Introduction to Pharmacology Lecture 1 PDF

Introduction to Pharmacology Pharmacokinetic 1 Dr. Nesreen Elgayar  Pharmacodynamic Body Drug Pharmacokinetic  Outlines Introduction about Pharmacology. Pharmacokinetics. Absorption of Drug. Factors Affecting Absorption...

Introduction to Pharmacology Pharmacokinetic 1 Dr. Nesreen Elgayar  Pharmacodynamic Body Drug Pharmacokinetic  Outlines Introduction about Pharmacology. Pharmacokinetics. Absorption of Drug. Factors Affecting Absorption of Drug. Drug Properties. Drug Formulation. Pharmacokinetics  Pharmacokinetics It is a quantitative study of drug Absorption Distribution ADME Metabolism Excretion  Absorption Absorption is the passage of a drug from site of administration to reach Blood  Factors affecting Drug Absorption ? I- Drug Factors Drug properties Drug Formulation II- Patient Factors  I. Drug properties MW ↓ MW → ↑ Absorption ↑ MW → ↓ Absorption e.g. procaine penicillin (PP) Lipophilicity  Solubility Non-ionized drug is lipid-soluble and diffusible. Ionized drug is water-soluble and non-diffusible..Ionization is pH-dependent  Solubility In solution, Drugs are ionized to different degrees depending on : -pH of the solution (Body fluid) and -pKa of the drug.  pKa (Dissociation or Ionization Constant) It is the pH of the medium at which drug (PH=PKa) 50% 50% Ionized Nonionized  Acidic Drug Basic Drug Acidic Basic Ionization Hydrophilic Nonionized Execreted Nonionized Lipid soluble( )Absorped )Lipid soluble( Absorped  Clinical Significance of pKa 1. GIT Aspirin: (weak acid; pKa 3.5) is non-ionized in stomach → crosses cell membrane → gastric mucosal cells → trapped inside these cells (aspirin trap) → death of cells → peptic ulceration  Clinical Significance of pKa 2. Kidney Drug ionization →↑ renal excretion. So…. Alkalinization of urine in Acidic drug Toxicity e.g. Aspirin Acidification of urine in Basic drug Toxicity e.g. Amphetamine  II. Drug Formulation Active Drug + Vehicle Vehicle: Aqueous (cream) > absorbable Oily (ointment)  Tablet Disintegration Particles Dissolution Molecules + Ions Fragments Absorbed.Slow release tab. & sustained release cap (Spansules) Long Acting Less Frequent administration Less Adverse Effects (Low Good Compliance peak Level)  How to prolong Action of Drug? ↑ MW Use Oily Prep. Use Spansules Add VC to local anesthesia