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38 Cards in this Set
- Front
- Back
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What does Agonist potency depend on?
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Affinity (tendency to bind to receptors)
Efficacy (ability, once bound, to initiate response) |
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What is the efficacy of an antagonist?
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zero (note: affinity can be greater than zero!)
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What is the difference between a full agonist and a partial agonist?
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Full agonist can produce maximal response. Partial agonist can only produce a partial response.
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What is the magnitude of a dose response dependent on?
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1. Amount of ligand
2. Number of receptors 3. Ligand Affinity 4. Affinity of Ligand-Receptor for Second messenger system 5. Amount of 2nd messenger |
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What is Competitive Antagonism?
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Both drugs bind to same receptor. Can be reversible or irreversible.
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What does Calvulanic Acid do?
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Irreversably inactivates Beta-lactamases (which themselves irreversably inactivate penicillins)
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What is the selectivity of a drug?
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specific action on one type of cell or tissue to produce only one type of effect
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What factors contribute to pharmacodynamic selectivity?
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1. Size and shape of drug.
2. Types of ionic change. 3. Ability to form Hydrogen bonds. 4. ability to attach at multiple points to receptor |
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What is the Therapeutic Index?
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Lethal Dose 50 / Effective Dose 50
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Why are toxic and therapeutic effects usually separable?
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1. Respective mechanisms of production
2. Dose-response relationship 3. Sites at which they are produced |
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What is Pharmacokinetics?
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What the Body does to the Drug.
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What is Pharmacodynamics?
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What the Drug does to the Body.
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What pharmacokinetic processes affect drug distribution?
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Absorption
Tissue Reservoirs Excretion Biotransformation Bound Drug |
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Does PK AUC for IV administration of a drug depend on absorption rate?
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No. IV administration bypasses routes of absorption
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What is Bioavailability of a drug?
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The extent to which a drug is absorbed and reaches systemic circulation.
F = AUC(oral) / AUC (iv) |
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What are some factors that reduce bioavailability after oral administration?
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1. Drug unstable in GI fluid (ie penicillin)
2. GI contents interfere with absorption 3. Drug is charged 4. First Pass Effect (biotransformation) |
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Which drug is more difficult to administer, one with a wide therapeutic range or one with a narrow therapeutic range?
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Narrow therapeutic range
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What is significant about Phenytoin (PTH)?
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narrow therapeutic range & nonlinear pharmacokinetics
ie. small change in bioavailability can lead to clinically significant change in PTH plasma levels |
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What does decreasing the rate of absorption do to the elimination rate?
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slows it down. elimination rate is directly proportional to absorption rate
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What is a zero order rate?
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ideal plasma concentration after administration of a drug. extended release has smaller Cmax and Cmin levels and therefore approaches this rate.
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What kinds of species can diffuse across lipid membranes of cells?
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nonionized
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What is the ionized form of Aspirin?
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Aspirin is a weak acid, so ionized form is negatively charged.
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What is the ionized form of Cocaine?
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Cocaine is a weak base, so ionized form is positively charged.
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Why are weak acids more easily absorbed in the stomach than weak bases?
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Weak acids are generally uncharged in the acidic stomach which allows them to pass through the membrane. The higher pH of the blood then ionizes them which makes it difficult for the drug to leave the blood -- stays there longer.
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What is pH partition?
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weak acids tend to accumulate in compartments of high pH while weak bases tend to accumulate in compartments of low pH.
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What is the main factor that determines rate of passive diffusion of a drug across a cell membrane?
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lipid solubility
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What happens if you increase pH of urine?
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weak acids will be trapped in the urine, however weak bases will be more readily reabsorbed.
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What plasma proteins bind to drugs?
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Albumin --> acids
Beta-globulin and acid glycoprotein --> bases |
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What does Phase I metabolic reactions do to drugs?
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Make a lipid soluble molecule MORE POLAR:
Add: -OH, -NH2, -SH Replace methyl with hydroxyl or amine |
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What does Phase II metabolic reactions do to drugs?
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MORE POLAR by adding:
Glucuronic acid Acetic acid Glutathione Glycine Sulfuric Acid Water |
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What are the consequences of a Phase II metabolic reaction?
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1. detox
2. increased renal elimination |
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How did P450 get its name?
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Carbon monoxide difference spectrum peak @ 450 nm
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What does CYP1A2 do?
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Detoxify toxic chemicals and carcinogens
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What does CYP2D6 do?
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Codeine to Morphine metabolism
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What does CYP2E1 do?
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Alcohol metabolism
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What does CYP3A4 do?
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Involved in the metabolism of many drugs
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What does it mean that CYP enzymes are selective but not specific?
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A single drug metabolism is performed mainly but not exclusively by one CYP enzyme.
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Which is more dangerous, CYP induction or CYP inhibition?
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CYP inhibition is more dangerous because it can cause drugs to remain in the system for longer than expected.
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