2. Faculty of Pharmacy Department of Pharmacology pharmacology General Pharmacology 3rd year pharmacy students By “Dr. Shimaa Elshazly”
3. What is pharmacology? The term pharmacology comes from the Greek words: •Pharmakon- drug or medicine •Logos- the truth about or a rational discussion …………Truth about medicine • Pharmacology is the study of how drugs exert their effects on living systems. • More specifically it is the study of the interactions between a living organism and drugs that alter normal biochemical function.
4. History of Pharmacology Early pharmacology focused on natural substances, mainly plant extracts.
15. Drug Absorption • Absorption is the movement of a drug from its site of application into the blood or lymphatic system without being chemically altered • Mathematically it is define in terms of Bioavailability (Rate and extent of absorption).
16. Bioavailability Definition: Rate and extent of absorption i.e. Ka (Absorption constant)………. Rate of absorption. Area under curve (AUC)………. extent of absorption. • for i.v.: 100% • for non i.v.: ranges from 0-100% e.g. lidocaine bioavailability is 35% due to destruction in gastric acid and liver metabolism
17. Process of Absorption In order for a drug to be absorbed, it must be able to pass through cell membranes (which is a lipid barrier) • Lipid soluble drugs would be ideal to pass through the membrane easily. • Drugs can be absorbed by 4 main ways : 1. Simple diffusion = passive diffusion. 2. Active transport. 3. Facilitated diffusion. 4. Pinocytosis (Endocytosis).
28. Simple diffusion Drugs exist in two forms ionized (water soluble) & nonionized forms (lipid soluble) in equilibrium. Drug ionized + nonionized Only nonionized form is absorbable.
52. Phagocytosis (Endocytosis & Exocytosis) Endocytosis: uptake of membrane-bound particles. Exocytosis: expulsion of membrane-bound particles. High molecular weight drugs or Highly lipid insoluble drugs
53. Factors which influence the rate of absorption: – Routes of drug administration – The physicochemical properties of the drug – Dosage forms – Circulation at the site of absorption – Concentration of the drug
54. Routes of drug administration Enteral via gastrointestinal tract (GIT). Oral Sublingual Rectal Parenteral administration = injections. Topical application Inhalation
91. Factor affecting absorption…… pH and lipid solubility: Most drugs are either weak acids or weak bases and can exist in either the ionised (less lipid soluble) or unionised (more lipid soluble) form depending on the pH of the surrounding environment. REMEMBER THAT A DRUG IS ABSORBED BETTER IN THE UNIONISED FORM (Lipophillic drug can cross cell membrane)
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93. In this form, it can enter the cells of the stomach lining (pH=7.4) where it is ionized and, in this form, it cannot leave the cell.
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96. A syrup has fast rate of absorption as compare to tablet
