pharmacology lec1 and 2

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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.

11. Distribution or Disposition

12. Metabolism

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).

18. Cell membrane

23. Occurs along concentration gradient. Non selective

24. Not saturable

25. Requires no energy

26. No carrier is needed

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.

30. Size of molecule involved Large molecules slowdiffusion

31. Distance the molecule has to travelShort distance increase diffusion

32. TemperatureHigh temperatures increasediffusion

33. Solubility of the molecule

35. Occurs against concentration gradient.

36. Requires carrier and energy.

37. Specific

38. Saturable.

39. Iron absorption.

42. Requires carriers

43. Selective.

44. Saturable.

45. No energy is required.

46. Selection is by size; shape; charge.

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

55. Oral administration

57. Gut wall

60. Dosage forms Capsules Tablets Syrup Suspension Hard- gelatin capsule Soft- gelatin capsule Tablets Spansule

61. Sublingual

62. Rectal administration

63. Parenteral administration Intradermal (I.D.) (into skin) Subcutaneous (S.C.) Intramuscular (I.M.) Intravenous (I.V.) (into veins) Intra-arterial (I.A.) (into arteries) Intrathecal (I.T.) (cerebrospinal fluids ) Intraperitoneal (I.P.) (peritoneal cavity) Intra - articular (Synovial fluids) Intracardial

65. Parenteral administration

66. Ampoule Vial

68. Suitable for drugs not absorbed by the gut.

70. Prolonged infusion of irritant drugs lead to venous thrombosis.

72. Could be used for irritant drugs.

74. Not accepted as self administration.

76. Slow to obtain sustained drug effect eg. Insulin but generally complete

78. Tissue damage from irritant drugs

79. Maximum of 2 ml injection

81. Mucous membrane of respiratory tract (Inhalation) e.g. asthma

82. Eye drops e.g. conjunctivitis

83. Ear drops e.g. otitis externa

84. Intranasal, e.g. decongestant nasal sprayTopical application

85. Inhalation

86. Nebulizer Atomizer

88. Avoid inactivation by first hepatic bypass eg. Nitroglycerine

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)

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.

96. A syrup has fast rate of absorption as compare to tablet

97. A capsule has fast rate of absorption than tablet