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Pharmacology Test 1
Don's Pharm Lectures
| Question | Answer |
|---|---|
| Pharmacology | The study of substances that interact with living systems through chemical processes (pharmacokenetics and pharmacodynamics |
| Pharmacodynamics | Describes what the drug does to the body |
| Pharmacokinetics | Describes what the body does to the drug |
| Absorption | Amount of drug that gets into the blood stream following administration |
| Disposition | Distribution, metabolism, and elimination |
| Describe the nature of drugs | A substance that causes a change in biological function through chemical reactions; usually deals with specific chemicals interacting with specific molecules; may also deal with drug-drug and drug-water reactions |
| What affects a drugs ability to reach its site of action? | Solubility |
| What is the average size of most drugs? | 100-1000 |
| What size of drugs are the most selective? | Large molecular weight |
| What is an advantage of large molecular weight drugs? | More selective and less side effects |
| What siz of drug is the least selective? | Small Molecular weight |
| What is the first step in pharmacokenetics? | The drug must reach the target tissue |
| What ae the step in pharmacokenetics? | Drug reaches target tissue, absorption of the drug, disposition (distribution, metabolism, elimination) |
| What is required in order for a drug to work, unless it is administered directly to the target tissue? | Permeation |
| What are the 4 primary mechanisms of permeation? | Aqueous diffusion, lipid diffusion, special carriers, endocytosis/exocytosis |
| What law describes a main part of aqueaous diffusion? | Ficks Law |
| Which form of a drug is water soluble? | Ionized |
| Which form of a drug is lipid soluble? | Unionized |
| What is the most important limiting factor for diffusion speed and why? | Lipid solubility because there are a large number of lipid barriers in the body |
| True or False: Most drugs exist in both ionized and unionized forms | TRUE |
| What characteristic of a medium can affect the absorption of a drug? | pH |
| In a closed system what is the ratio of ionized to unionized particles? | 1:5 |
| Describe the reaction of an ionized particle in water | The charged particle attracts the dipoles of the water and becomes a polar water soluble complex (lipid insoluble) |
| Describe Ion Trapping | |
| Describe a weak acid's solubility properties | When protonated (DrugH) it is unionized and lipid soluble; when unprotonated (Drug- H+) it is ionized and water soluble |
| What pH of a solution will allow for a weak acid drug to be more soluble and why? | Acidic pH because the drug is less likely to dissociate and become ionized, so it will remain lipid soluble |
| What is the neutral (unionized) form of a weak acid? | Protonated (DrugH) |
| Describe a weak base's solubility | when protonated (DrugH+) it is charged and water soluble; when unprotonated (Drug H+) it is uncharged and lipid soluble |
| What pH of a solution will allow a weak base drug to be more soluble and why? | Basic pH; In base pH there are less H+ ions to take on and therefore the drug will stay unionized and more lipid soluble |
| What is the neutral (unionized) form of a weak base? | Unprotonated (Drug H+) |
| What are the genera characteristics of a weak base (functional groups, charge of particles) | Nitrogen with 3 groups (NH3); OH-, negative ions (except Cl-, Br-, H2SO4-, H2PO4-) |
| What are the genera characteristics of a weak acid (functional groups, charge of particles) | Begin with H, Mostly Cations, COOH at end, NH4 |
| When describing movement to the left, what type of drug will you see? | Protonated |
| When describing movement to the right, what type of drug will you see? | Unprotonated |
| What reaction tends to occur in an acid environment? | Shift to the Left (Protonation) |
| What reaction tends to occur in a base environment? | Shift to the Right (Unprotonation) |
| How does alkylizing urine increase excretion of a weak acid drug? | When a weak acid drug crosses into the alkylotic urine it becomes unprotonated and charged and cannot be reabsorbed |
| Describe primary, secondary and tertiary amines | They have 1,2,&3 carbons, respectively. They have unshared pairs of electrons. They may be protonated or unprotonated depending on the pH of the medium |
| Describe a Quateranary Amine | It is always charged and water soluble. It does not cross lipid membranes |
| Ho do large or lipid insoluble molecules cross barriers? | Special carriers |
| What type of molecules act as special carriers? | Peptides, Amino Acids, Glucose |
| What are the limiting factors of special carriers? | They are saturable and they can be inhibited |
| True or False: Increasing the dose of a medication in a person who has saturated carriers will increased the therapeutic action. | FALSE |
| Describe endocytosis and give examples | Molecule is engulfed by a cell; Iron and Vitamin B |
| What is exocytosis and give an example | Releasing of a molecule by a cell; ACh |
| What are the 3 major types of bonds found in drugs? | Covalent, Electrostatic, Hydrophobic |
| What are the strongest type of bonds found in drugs? | Covalent |
| How long do covalent vonded drugs last in the body? | They stay in the body until the cell dies. |
| Give an example of a covalently bonded drug | Chemo |
| Describe Electrostatic bonds | More common than covalent; Ionic molecules with H bonds; Weak dipole interaction |
| What are the forces called that keep electrostatic bonds together | Van der Waal forces |
| Describe Van der Waal forces | Intermolecuular forces related to polarization of molecules into dipoles; non-uniform distributions of positive and negative charges on various atoms |
| Where do hydrophobic bonds occur? | Between lipid soluble drugs and lipids of cell membranes |
| Describe the characteristics of a hydrophobic bond | Weak; generally more selective; short acting |
| Describe how drug shape affects the effectiveness of a medication | Permits a drug to bind to a specific site; Isomers differ in their potency |
| Describe the effect that drug shape has on enzymatic breakdown of a particular drug | Enzymes are stereoselective and may only breakdown one form of the drug |
| What is an agonist? | A molecule that mimics the action of another drug |
| How does an agonist work? | It binds to a drug receptor and activates the receptor |
| Describe a direct agonist | Medication binds directly to the receptor site and causes an action |
| Describe an indirect agonist | Medication that increases the amount of endogenous molecules, so there are more available to bind with receptors to cause an action |
| Describe how an inhibiting agonist works | It blocks the actions of molecules responsible for stopping the action of an endogenous agent |
| Describe a partial agonist | A molecule that evokes a lesser response than endogenous molecules at receptor sites |
| Describe Affinity | The ability to bind to a receptor |
| Describe the affinity constant | It is the drug receptor concentration that produces 50% occupancy of the receptors |
| The higher the affinity constant the __________ the drug concentration neede to produce a desired effect | Lower |
| Describe Efficacy | The amount of drug required to cause a therapeutic response (potentcy) |
| True or False: There is a direct relationship between affinity and efficacy | FALSE |
| How do antagonists work? | They bind to a recepor preventing the binding of other molecules; they reduce the effects of other molecules in the body |
| Antagonists have _____________, but no___________ | affinity; Efficacy |
| Wht are the 2 types of antagonists | Competitive and Noncompetitive |
| Describe the properties of a competitive antagonist | It competes for receptors with an agonist to fill the receptor and cause no action |
| How do you increase antagonism with a competitive antagonist | Increase the concentration of the antagonist |
| Is it possible o reach the desired effects by increasing the concentration of either agonist or competitive antagonist? | YES |
| Describe the properties of a non-competitive antagonist | 2 totally different molecules bind to different receptor sites on the same molecules; One site activate the other inhibits |
| What is one distinguishing factor of non-competitive antagonists? | Increasing the concentration does NOT change the action of inhibition. (It is determined by efficacy only) |
| Describe drug antagonism | One drug binds to another drug rendering them both unavailable for other reactions |
| Describe the factors that effect the duration of a drug | Effect ends when drug leaves receptor; activation of receptor may persist if coupling molecule i present; covalent bonds last until drug-receptor complex is destroyed |
| Why is the desensitization mechanism important? | It prevents excessive activation of receptors. (this is why people develop drug tolerances) |
| What factors determine therapeuticity and toxicity? | Dose, Clearance pH, Binding to receptors, expected action |
| Describe the 1 compartment model for volume of distribution | ↑ Lipid solubility = ↑ Volume of Distribution; ↓ Lipid solubility = ↓ Volume of Distribution; ↑ Size of molecule = ↓ Volume of distribution |
| What is Volume of Distribution? | The extent of the drug's extravascular distribution at equilibrium |
| What can cause a low Volume of distribution | ↓ lipid solubility, excessive protein binding |
| What can cause a high Vd? | ↑ Lipid solubility; ↓ Intravascular protein binding |
| What is clearance? | The measure of the ability of the body to eliminate a drug |
| Describe Half-Life | The time required to decrease the amount of drug in the BODY by 50% during elimination |
| The slower the clearance, the ____________ the 1/2 time | Longer |
| The more Vd the ___________ the 1/2 time | Longer |
| When would 1/2 life and 1/2 time not parallel each other? | When Vd is ↑ because the drug has to enter back into plasma to be cleared, and if it is widely distributed that will take longer. |
| How many 1/2 times equal 96% elimination? | 5 |
| Describe 1st order Kenetics | The amount that is cleared is proportional to the amount of drug given |
| Describe Zero order kenetics | Total amount of drug elimination is not proportional to the amount of drug in the body because there is a set clearance rate. |
| When can 1st order kinetics convert to zero order? | Once the maximum excretion rate is reached, 1st order switches to zero order. |
| Describe a context sensitive 1/2 time | Length of time for plasma concentrations of a drug to fall to 50% following a drip |
| What organs are involved in elimination? | Kidneys, Liver, Lungs, Blood, Muscle |
| Describe first pass metabolism | PO meds are absorbed from small intestine and enter portal circulation where they reach the liver and are metabolized weakening them for use in the body |
| Describe capacity dependent elimination | It has a low hepatic extraction ration (<0.3); It relies on enzymes excreted by the liver for breakdown of the drug. |
| Describe perfusion-dependent elimination | It has a high hepatic extraction ratio (>0.7); It is dependent on hepatic blood flow (cardiac output); It is broken down by LIVER |
| Describe billiary excretion process | It is usually perfusion dependent; The live breaks down drug and metabolites and excretes them in bile into the GI tract; Then metabolites are reabsorbed and eliminated in the urine. |
| What consideration should be made in respect to metabolites | Are they active or inactive |
| What type of drugs are most easily excreted by the kidneys? | Ionized because they are water soluble. |
| How can you increase the renal excretion of a drug? | Change the pH of the urine |
| What are the 3 major processes in renal elimination? | Glomerular Filtration, Active Tubular Secretion, Passive Tubular Reabsorption |
| What factors effect renal clearance of a drug? | GFR, Protein binding,Ionized metabolite, urine pH |
| What must occur to lipophillic drug in order for it to be eliminated? | It must be metabolized into a hydrophillic molecule |
| What are the 4 basic pathways of metabolism? | Oxidation, reduction, hydrolysis, conjugation |
| What are the Phase I reactions? | Oxidation, Reduction, Hydrolysis |
| What is the phase II reaction? | Conjugation |
| What are the possible outcomes of a phase I reaction? | Drugs become inactive; Prodrugs are converted to active metabolites; Functional group attachment makes drug more water soluble |
| What enzymes are involved in Phase I reactions? | Cytochrome P450, NonCytochrome P450, Flavin-containing monooxygenase enzymes. |
| Phase I reaction products may be ___________ (there are 2 routes) | Excreted in urine or react with endogenous compounds to form water soluble conjugates |
| What happens in a phase II reaction? | Parent drug forms a covalent bond wih another function group that is polar and water solubale, generally inactive and rapidly excreted in the urine |
| What functional groups participate in phase II reaction? | Glucuronic Acid, Sulfate, glutatione, amino acids, acetate |
| What is the principle organ for durg metabolism? | Liver |
| What are the non-principle organs for drug metabolism? | Kidneys, Lungs, GI Tract, Skin |
| Describe Biotransformation Sequence I | PO administration absorbed by small intestine and enters portal circulation where it goes to the liver and undergoes extensive metabolism (First Pass Effect)PO administration |
| Dscribe Biotransformation Sequence II | PO administration and absorbed by small intestine and metabolized by small intestine (contributes to first pass effect) |
| What is the other name for CP450? | Mixed function oxydase system |
| Where are CP450 Enzymes Found? | Lipophillic HEPATIC smooth ER; also found in other membranes |
| What type and phase of reaction occurs with CP450 | Phase I, Redox |
| Describe a Redox Reaction | Chemical Proces in which atoms have their oxidation number changed |
| Oxidation Number | The charge of an element if all of the electron pairs that were shared with a central atom were removed. |
| Oxidation | Loss of an electron |
| Reduction | Gain of an electron |
| Describe the 1st stage in CP450 oxidase | Substrate (drug) binds to CP450 and lowers the redox potential (goes to redox state more easily) which allos for tranfer of an electron from its partner (NADH or NADPH) to the substrate (drug) |
| Tie Stage I CP450 to phase I reaction | Functional groups (OH-, NH2-, SH-) react with drug to be excreted in urine or confugated (phase II) |
| What causes CP450 induction | Repeated exposure to certain drugs |
| What 2 proceses cause CP450 Induction | ↑ CP450 synthesis rate or ↓ break down of CP450 |
| How can CP450 be inhibited? | Some drugs competitively inhibit binding sites; some drugs' metabolites inactivate CP450 |
| here do phase II reaction occur? | non-microsomal enzymes foundprimarily in the liver with some in the plasma and gut |
| What is the advantage of plasmaesterase metabolism? | It is not dependent on liver function or BP |
| What are the characteristics of a conjuation reation? | Usually detoxification reaction, usually mor polar, easily excreted, typically inactive |
| What are the 5 types of conjations | glucuronidation, acetylation, glutathione conjugation, sulfate conjuation, methylation |
| Describe how glucurondiation works | glucuronic acid with help from CP450 cojugates to lipid soluble drug and results in lipophilic glucuronic acid derivative that is MORE water soluble |
| Describe how APAP Toxicity occurs | Once Glucuronidation + sulfation pathway is saturated, the CP450 metabolizes the APAP and produces toxic metabolites. There is no saturation level for CP450 metabolism. |
| What is an inert Receptor? | Receptor in the body that binds to drugs, but the drug does not elicit its effect |
| What is the most abundant inert receptor in the body? | Plasma Albumin |
| What are the 1 major changes that occur in receptors? | Down regulation and internalization |
| Describe how receptor phosphorylation works | G-protein coupled receptor kinases increase the receptors affinity for arrestin which prevents further signal transduction |
| What is the result of receptor phosphorylation? | Decreased affinity of receptors and weakened receptor function so there is less of a response elicited |
| Describe internal sequesteration of receptors | Receptors are taken into cell, some are degraged by lysosomes and others are recycled back to surface of plasma membrane unchanged |
| Describe receptor down regulation | Decrease in the number of receptors available |
| Describe 1/2 Time | Time necessary for the PLASMA concentration of a drug to decrease by 1/2 during elimination |
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