Pharmacodynamics.pptx

PHARMACOLOGY IS CHALLENGING SUBJECT TO TEACH AND UNDERSTAND ALSO .....THEIR INTERESTING PART IS TO LEARN ABOUT PHARMACODYNAMICS

1. Pharmacodynamics BY ASAWE TEJASWINI L DEPARTMENT OF PHARMACOLOGY ASSIASTANT PROFESSOR SIDHHIS INSTITUTE OF PHARMACY THANE

2. Pharmacodynamics ( how drugs work on body ) Pharmacodynamics is the study of the response of the body to the drug. Pharmacodynamics is affected by receptor binding and sensitivity , post receptor effects and chemical interaction. Disorders that affect pharmacodynamics response include genetic mutation, malnutrition, , Parkinson's disease and some forms insulin resistance diabetes mellitus.

3. Mechanism of drug action A drug may produce its effects through various mechanism: A- Physical mechanism – When drug does not produce chemical reaction or change in body cell and the effect is only physical is called physical mechanism. These includes: 1.Local application -drugs are applied on the external surface of skin. counter irritant used to mask the pain sensation. 2.Antacid - antacids are drug used which neutralize the acid in stomach 3.Liquid paraffin – it is used to relieve constipation . 4.Astringents -  able to stop a cut from bleeding. 5.Activated charcoal- Activated charcoal used to neutralize various poison .

4. B) Chemical Mechanism – In Chemical Mechanism drug acts by producing chemical reactions in the body. These includes : 1.Chemically acting antacids – Chemically acting antacids react chemically with HCL of stomach , causing neutralization. 2.Chelating agent – Chelating agents are the drug used to treat poisoning with various metal.

5. C) Drug Receptor Interaction – There are 3 forms of binding to receptors 1.Agonist 2.Antagonist 3.Partial Agonist 1.Agonist – Most of drug bind to receptor and produces maximum effect is called agonist. 2.Antagonist – The drug work in the opposite to agonist is called antagonist. Antagonist can only produce effect by blocking access of neurotransmitter (agonist) to the receptor. 3.Partial Agonist A drug which bind and less than maximal effect is called partial agonist.

6. receptors Receptors are macromolecules, proteins in nature which are target sites of drug. Drugs have to bind receptors to produce effect. Receptors are located mostly on the cell membrane Types of Receptor – 1. Ion Channel Receptors 2.G- Protein Linked Receptor 3.Enzyme Receptor 4.Nuclear Receptor

7. 1.Ion Channel Receptors – These receptors have a channel through ions can move inside and outside the cells. They are located on the cell surface. They enclose ion selective channels for sodium , potassium , calcium and chloride. When an agonist is bound to these receptors they convey signals. E.g. Muscarinic , Noradrenergic receptor

8. 2. G- Protein coupled receptor – These are largest class of receptors. They are located on the cell membrane. G- Protein is a connecting link between receptor and effectors system like enzymes , carrier molecules etc They link with GTP (guanosine triphosphate) and GDP (Guanosine diphosphate) It is used as a source of energy for protein synthesis and gluconeogenesis. 

9. 3.Enzyme receptor – These receptors are cytoplasmic receptors. Their action involves enzymatic activation by phosphorylation. Phosphorylation is the addition of a phosphoryl (PO 3 ) group to a molecule. Ex. Insulin receptor, Cytokine receptor   Cytokine receptor are cell-surface glycoprotein's bind specifically to cytokines and transduce their signals. The receptor for insulin is a large protein that binds to insulin and passes its message into the cell. 4.Nuclear receptor – Present either in cytoplasm or nucleus of the cell. Vit A, corticosteroids etc act through these response receptors.

10. Combined effect of drug When two or more drugs are given simultaneously or directly after each . There are different types of effects produced when two or more drugs are combined. 1.No interference with each others effects. 2.May oppose each others action (antagonism) 3. May produce similar actions on the same organ(synergism ).

11. Factors modifying drug effect Following factor influencing the drug response 1. Drugs factor – Physical properties of drug such physical state, crystal structure, size of particles of drug determines the ability of absorption and drug effect. Drug and dosage form such as solid , liquid and semisolid. Small dose may show less effect and high dose may cause unconsciousness , coma or death. Repeated administration of drug produce tolerance .

12. 2.physiological factor – Age - The adult dose is for people between 18- 60 years of age. The tissue of infant and child are highly sensitive to large number of drug. Geriatric age group (above 60 yr) requires special consideration like reduced body weight , reduced body fat, reduced renal and hepatic function . Body weight – dose is given per kg body weight. Allergy – may cause skin rashes , fall of BP. Food - drugs are better absorbed in empty stomach. To prevent gastric irritation most drugs taken after or between foods.

13. 3.Pathological factors ( A)Liver Diseases cause individual variation in drug response – ↓ Plasma protein binding for warfarin, tolbutamide → leads adverse effects. – ↓ Hepatic blood flow → ↓ clearance of morphine-propanolol may affected – Damage liver microsomal enzymes may lead to toxic level of Diazepam-rifampicin-theophylline. (B) Renal Disease – ↓ GFR. – ↓ tubular function. – ↓ Plasma albumin ↓excretion of digoxin-lithium-gentamycin-penicillin. (C) Malnutrition – ↓ plasma protein binding of drugs. – ↓ amount of microsomal enzymes. – ↑ Increases portion of free, unbound drug e.g. warfarin

14. 4 . . Genetic Factors Genetic abnormality influence the dose of drug and response to drugs. Idiosyncrasy – Idiosyncrasy is abnormal genetic response to the drug . It is usually harmful. These type of response seen in small portion of population. Ex. Aplastic anaemia ( bone marrow cannot make enough new blood cells ) due to chloramphenicol antibiotic used in typhoid and cholera.

15. 5.Environmental factor Routes of administration – Some drugs are incompletely absorbed after oral intake , when given intravenously. Time of administration- Hypnotic acts better when administered at night and smaller doses are required. Effect of climate – Metabolism of drug is low in hot and humid climate Purgative acts better in summer while diuretics act better in winters. Preparation of drug Drugs in solid forms disintegrate slowly .onset of action is rapid when drug is given in liquid form