MODERN MEDICINAL CHEMISTRY

Transcription

1 MODERN MEDICINAL CHEMISTRY JOHN B. TAYLOR, B.SC.,D.I.C.,PI..D., Senior Vice President, Central Research, Rhone-Poulenc Rorer, Dagenham Research Centre, Essex and PETER D. KENNEWELL, B.A.,M.A.,Ph.D., Scientific Adjoint to the Immunology Group, Roussel Laboratories Limited, Swindon, Wiltshire ELLIS IIORWOOD NEW YORK LONDON TORONTO SYDNEY TOKYO SINGAPORE

2 Table of contents Authors' preface 1 Introduction 1.1 Definitions Pharmacology Clinical pharmacology.1.3 Molecular pharmacology.1.4 Microbiology.1.5 Biochemistry.1.6 Physiology and medicine.1.7 Pharmacy.1.8 Molecular biology 1.2 ^rug development 2.\ Historical development.2.2 Selectivity.2.3 Enantioselectivity 1.3 ' The scene today Classification of drugs CNS or psychopharmaceutical agents Pharmacodynamic agents Chemotherapeutic agents Metabolic diseases and endocrine functions Industry'commercial aspects The evolution of the pharmaceutical industry The industry today Products Research The development of drugs Achievements _s

3 vi Table of contents Patents Biotechnology Industry-government interactions The future Major processes of drug action The pharmaceutical phase The pharmacokinetic phase The pharmacodynamic phase 48 2 The pharmaceutical phase Introduction to biopharmaceutics Physicochemical principles Crystallinity and polymorphism in drug formulation Particle size of the drug substance Formulation science Dosage forms Liquid formulations Solutions Suspensions Emulsions Semisolid formulations Creams Ointments Gels Solid formulations Tablets Capsules Moulded products Routes of administration of medicines Introduction Oral Drugs acting locally within the GI tract Drugs acting systemically Parenteral administration Intravenous Other parenteral routes Rectal administration Vaginal and uterine administration Nasal Buccal and sublingual administration Transdermal administration Pulmonary Summary ^ 2.5 Controlled release dosage forms Introduction 67 35

4 Table of contents vii GI tract delivery system Rationale Matrix devices Gastric retention devices Bioadhesives Transdermal delivery systems Introduction Skin structure and function Advantages and disadvantages of transdermal 69 drug delivery Examples of drug applications 71 3 Pharmacokinetic phase Introduction Absorption processes Introduction Gastrointestinal absorption Physiology of the GI tract Factors affecting absorption Rectal absorption Transdermal absorption Intranasal absorption Buccal absorption Vaginal absorption Lung absorption Distribution General principles Affinity Physiological factors affecting affinity The distribution compartment Critical factors affecting distribution Blood flow Protein binding Membrane transfer Distributions of specific interest Central nervous system The bacterial membrane Clearance General principles Physiological and kinetic aspects Pharmacokinetic considerations Critical factors affecting hepatic clearance Physiological aspects Metabolic and biliary clearance Critical factors affecting renal clearance 97

5 viii Table of contents Physiological factors ^ Physicochemical factors ^ 3.5 Sites of drug metabolism Liver Gastrointestinal tract " Kidney " Lung " Other tissues '"' 3.6 Biotransformation Introduction XG Prodrugs Hard and soft drugs w ~ Bioactivation Reactive metabolites I Sites of action l Metabolic pathways '^ Introduction Phase I or functionalisation reactions Oxidations Reductions n Hydrolysis II Phase II or conjugation reactions 1 ' Glucuronic acid conjugation HO Glutathione conjugation 1'' Amino acid conjugation I' Acetylation Methylation Suiphation The pharmacodynamic phase Introduction Cell structures The cell membrane Membrane lipids Membrane proteins Membrane carbohydrates Receptor theories 125 4> Types of hinding in drug receptor interactions Covafent bonds Electrostatic interaction Charge redistribution Van der Waals'forces Entropy-based forces The use of radio-labelled ligands Isolation of receptors 138

6 Table of contents ix Separation of specific receptors from membranes Purification of target protein The use of molecular biology Primary and secondary messengers Primary messengers The neuron Electrical transmission in neurons The organisation of the nervous system Neurotransmitters Other transmitters Neuromodulators Secondary messengers Intracellular proteinaceous receptors DNA as a receptor Enzymes Definitions Isoenzymes and isofunctional enzymes Enzyme catalysis Kinetics Graphical representation The nature of enzymatic catalysis Cooperativity and allosterism Enzyme inhibition Types of inhibition Reversible inhibition Reversible inhibitors: transition state analogues Reversible inhibitors: multisubstrate analogues Irreversible enzyme inhibitors Irreversible enzyme inhibitors: active site directed inhibitors Irreversible enzyme inhibitors: 188 mechanism-based inhibitors Resistance and tolerance Specific enzymes Oxygenascs Reductases Hydrolascs Peptidascs The enzymes in cholesterol synthesis Cell wall biosynthesis Enzymes affecting DNA replication Catalytic antibodies RNA as enzymes 201

7 x Table of contents 5 Drug discovery processes Introduction ZT 5.2 Sources of lead structures 2W Clinical and pharmacological side effects Random screening Natural source of drugs Plants Microbes 2 " Marine sources Macromolecular targets for drug design Proteins as targets Molecular biology and the production of proteins Determination of protein structure X-ray crystallography Nuclear magnetic resonance spectroscopy The prediction of secondary and tertiary 232 structures of proteins from their amino acid sequences DNA as a macromolecular target "Anti-sense" oligonucleotides Computational chemistry Quantum mechanics Molecular mechanics Molecular dynamics Computer graphics Modelling drug-receptor interactions Drug design methods Receptor fitting Haemoglobin Thyroid hormone-prealbumin interactions Inhibition of phospholipase A The inhibition of dihydrofolate reductase Grid Automated site-directed drug design Applications of drug design techniques Optimisation of lead structures Historical Linear free energy relationships Partition coefficients Electronic effects Steric effects Use of the Hansch approach Topliss approach Batch selection methods The Free Wilson method 275

8 Table of contents xi Selected pattern recognition techniques Statistical methods Distance mapping 279 References 281 Selected Bibliography 284 Index 286