lec 3 - Introductory Pharmacology Chemical properties of...

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Introductory Pharmacology Chemical properties of Relevance to Pharmacology Lecture 3: April 3, 2009 Previously: Partition coefficient – importance of lipophilicity of drugs for entry into organisms Importance of ionization for drug uptake – Henderson Hasselbach Equation Biological pHs Fick’s diffusional flux relationship Nonionized molecules cross membrane barriers more readily than ionized molecules
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pKa examples of drugs weak acids or weak bases Weak acids: Weak bases: Aspirin – 3.5 Atropine 9.7 Ibuprofen 4.4, 5.2 Cocaine 8.5 Pentobarbital 8.1 Codeine 7.9 Phenobarbital 7.4 Ephedrine 9.4 Salicylic acid 3.0 Ergotamine 6.3 Warfarin 5.0 Nicotine 7.9, 3.1 Physostigmine 7.9, 1.8 Strychnine 8.0, 2.3 Diazepam 3.0 From prior Lecture DO NOT MEMORIZE!
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Examples of weak acids–ASA Examples of weak bases Norepinephrine–primary amine p Ka = 8.6 Epinephrine – secondary amine p Ka = 8.7 Cocaine–tertiary amine p Ka = 8.5 Neostigmine – quaternary amine 1 2 3 4 From prior Lecture DO NOT MEMORIZE!
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PROBLEM EXAMPLE #1 For weak acids: LOG { [HA] / [A ] } = pK a –pH LOG {nonionized / ionized} = pK a –pH Warfarin has a pK a = 5.0 In stomach, pH ~ 2, LOG {non/ion} = 5.0–2.0 = 3
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This note was uploaded on 09/02/2009 for the course CHEM 118 taught by Professor Staff during the Spring '08 term at UCSD.

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lec 3 - Introductory Pharmacology Chemical properties of...

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