University:
Michigan State University
Course:
PHM 802 | Cellular, Molecular and Integrated Systems Pharmacology
Academic year:

2019
Views:

443

Pages:

48
Author:

ViatDithDuada3f3

Pharmacologic Principles Definitions Drug: It is any chemical that affect living processes. It modifies an already existing function, and does not create a new function. 2 What is Pharmacology? Pharmacology is the study of drugs It involves examining the interactions of chemical substances with living systems, with a view to understanding the properties of drugs and their actions, including the interactions between drug molecules and drug receptors and how these interactions elicit an effect. Pharmacology   The study or science of drugs Knowledge of pharmacology allows us to understand how drugs affects humans. Naming the drugs  Chemical name: atomic/molecular structure  Generic   derived from chemical name listed in US Pharmacopedia & Formulary  Trade   name name selected by Manufacturer copyrighted Drug Names Chemical Generic Name Trade Name Name 7-chloro-1,3-dihydro-1methyl-5 phenyl 2H-1, 4-benzodiazepin 2-one diazepam Valium Ethyl 1-methyl 4-pheylisonipecotate hydrochloride meperidine Demerol acetylsalicyclic aspirin Ecotrin Dosage Forms        Tablets Capsules Sustained release tablet Injection – “shot” Sublingual – under the tongue Intravenous - IV or directly into the vein Topical Drugs have been discovered by two approaches Drug discovery phase:  Serendipity    Screening    Penicillin Sildenafil aspirin Statins/HMG CoA reductase inhibitors Design   HIV protease inhibitors COX2 specific inhibitors Phases of Clinical Investigation Phase I • • When a drug is administered to humans for the first time. Healthy men between 18 and 45 years of age • Can this be applied to all drugs?!!!! • The purpose of phase I studies is to establish the dose level at which signs of toxicity first appear. Phase II • Phase II: Drugs are given to larger group [100-300] to confirm effectiveness, monitor SE, & further evaluate safety Phases of Clinical Trials (cont.)   Phase III: New drug given to even larger group [1,000-3,000] to fulfill all of Phase II objectives & compare it to other commonly used txs & collect data that will allow it to be used safely Phase IV: Done after new drug has been marketed - studies continue to test and to collect data about effects in various populations & SE from long term use. Summary of Phases I-III Phase I # Subs. Length Purpose % Drugs Successfully Tested 20 – 100 Several months Several months- 2 yrs. Mainly Safety 70% Short term safety; mainly effectiveness 33% 1-4 yrs. Safety, dosage & 25-30% effectiveness Phase II Up to several 100 Phase III 100s – several 1000 Dr. Shatanawi 2017 Areas of Pharmacology • The main areas of pharmacology are: A. Pharmacodynamics: the study of the biochemical and physiological effect of the drugs and their mechanism of action. B. Pharmacokinetics: the way the body handle drug absorption, distribution, biotransformation, and excretion. Pharmacodynamics  Drug targets are usually receptors or enzymes. The drug needs to bind a sufficient number of target protein at a reasonable dose, so the drug should be potent.  The study of the biochemical and physiological effect of the drugs and their mechanism of action.  The study of the relationship of drug concentration to drug effects. Mechanism of drug action  Most drugs exert their effect by interacting with a specialized target macromolecules, called receptors, present on the cell surface or intracellularly.   The receptors will transduce the binding into a response by causing a conformational changes or biochemical effect. Mechanism of drug action  Receptors are large macromolecules with a welldefined 3D shape.  The two fundamental properties underlying specificity in drug-receptor interactions are complementarity of shape between drug and receptor, and complementarity between the electrostatic, hydrophobic, and hydrogen bonding surfaces of each component. Most receptors are proteins that have undergone various post-translational modifications such as covalent attachments of carbohydrate, lipid and phosphate. Definition of CELL SURFACE RECEPTOR: A receptor that is embedded in the cell membrane and functions to receive chemical information from the extracellular compartment and to transmit that information to the intracellular compartment. Major receptor families • Ligand-gated ion channels • G protein-coupled receptors • Enzyme-linked receptors • Intercellular receptors Ligand-gated ion channels • Responsible for regulation of the flow of ions channels across cell membranes. • Regulated by binding of a ligand to the channels. • The best example being the nicotinic receptor, in which the binding of the acetylcholine results in sodium influx and the activation of contraction in skeletal muscle G protein-coupled receptors • Receptors on the inner face of the plasma membrane regulate or facilitate effector proteins through a group of guanosine triphosphate (GTP) proteins known as G proteins. • Some hormones peptide receptors and neurotransmitter receptors (e.g., adrenergic and moscarinic receptors depend n the G proteins) mediate their action on cells. Enzyme-linked receptors • Binding of the ligand to the extra cellular domain activates or inhibits the related cytosolic enzyme. • The most common are the receptors that have a tyrosine kinase activity as part of their structure, in which the binding results in the phosphorylation of tyrosine residues of specific protein. • The addition of phosphate group can modify the threedimensional structure of the target protein, and so resulting in molecular switch. Intercellular receptors • In this family the ligand must diffuse into the cell to interact with the receptors. • Therefore the ligand must have sufficient lipid solubilities to be able to move across the target cell membranes. • The best example being the steroids hormones. In which the activated ligand-receptor complex migrate to the nucleus, where it bind to a specific DNA sequences, resulting in regulation of the gene expression. Receptors     determine specificity of drug action most are proteins Most drugs bind reversibly (noncovalent) not all “drugs” use receptors Characteristics of Drug-Receptor Interactions • • • • • • Chemical Bond: ionic, hydrogen, hydrophobic, Van der Waals, and covalent. Saturable Competitive Specific and Selective Structure-activity relationships Transduction mechanisms Lock and key HOW DO DRUGS WORK on RECE • Some antagonize receptors • Some activate receptors (Agonists) HOW DO DRUGS WORK BY ANTAGONIZING CELL SURFACE RECEPTORS? KEY CONCEPTS: • Cell surface receptors exist to transmit chemical signals from the outside to the inside of the cell. • Some compounds bind to cell surface receptors, yet do not activate the receptors to trigger a response. • When cell surface receptors bind the molecule, the endogenous chemical cannot bind to the receptor and cannot trigger a response. • The compound is said to “antagonize” or “block” the receptor and is referred to as a receptor antagonist. 36 HOW DO DRUGS WORK BY ANTAGONIZING CELL SURFACE RECEPTORS? Extracellular Compartment Unbound Endogenous Activator (Agonist) of Receptor Cell Membrane Inactive Cell Surface Receptor Intracellular Compartment HOW DO DRUGS WORK BY ANTAGONIZING CELL SURFACE RECEPTORS? Extracellular Compartment Bound Endogenous Activator (Agonist) of Receptor Cell Membrane Active Cell Surface Receptor Intracellular Compartment Cellular Response HOW DO DRUGS WORK BY ANTAGONIZING CELL SURFACE RECEPTORS? Displaced Endogenous Activator (Agonist) of Receptor Extracellular Compartment Bound Antagonist of Receptor (Drug) Cell Membrane Intracellular Compartment Inactive Cell Surface Receptor Upon being Bound HOW DO DRUGS WORK BY ANTAGONIZING CELL SURFACE RECEPTORS? Footnote: Most antagonists attach to binding site on receptor for endogenous agonist and sterically prevent endogenous agonist from binding. If binding is reversible - Competitive antagonists If binding is irreversible - Noncompetitive antagonists However, antagonists may bind to remote site on receptor and cause allosteric effects that displace endogenous agonist or prevent endogenous agonist from activating receptor. (Noncompetitive antagonists) HOW DO DRUGS WORK BY ANTAGONIZING CELL SURFACE RECEPTORS? Displaced Endogenous Activator (Agonist) of Receptor Extracellular Compartment Bound Antagonist of Receptor Cell Membrane Intracellular Compartment Active Receptor Inactive Receptor Allosteric Inhibitor Drug Receptor Interactions 42 Sep-17 Other Drug Targets • Antagonists of Cell Surface Receptors • Antagonists of Nuclear Receptors • Enzyme Inhibitors • Ion Channel Blockers • Transport Inhibitors •Inhibitors of Signal Transduction Proteins HOW DO DRUGS WORK BY ACTIVATING ENDOGENOUS PROTEINS? • Agonists of Cell Surface Receptors (e.g. alpha-agonists, morphine agonists) • Agonists of Nuclear Receptors (e.g. HRT for menopause, steroids for inflammation) • Enzyme Activators (e.g. nitroglycerine (guanylyl cyclase), pralidoxime) • Ion Channel Openers (e.g. minoxidil (K) and alprazolam (Cl)) HOW DO CHEMICALS WORK BY ACTIVATING CELL SURFACE RECEPTORS? KEY CONCEPTS: •Cell surface receptors exist to transmit chemical signals from the outside to the inside of the cell. • Some chemicals bind to cell surface receptors and trigger a response. • Chemicals in this group are called receptor agonists. • Some agonists are actually the endogenous chemical signal, whereas other agonists mimic endogenous chemical signals. HOW DO CHEMICALS WORK BY UNCONVENTIONAL MECHANISMS OF ACTION? •Disrupting of Structural Proteins e.g. vinca alkaloids for cancer, colchicine for gout • Being Enzymes e.g. streptokinase for thrombolysis • Covalently Linking to Macromolecules e.g. cyclophosphamide for cancer • Reacting Chemically with Small Molecules e.g. antacids for increased acidity • Binding Free Molecules or Atoms e.g. drugs for heavy metal poisoning, infliximab (anti-TNF) HOW DO DRUGS WORK BY UNCONVENTIONAL MECHANISMS OF ACTION (Continued)? •Being Nutrients e.g. vitamins, minerals • Exerting Actions Due to Physical Properties e.g. mannitol (osmotic diuretic), laxatives • Working Via an Antisense Action e.g. fomivirsen for CMV retininitis in AIDS • Being Antigens e.g. vaccines •Having Unknown Mechanisms of Action e.g. general anesthetics ARE DRUGS THAT ANTAGONIZE CELL SURFACE RECEPTORS CLINICALLY USEFUL? Some important examples: • Angiotensin Receptor Blockers (ARBs) for high blood pressure, heart failure, chronic renal insufficiency (losartan [Cozaar®]; valsartan [Diovan®]) • Beta-Adrenoceptor Blockers for angina, myocardial infarction, heart failure, high blood pressure, performance anxiety (propranolol [Inderal®]; atenolol [Tenormin®])

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