug do not have the same bioavailability if they are absorbed at same rate and same extent | False
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| What are the factors affecting drug distribution? | Blood flow to tissue, capillary beds, blood-brain barrier (lipid-soluble), placental drug transfer, protein binding
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| Is binding to albumin reversible? | Yes
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| P450 proteins do what to drugs? | Metabolize by chemically modifiying. Can result in toxic metabolite buildup if there are toxic levels of drug.
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| Drug metabolism helps with accelerated drug (A), drug (B), increased (C), activation of (D), and (E) variations | (A) excretion, (B) inactivation, (C) therapeutic action, (D) prodrugs, (E) toxicity
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| At what age does the liver fully develop metabolizing capacity? | After 1 year
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| What is the first-pass effect? | Rapid hepatic inactivation of certain PO administered drugs. (Meaning drug never reaches site of action)
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| What are the three renal processes for drug excretion? | Glomerular filtration, passive tubular reabsorption, active tubular secretion
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| What are some examples of nonrenal drug excretion? | Bile, breast milk, lungs, sweat, saliva
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| Why monitor plasma levels to determine therapeutic range? | Plasma levels easiest to accurately measure
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| What is the difference between loading dose and maintenance dose? | Loading dose is a large initial dose of drug used to achieve plateau more quickly. Maintenance dose keeps drug levels at plateau.
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| Define drug half-life | The time for amount of drug in body to decrease by 50%
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| Explain why drug-metabolizing enzymes have therapeutic consequences | A drug can increase rate of its own metabolism, necessitating increase in dosage to maintain therapeutic effects. Drug-metabolizing enzymes can accelerate metabolism of other drugs, which necessitates increase in their dosages too.
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| True or false: enteric-coated oral formulations are designed to release their contents in stomach | False. Designed to release in small intestine
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| True or false: membranes of placenta constitute an absolute barrier to passage of drugs | False. Same factors determine drug movements across all other membranes apply
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| What is the blood-brain barrier describing? | Tight junctions between cells that compose capillary walls of CNS. Drugs must pass through cells of capillary wall to reach CNS instead inbetween.
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| What is enterohepatic recirculation? | Drugs entering intestine in bile can be reabsorbed back into portal blood
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| How many half-lives does it take for a drug to be cleared or reach a plateau? | 4
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| If plasma drug levels fluctate too much, what three interventions can be used? | 1) give smaller doses at shorter intervals with same total daily dose; 2) use continuous infusion, 3) use a depot preparation
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| True or false: drug A is given at 100x the dose of drug B. Drug A will take more time to reach plateau | False. Time to reach plateau is independent of dosage size
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