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Let’s learn PHARMACOLOGY

Welcome Friends. Let’s learn PHARMACOLOGY. Greek Word. Pharmacon. Logos. Drug. Science. PHARMACOLOGY. Science of drugs- dealing with the study of Desirable and Undesirable effects. Pharmacology is the study of drugs and their actions on the body. What is PHARMACOLOGY ?.

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Let’s learn PHARMACOLOGY

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  1. Welcome Friends Let’s learn PHARMACOLOGY

  2. Greek Word Pharmacon Logos Drug Science PHARMACOLOGY Science of drugs- dealing with the study of Desirable and Undesirable effects.

  3. Pharmacology is the study of drugs and their actions on the body

  4. What is PHARMACOLOGY ? Pharmacokinetics Pharmacodynamics What the body does to drug What the drug does to body Pharmacology PharmacotherapeuticsPharmacy The study of the use of drugsPreparing suitable dosage forms Toxicology

  5. PHARMACY • It is the science of: • Identification • Selection • Preservation • Standardization • Compounding, and • Dispensing of medicinal substances

  6. PHARMACOPOEIA • It is an official code containing a selected list of the established drugs and medicinal preparations with descriptions of their physical properties and tests for their identity, purity and potency. e.g. IP, BP, USP, etc. • IP: Indian Pharmacopoeia • BP: British Pharmacopoeia • USP: United states Pharmacopoeia

  7. DRUG “ Drug is any substance or product that is used or is intended to be used to modify physiological systems or pathological states for the benefit of the recipient .”

  8. “Poisons in small doses are the best medicines; and useful medicines in too large doses are poisonous” William Withering 1789

  9. DRUG NAMES • Chemical…states its chemical composition and molecular structure. • Generic…usually suggested by the manufacturer. • Official…as listed in the Pharmacopoeia. (I.P., B.P., U.S.P.) • Brand…the trade or proprietary name.

  10. DRUG NAMES

  11. THE NATURE AND SOURCES OF DRUGS • Mineral • Animal • Plant • Synthetic • Micro-organisms • Drugs produced by genetic engineering • Liquid paraffin, magnesium sulfate, etc • Insulin, Thyroid, etc. • Morphine, Quinine etc • Aspirin, Sulfonamides, etc. • Penicillin & other antibiotics. • Human insulin, human growth, hormone etc.

  12. DRUG DEVELOPMENT PROCESS Chemistry Synthesis & Purification Formulation Animal Pharmacology Animal Toxicity (Short / Long term) Studies in Humans Drug Authorities Market

  13. DRUG DEVELOPMENT PROCESS

  14. DOSE Vs DOSAGE • Dose: The quantity of drug administered at one time • 500mg of Paracetamol • Dosage: The amount of the drug that should be given over time • 500 mg Paracetamol TID for 3 days

  15. DRUG DOSAGE FORMS Tablets Capsule Aerosol Injection Suspension Infusion Cream Solution

  16. ROUTES OF DRUG ADMINISTRATION How the drug is given Parenteral (injectable) Topical Enteral • Intranasal • Inhalation • Intravaginal • Oral • Sublingual • Rectal 1. Intravenous 2. Intramuscular 3. Subcutaneous

  17. PHARMACOKINETICS • The study of what the body does to the drug • It is the study of absorption, distribution, metabolism and excretion(ADME) of drugs • “Fate of drug”

  18. PHARMACOKINETICS • Absorption • How the drug is moved into blood stream from the site of administration ? • Distribution • How much drug is moved to various body tissues / organs ? Depends on blood flow through tissue • Metabolism • How the drug is altered – broken down ? • Excretion • How much of the drug is removed from the body ?

  19. ABSORPTION Site of Administration Vascular System DRUG BIOLOGICAL BARRIER

  20. Drug Absorption of Various Dosage Forms • Oral Preparations • Liquids, elixirs, syrups FastestSuspension solutions êPowders êCapsules êTablets êCoated tablets êEnteric-coated tablets Slowest

  21. Blood level Time IV Route What would the graph of blood level against time look like?

  22. Blood level Time ORAL Route What would the graph of blood level against time look like?

  23. What is happening in these two phases? ? ? Blood level Time

  24. Absorption and Distribution Metabolism and Excretion Blood level Time

  25. BIOAVAILABILITY • Bioavailability is a fraction of administered dose of a drugthat reaches the systemic circulationin theunchanged form. • Bioavailability of IV route :100 %

  26. BIOAVAILABILITY Destroyed in gut Not absorbed Destroyed by gut wall Destroyed by liver to systemic circulation Dose

  27. BIOAVAILABILITY • Factors influencing bioavailability • Dosage forms • Chemical form • Dissolution & Absorption of drug • Route of administration • Presence of food/drugs in GI tract • First pass effect • Extent of drug metabolism before reaching systemic circulation

  28. MSC MEC

  29. Concept of Critical Threshold • MEC (Minimum Effective Concentration): The minimum level of drug concentration needed for the desired therapeutic effect to be present. • MSC (Maximum Safe Concentration): The maximum level of drug concentration above which toxic effects occurs. • OR • MTC (Minimum Toxic Concentration): The minimum level of drug concentration that produces toxic effects.

  30. Maximal Effect: Greatest response that can be produced by a drug, above which no further response can be created (sometimes called “peak effect”) • Onset: How long before a drug is able to exert a therapeutic effect • Duration: How long a drug effect lasts

  31. DRUG HALF-LIFE (t1/2 ) • Half life is the time required to reduce the plasma concentration to 50% of its original value • Will determine dosing requirements / how long a drug will remain in the body • Used in determining dosing interval • Goal - Plateau

  32. DRUG HALF-LIFE (t1/2 ) Half-life is the time taken for the concentration of drug in blood to fall by a half Half-life is 2 hrs

  33. DRUG HALF-LIFE (t1/2 ) • 1 t1/2 -50 % drug is eliminated • 2t1/2 - 50+25 (75 %) drug is eliminated • 3 t1/2 - 50+25 +12.5 (87.5 %) drug is eliminated • 4 t1/2 - 50+25 +12.5+6.25 (93.7 %) drug is eliminated • Thus, nearly complete drug elimination occurs in 4-5 half lives.

  34. DRUG HALF-LIFE (t1/2 ) 50 25 12.5 6.25 3.12 1.56

  35. Cmax & Tmax Cmax Concentration Tmax Time • Cmax - Maximum conc. achieved in the blood • Tmax - Time taken to attain maximum conc.

  36. AUC (Area Under Curve) AUC • AUC is the area under the plot of plasma concentration of drug against time after drug administration.

  37. DISTRIBUTION Distribution is a branch of pharmacokinetics which describes the reversible transfer of drug from one location to another within the body.

  38. DISTRIBUTION Locus of action“receptors”Bound Free TissuereservoirsBound Free Systemiccirculation Excretion Absorption Free drug Excretion Bound drug Metabolites Biotransformation

  39. Many drugs bound to circulating plasma proteins such as albumin, lipoproteins, glycoprotein, globulins etc. Free form Pharmacologically active Bound form Pharmacologically inactive Receptor Site Protein-bound drug Free Drug Plasma- Protein Binding

  40. Dosing Interval - How often the drug should be given Loading dose – Which puts the plasma concentration in the therapeutic range Maintenance dose - Routine smaller doses to maintain the steady state (Plateau) Dosing

  41. Metabolism = change / biotransformation The conversion from one chemical form to another Site of drug biotransformation Liver - cytochrome P450 pathways OR microsomal P450 pathways are used to metabolize most agents Enzymatic alteration of drug structure Effect of metabolism 80% of drugs become inactive Inactive drug becomes active: Prodrug Some drugs do not get metabolised at all METABOLISM

  42. Majority of drugs are metabolized in liver by enzymes – Cytochrome P 450 Drugs may induce (activate) or inhibit these enzymes METABOLISM Drug – Drug interactions

  43. First Pass Metabolism The first-pass metabolism (also known as first-pass effect or presystemic metabolism) is a phenomenon of drug metabolism whereby the concentration of a drug is greatly reduced before it reaches the systemic circulation.

  44. First Pass Metabolism Hepatic portal system Swallowed Drug Digestive system Rest of the body Liver

  45. First Pass Metabolism • Systems that affect the first pass effect of the drug, • Enzymes of the gastro intestinal lumen • Gut wall enzyme • Bacterial enzymes • Hepatic enzymes

  46. First Pass Metabolism • Effect of first pass metabolism • Part of administered dose made inactive • ↓ bioavailability • Drug converted into its active form • Nitroglycerin when given orally • Totally inactivated in the liver • 100% first pass effect • Always given sublingually

  47. Administered in an inactive form After administration converted into their active form usually in liver Designed to improve bioavailability Examples Enalapril – Enalaprilate Ramipril - Ramiprilate Prodrug

  48. Factors affecting metabolism : Age – Children / Elderly Disease condition – e.g. Liver disease Induction of drug metabolizing enzymes First-pass effect – Nitroglycerin Competition between drugs Genetics Environment e.g. Smoking METABOLISM

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