Pharmacodynamics PPT

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Pharmacodynamics by vijayfarmac

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Pharmacodynamics PPT

  1. 1. PHARMACODYNAMICS
  2. 2. • In Greek Pharmacon = Drug Dynamics = Action/Power It covers all the aspects relating to “What a drug does to the body” Mechanism of action
  3. 3. • Action: How and Where the effect is produced is called as Action. • Effect: The type of response producing by drug.
  4. 4. Site of Drug Action • Where: 1. Extra cellular 2. Cellular 3. Intracellular
  5. 5. Types of Drug Action EFFECT (Type of responses):- 1.Stimulation 2.Inhibition/Depression 3.Replacement 4.Irritation 5.Cytotoxic
  6. 6. Mechanism of Action of Drugs • Drug act either by receptor or by non receptor or by targeting specific genetic changes. Majority of drugs acts by (HOW) Receptor mediated Non receptor mediated
  7. 7. Receptor Mediated action • Drug produce their effect through interacting with some chemical compartment of living organism c/s Receptor. • Receptors are macromolecules • Most are proteins • Present either on the cell surface, cytoplasm or in the nucleus
  8. 8. Receptor Functions : Two essential functions • 1. Recognization of specific ligand molecule (Ligand binding domain) • 2. Transduction of signal into response (Effector domain) Ligand binding domain Transduction of signal into response
  9. 9. Drug(D) +Receptor® Drug receptor complex Response Drug receptor interaction:- 1. Selectivity:- Degree of complimentary co relation between drug and receptor. Ex:- Adrenaline Selectivity for α, ß Receptor 2. Affinity:- Ability of drug to get bound to the receptor. 3. Intrinsic activity (IA) or Efficacy:- Ability of drug to produce a pharmacological response after making the drug receptor complex.
  10. 10. Drug classification (on the basis of affinity & efficacy)
  11. 11. Response No response
  12. 12. • Partial agonist :These drug have full affinity to receptor but with low intrinsic activity (IA=0 to 1). • These are only partly as effective as agonist (Affinity is lesser when comparison to agonist) Ex: Pindolol, Pentazocine
  13. 13. • Inverse agonist: These have full affinity towards the receptor but intrinsic activity is zero to -1 i.e., produces effect is just opposite to that of agonist. Ex:- ß-Carboline is inverse agonist for Benzodiazepines receptors.
  14. 14. Receptor families Four types of receptors families 1. Ligand-gated ion channels (inotropic receptors) 2.G-protien coupled receptor (Metabotropic receptors) 3. Enzymatic receptors (tyrosinekinase) 4.Receptor regulating gene expression (transcription factors/ Steroid )
  15. 15. Characteristics of receptor families Ligand gated G-protein coupled Enzymatic Nuclear Location Membrane Membrane Membrane Intracellular Effector Ion channel Ion Channel or enzyme Enzyme Gene coupling Direct G-protein Direct Via DNA Example Nicotinic Muscarinic Insulin Steroid , hormone
  16. 16. Signal transduction mechanism • Ion gated receptors:- Localized on cell membrane and coupled directly to an ion channel. Receptor Agonist Hyper polarization or depolarization Receptor Blocker Permeation of ion is blocked Cellular effect No cellular effect Io n Na+2
  17. 17. • Ex: Nicotinic cholinergic receptor
  18. 18. G-protein coupled receptors • Membrane bound, which are coupled to effector system through GTP binding proteins called as G-proteins Bound to inner face of plasma membrane (2nd messenger)
  19. 19. Varieties of G-protein G-protein Receptor for Signaling pathway/ Effector Gs ß adrenegic, H,5HT,Glucagon AC— cAMP Gi1,2,3 α2 adrenergic, Ach, AC— cAMP, Open K+ Gq Ach Phospholipase-C, IP3’cytoplasmic Ca+2 Go Neurotransmitters in brain Not yet clear
  20. 20. G-protein effector systems • 1.Adenylase cyclase : cAMP system • 2.Phospholipase –C: Inositol phosphate system • 3. Ion channels
  21. 21. cAMP system
  22. 22. Phospholipase-C system
  23. 23. Ion channel regulation • G-protein coupled receptors can control the functioning of ion channel by don't involving any second messenger • Ex:- In cardiac muscle
  24. 24. • These receptor are directly linked tyrosine kinase. • Receptor binding domain present in extra cellular site. • Produce conformational changes in intra cellular Ex:- Insulin receptors Enzymatic receptors
  25. 25. Enzymatic receptors Extra cellular receptor binding domain Intra cellular changes
  26. 26. Receptor regulating gene expression (transcription factors) Unfolds the receptor and expose normally masked DNA binding site Increase RNA polymerase activity
  27. 27. Receptor regulation theory • Receptors are in dynamic state. • The affinity of the response to drugs is not fixed. It alters according to situation. • Receptor down regulation: Prolonged use of agonist Receptor number and sensitivity Drug effect Ex: Chronic use of salbutamol down regulates ß2 adrenergic receptors.
  28. 28. • Receptor up regulation: Prolonged use of antagonist Receptor number and sensitivity Drug effect • Ex:- propranolol is stopped after prolong use, produce withdrawal symptoms. Rise BP, induce of angina.
  29. 29. Agonist: Both the high affinity as well as intrinsic activity (IA=1) These drug trigger the maximal biological response or mimic effect of the endogenous substance. Ex:- Methacholine is a cholinomimetic drug which mimics the effect of Ach on cholinergic receptors.
  30. 30. Types of agonism • Summation :- Two drugs eliciting same response, but with different mechanism and their combined effect is equal to their summation. (1+1=2) Aspirin Codiene PG Opiods receptor Analgesic+ Analgesic+ ++
  31. 31. Types of agonism • Additive: combined effect of two drugs acting by same mechanism Aspirin PG PG Analgesic+ Analgesic+ + +
  32. 32. • Synergism (Supra additive):- (1+1=3) The combined effect of two drug effect is higher than either individual effect. Ex:- 1.Sulfamethaxazole+ Trimethoprim 2. Levodopa + Carbidopa.
  33. 33. Types of antagonism Antagonism: Effect of two drugs is less than sum of the effects of the individual drugs. 1. Chemical antagonism Ex: -heparin(-ve) protamine +ve, Chelating agents 1. Physiological /Functional antagonism 2. Pharmacokinetic antagonism 3. Pharmacological antagonism I. Competitive ( Reversible) II. Non competitive (Irreversible)
  34. 34. Pharmacokinetic antagonism • One drug affects the absorption, metabolism or excretion of other drug and reduce their effect. Ex:-Warfarin in presence of phenobarbitone, warfarin metabolism is increased, it effect is reduced.
  35. 35. Pharmacological antagonism • Pharmacodynamic antagonism between two drugs acting at same receptors. • Two important mechanism according to which these antagonists »1.Reversible(Competitive) »2.Irreversible(Non)
  36. 36. Reversible antagonism (Competitive antagonism) • These inhibition is commonly observed with antagonists that bind reversibly to the same receptor site as that of an agonist. • These type inhibition can be overcome increasing the concentration of agonist • Ex:- Atropine is a competitive antagonist of Ach.
  37. 37. Irreversible Antagonism • It occurs when the antagonist dissociates very slow or not at all from the receptors result that no change when the agonist applied. • Antagonist effect cannot be overcome even after increasing the concentration of agonist
  38. 38. Non receptor mediated action • All drugs action are not mediated by receptors. Some of drugs may act through chemical action or physical action or other modes. »Chemical action »Physical action (Astringents, sucralfate) »False incorporation (PABA) »Being protoplasmic action (antiseptics) »Formation of antibody (Vaccines) »Targeting specific genetic changes.
  39. 39. Dose • It is the required amount of drug in weight, volumes, moles or IU to provide a desired effect. • In clinical it is called as Therapeutic dose • In experimental purpose it is called as effective dose. • The therapeutic dose varies from person to person
  40. 40. Single dose: 1.Piperazine (4-5g) is sufficient to eradicate round worm. 2.Single IM dose of 250mg of ceftriaxone to treat gonorrhoea. Daily dose: It is the quantity of a drug to be administered in 24hr, all at once or equally divided dose. 1.10mg of cetrizine (all at once) is sufficient to relive allergic reactions. 2.Erythromycin is 1g per day to be given in 4 equally divided dose (i.e., 250mg every 6 hr)
  41. 41. • Total dose: It is the maximum quantity of the drug that is needed the complete course of the therapy. Ex:- procaine penicillin early syphilis is 6 million unit  given as 0.6 million units per day for 10days. Loading dose:- It is the large dose of drug to be given initially to provide the effective plasma concentration rapidly. The drugs having high Vd of distribution. Chloroquine in Malaria – 600 mg Stat 300mg after 8 hours 300 mg after 2 days.
  42. 42. Maintenance dose:- Loading dose normally followed by maintenance dose. • Needed to maintain the steady state plasma concentration attained after giving the loading dose.
  43. 43. Therapeutic index: • Margin of safety • Depend upon factor of dose producing desirable effect  dose eliciting toxic effect. • TI should be more than one 50 50 ED LD indexcTherapeuti
  44. 44. Toxic Therapeutic window: Optimal therapeutic range of plasma concentrations at which most o the patients experience the desired effect. Therapeutic range Therapeutic window Sub optimal optimal
  45. 45. • Cyclosporine – 100-400ng/ml • Carbamazapine- 4-10µg/ml • Digoxin- 0.8-2ng/ml • Lithium- 0.8-1.4 mEq/L • Phenotoin – 10-20µg/ml • Qunindine- 2-6µg/ml
  46. 46. • Tolerance: Increased amount of drug required to produce initial pharmacological response. • Usually seen with alcohol, morphine, barbiturates, CNS active drugs • Reverse tolerance:- Same amount drug produces inc pharmacological response. • Cocaine, amphetamine  rats- inc. motor activity
  47. 47. Types of tolerances • Innate tolerance: Genetically lack of sensitivity to a drug. Ex: • Rabbits tolerate to atropine large doses • Chinese Castor oil • Negros  Mydriatic action of sympathomimetics • Eskimos high fatty diets
  48. 48. • Acquired tolerances: • Occurs due to repeated use of drug – Pharmacokinetic tolerances – Pharmacodynamic tolerance – Acute tolerance Pharmacokinetic tolerances:- Repetitive administration causes decrease their absorption or inc. its own metabolism Ex: Alcohol  dec. absorption Barbiturates Inc. own metabolism
  49. 49. • Pharmacodynamic tolerance • Down regulation of receptors • Impairment in signal transduction • Ex: Morphine, caffeine, nicotine. • Acute tolerance: Tachyphylaxis Acute development of tolerance after a rapid and repeated administration of a drug in shorter intervals • Ex; Ephedrine, tyramine
  50. 50. • Ex: Monday disease. • Nitroglycerine – Monday , Tuesday workers get headache, after they get tolerances. • After holiday (Sunday) they get again headache . • Cross tolerances: Cross tolerance among drugs belonging to same category. • MORPHINHEROIN NARCOTIC
  51. 51. FACTORS MODIFYING THE EFFECTS OF DRUGS
  52. 52.  Individuals differ both in the degree and the character of the response that a drug may elicit  Variation in response to the same dose of a drug between different patients and even in the same patient on different occasions.
  53. 53.  One or more of the following categories of differences among individuals are responsible for the variations in drug response:  Individuals differ in pharmacokinetic handling of drugs  Variation in number or state of receptors, coupling proteins or other components of response  Variation in neurogenic/ hormonal tone or concentrations of specific constituents
  54. 54.  These factors modify drug action either: a) Quantitatively  The plasma concentration and / or the drug action is increased or decreased b) Qualitatively  The type of response is altered, eg: drug allergy and idiosyncrasy
  55. 55.  The various factors are: 1. Body weight/size:  It influences the concentration of drug attained at the site of action  The average adult dose refers to individuals of medium built
  56. 56. • For exceptionally obese or lean individuals and for children dose may be calculated on body weight basis  BSA=BW(Kg)0.425 x Height(cm)0.725 x 0.007184 doseadultAveragex 70 (kg)BW doseIndividual doseadultAveragex 1.7 (m2)BSA doseIndividual
  57. 57. 2. Age: Infants and Children:  The dose of drug for children often calculated from the adult dose formula)sYoung'.........(doseadultx 12Age Age doseChild formula)sg'...(Dillindose......adultx 20 Age doseChild
  58. 58.  However, infants and children are have important physiological differences  Higher proportion of water  Lower plasma protein levels  More available drug  Immature liver/kidneys  Liver often metabolizes more slowly  Kidneys may excrete more slowly
  59. 59. Elders:  In elderly, renal function progressively declines (intact nephron loss) and drug doses have to be reduced  Chronic disease states  Decreased plasma protein binding  Slower metabolism  Slower excretion  Dietary deficiencies  Use of multiple medications  Lack of compliance
  60. 60. 3. Sex:  Females have smaller body size, and so require doses of drugs on the lower side of the dose range  They should not be given uterine stimulants during menstruation, quinine during pregnancy and sedatives during lactation
  61. 61. 4. Pregnancy:  Profound physiological changes which may affect drug responses:  GI motility reduced –delayed absorption of orally administered drugs  Plasma and ECF volume expands  Albumin level falls  Renal blood flow increases markedly  Hepatic microsomal enzyme induction
  62. 62. 5. Food:  Delays gastric emptying, delays absorption (ampicillin)  Calcium in milk –interferes with absorption of tetracyclines and iron by chelation  Protein malnutrition  Loss of BW  Reduced hepatic metabolizing capacity  Hypoproteinemia
  63. 63. 6. Species and race:  Rabbits resistant to atropine  Rat & mice are resistant to digitalis  In humans: blacks require higher Mongols require lower concentrations of atropine and ephedrine to dilate their pupil
  64. 64. 7. Route of drug administration:  I.V route dose smaller than oral route  Magnesium sulfate:  Orally –purgative  Parenterally –sedative  Locally –reduces inflammation
  65. 65. 8. Biorhythm: (Chronopharmacolgy)  Hypnotics –taken at night  Corticosteroid –taken at a single morning dose 9. Psychological state:  Efficacy of drugs can be effected by patients beliefs, attitudes and expectations  Particularly applicable to centrally acting drugs  In some patients inert drugs (placebo) may produce beneficial effects equivalent to the drug, and may induce sleep in insomnia
  66. 66. 10. Presence of diseases/pathological states:  Drug may aggravate underlying pathology  Hepatic disease may slow drug metabolism  Renal disease may slow drug elimination  Acid/base abnormalities may change drug absorption or elimination  Severe shock with vasoconstriction delays absorption of drugs from s.c. or i.m  Drug metabolism in:  Hyperthyroidism –enhanced  Hypothyroidism -diminished
  67. 67. 11. Cumulation:  Any drug will cumulate in the body if rate of administration is more than the rate of elimination  Eg: digitalis, heavy metals etc.
  68. 68. 12. Genetic factors:  Lack of specific enzymes  Lower metabolic rate  Acetylation  Plasma cholinesterase (Atypical pseudo cholinesterase)  G-6PD  Glucuronide conjugation
  69. 69. 13. Tolerance:  It means requirement of a higher dose of the drug to produce an effect, which is ordinarily produced by normal therapeutic dose of the drug  Drug tolerance may be:  Natural  Acquired  Cross tolerance  Tachyphylaxis (ephedrine, tyramine, nicotine)  Drug resistance
  70. 70. 14. Other drugs:  By interactions in many ways
  71. 71. Drug classification (on the basis of affinity & efficacy) Agonist: Both the high affinity as well as intrinsic activity (IA=1) These drug trigger the maximal biological response or mimic effect of the endogenous substance. Ex:- Methacholine is a cholinomimetic drug which mimics the effect of Ach on cholinergic receptors.
  72. 72. • Antagonist:- Which have only the affinity no intrinsic activity (IA=0). IA=0 so no pharmacological activity. • Rather these drug bind to the receptor and produce receptor blockade. • Atropine blocks the effects of Ach on the cholinergic muscarinic receptors.
  73. 73. cAMP system Some drugs, hormones or neurotransmitters produce their effect by increasing or decreasing the activity of adenylate cyclase and thus raising or lower cAMP with in the cell.
  74. 74. Stimulation • Some of drug act by increasing the activity of specialized cells. Ex: Catecholamines stimulate the heart and Heart rate, Force of contraction
  75. 75. Inhibition • Some drug act by decreasing the activity of specialized cells. Ex: Alcohol, Barbiturates, General anesthetic these drug depress the CNS system. Atropine inhibits Ach action.
  76. 76. Replacement • When there is a deficiency of endogenous substances, they can replaced by drugs. Ex: Insulin in Diabetes mellitus Throxine in cretinism and myxedema
  77. 77. Irritation • Certain drugs on topical application cause irritation of the skin and adjacent tissues. • These drugs are using for counter irritant. Ex: Eucalyptus oil, methyl salicylates (Used in sprains, joint pain, myalgia.
  78. 78. Cytotoxic • Treatment of infectious disease/cancer with drugs that are selectively toxic for infecting organism/cancer cells Ex: Anticancer drugs All Antibiotics
  79. 79. E Cam E* Gq PLC PIP2 DAG S Agonist HydrolysisActivation IP3 PKC ATP ADP Product Ca+2Cam Water soluble release Response Phospholipase-C system Hydrolysis PLC= Phospholipase-C PIP2 =Phosphotiydl inositol 4,5 di phosphate IP3 =Inositol tri phosphate DAG = Diacylglycerol E= Ezyme PKC = Phosphokinase -C
  80. 80. Extra cellular site of action 1.Antacids neutralizing gastric acidity. 2.Chelating agents forming complexes with heavy metals. 3.MgSo4 acting as purgative by retaining the fluid inside the lumen of intestine.
  81. 81. Cellular Site of Action 1.Ach on Nicotinic receptors of motor end plate, leading to contraction of skeletal muscle. 2.Effect of sympathomimetics on heart muscle and blood vessels.
  82. 82. Intracellular site of action -Folic acid synthesis inhibitors. Folic acid which is intracellular component essential for synthesis of proteins. Trimethoprim and sulfa drug interfere with synthesis.
  83. 83. or FC of heart muscle Lipolysis Glycogen Glycogen breakdown synthesis to glucose G protein + - Effector AC cAMP ATP Protein kinase Active Ca+2 release Phosphorylation Gs/Gi
  84. 84. Physical action • Absorption: Kaolin absorbs bacterilal toxin and thus acts as antidiarrhoeal agent. • Protectives:- Various dusting powders.
  85. 85. • Antagonist:- Which have only the affinity no intrinsic activity (IA=0). IA=0 so no pharmacological activity. • Rather these drug bind to the receptor and produce receptor blockade. • Atropine blocks the effects of Ach on the cholinergic muscarinic receptors.
  86. 86. Physical Action • Osmosis:- MgSo4 acts as a purgative by exerting osmatic effect within lumen of the intestine. • Astringents:- They precipitate the surface proteins and protect the mucosa Ex: tannic acid in gum patients • Demulcent:- These drugs coat the inflamed mucus membrane and provide soothing effect. Ex: Menthol
  87. 87. False incorporation • Bacteria synthesis folic acid from PABA (Para Amino Benzoic Acid), for growth sand development. • Sulfa drugs resemble PABA, therefore falsely enter into the synthesis process of PABA, cause nonfunctional production and no utility for bacterial growth.
  88. 88. Protoplasmic poison • Germicides and antiseptics like phenol and formaldehyde act as non specifically as protoplasmic poison causing the death of bacteria
  89. 89. Through formation of antibodies • Vaccines produce their effect by inducing the formation of antibodies and thus stimulate the defense mechanism of the body • Ex:- Vaccines against small pox and cholera
  90. 90. Targeting specific genetic changes. • Anti cancer drugs that specifically target genetic changes. • Inhibitors of specific tyrosine kinase that that block the activity of oncogenic kinases.
  91. 91. Physiological antagonism • Two antagonists, acting at different sites, counter balance each other by producing opp. effect on same physiological system. • Histamine –Vasodilatation • Nor epinephrine – Vasoconstriction
  92. 92. Chemical action 1.Ion Exchanges:-Anticoagulant effect of heparin(-ve charge) antagonized by protamine (+ve charged) protein. 2.Neutralization:- Excessive gastric acid is neutralized by antacids. 3. Chelation:-These are trap the heavy metals. Ex:-EDTA, BAL.

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