Introduction to Pharmacology

1. Introduction to Pharmacology By SindhuPriya E S

2. Introduction Pharmacology (Greek) • Pharmacon – Drug / Active principle • Logos - discourse in / study Pharmacology means “THE SCIENCE OF DRUGS”

3. Definition • It is the study of substances that interact with living systems through chemical process, especially by binding to regulatory molecules & activating or inhibiting normal body process • It deals with the interaction of exogenously administered chemical molecule (Drug) with living system

4. History Oswald Schmiedeberg Father of Pharmacology Rudolf Buchheim – 1847 First institute of pharmacology

5. Drug discovery and development process

6. Divisions of pharmacology • Pharmacodynamics • What the drug does to the body • It includes physiological and biochemical effects of drugs • Explains mechanism of action at molecular level • Pharmacokinetics • What the body does to the drug • It includes movement and alteration of the drug in the body • Absorption, Distribution, Metabolism and Excretion

7. Drug • Derived from french word “Drogue” which means “Dry herb” • Any substance that brings change in biological function through its chemical action • It alters state of the body- • Can’t create new function but alters existing function

8. WHO definition of DRUG • Drug is any substance or product that is used or is intended to be used to modify or explore physiological systems or pathological states for the benefit of the recipient

9. receptors • Specialized target macromolecules present on the cell surface or intracellularly

10. Other branches of pharmacology • Pharmacotherapeutics It is the application of pharmacological information together with knowledge of the disease for its prevention, mitigation or cure • Clinical pharmacology It is the scientific study of drugs in man • Chemotherapy It is the treatment of systemic infection/malignancy with specific drugs that have selective toxicity for the infecting organism malignant cell with no/minimal effects on the host cells.

11. Other branches of pharmacology • Pharmacy It is the art and science of compounding and dispensing drugs or preparing suitable dosage forms for administration of drugs to man or animals. • Toxicology It is the study of poisonous effect of drugs and other chemicals (household, environmental pollutant, industrial, agricultural, homicidal) with emphasis on detection, prevention and treatment of poisonings.

12. Application of pharmacology • To control speed of onset, intensity of drug effect and duration of action • To identify the possible side effect and withdrawl symptoms of the drugs • To avoid adverse effects, drug interactions and contraindications of drugs • To avoid treatment failure due to tolerance and resistance • To control misuse of drugs

13. Nature and source of drugs Drugs will be obtained from different sources • Natural • Semisynthetic • Synthetic • Biosynthetic

14. 1. Natural Drugs a. Plants: -Digoxin from Digitalis purpurea -Atropine from Atropabelladona -Quinine from Cinchona officinalis b. Animals: -Insulin from pork/beef -Cod liver oil from Cod fish liver c. Minerals: -Iron, Iodine, Potassium salts d. Microorganisms: -Penicillin from Penicilliumnatatum -Chloramphenicol from Streptomycesvenezulae (Actinomycetes)

15. 2. Semi synthetic drugs: These are prepared by chemical modification of natural drugs Eg: Ampicillin from Penicillin G 3. Synthetic drugs: These are synthesized drugs in pharmaceutical laboratory Eg: Sulphonamides, Quinolones, Barbiturates 4. Biosynthetic drugs: These are prepared by cloning of human DNA into the bacteria like E.coli Eg:Human Insulin (Humilin), human Gh

16. Drug nomenclature A drug has 3 categories of names • Chemical name (IUPAC ) / Scientific name: • Based on molecular structure of the drug • Very long, too complex to use in common practice Eg:1-(lsopropylamino)-3-(1-naphthyloxy) prop an-2 -ol for propranolol • Non-proprietary name / Generic name: • Given by approval authorities • Short hand version of chemical name • Recommended in Rx Eg: Meperidine (Pethidin), Lidocaine (lignocaine)

17. Drug nomenclature • Proprietary name / Brand name: • Given by pharmaceutical companies • It will be costly Eg: ALTOL, ATCARDIL, ATECOR, ATEN, BETACARD, LONOL, TENOLOL, TENORMIN for atenolol

18. Essential drugs WHO Definition: Essential drugs are the drugs which satisfy the priority healthcare needs of the population They are selected with due • regard to public health relevance • efficacy and safety • comparative costeffectiveness

19. Need for essential drug list They should be available within the context of functioning health systems • At all times • In adequate amounts • In appropriate dosage forms • With assured quality and adequate information • At an affordable price

20. WHO prepared its first Model List of Essential Drugs in 1977 • This has been revised from time to time and the current is the 15th list (2007) • India produced its National Essential Drugs List in 1996 • It has been revised in 2003 with the title "National List of Essential Medicines" • This includes 354 medicines

21. Orphan drugs • These are drugs or biological products for diagnosis/treatment/prevention of a rare disease or condition Eg: sodium nitrite, fomepizole, liposomal amphotericin, ancrod, rifabutin, succimer, somatropin, digoxin immune Fab (digoxin antibody), liothyronine (T3)

22. Routes of administration • Oral • Sublingual • Transdermal • Rectal and vaginal • Topical-skin, mucous membrane • Inhalation • Nasal • Parenteral – intradermal, subcutaneous, intravenous, intramuscular, intrathecal

23. Different routes of administration and first pass metabolism

24. Factors governing choice of route • Drug characteristics • Site of action • Effect of digestive juices and first pass metabolism • Onset of action • Rapidity of response (routine or emergency) • Accuracy of dose required (i.v. and inhalational) • Liver and kidney diseases • Patient condition (unconcious)

25. Oral route (p.o) It is oldest and commonest mode of drug administration Advantages • Convenient mode • Noninvasive • Painless • Economical • Can be self administered • Both solids and liquids can be taken Disadvantages • Slow absorption • Slow action • Irritable and unpalatable • Cannot be used for uncooperative/ unconciuos patients • May cause nausea / vomiting • First pass effect

26. Sublingual route / buccal • The tablet or pellet containing drug is placed under the tongue or crushed in the mouth and spread over the buccal mucosa • Lipid soluble and non-irritating drugs can be administered Advantages • Economical • Quick termination • First pass avoided • Drug absorption is quick • Can be self administered Disadvantages • Unpalatable & bitter drugs • Irritation of oral mucosa • Large quantities can’t be given • Few drugs are absorbed

27. Cutaneous routeTransdermal drug delivery system • The drug is delivered at the skin surface by diffusion for percutaneous absorption into circulation • Drug delivery at constant and predictable rate Backing film Drug reservoir Rate controlling micropore membrane Adhesive layer with priming dose Capillary 27 27

28. Rectal route Advantages • Used in children • Little or no first-pass effect • Used in vomiting / unconscious conditions • Higher concentrations are achieved rapidly Disadvantages • Inconvenient • Irritation or inflammation of rectal mucosa can occur • Absorption is slow and erratic Vaginalroute Drugs may be administered in the vagina in the form of pessaries Eg: Antifungal vaginal pessaries 28 28 28

29. inhalation • The drug is inhaled into lungs directly • Gaseous and Volatile drugs. Eg: Anesthetic agents Advantages • Rapid onset of action • Absorption takes place from vast surface of alveoli • First pass metabolism is avoided Disadvantages • Irritant vapours cause inflammation of respiratory tract nasal • The drug is administered into nasal cavity in the form of spray or nebulizer or drops • Mucous membrane of nose can readily absorb many drugs • Digestive juices and liver bipassed

30. topical • Skin • Dermal- Drugs applied as ointment, cream, lotion, paste, powder, spray, oil etc • Transdermal – absorption of drug through skin • Mucous membrane • The dosage form depends on the site of application • Eye drops, eardrops, nasal drops, antiseptics, sunscreen, jellys etc…

31. Parenteral route The drug is injected directly into the tissue fluid or blood without crossing intestinal mucosa

32. Intravenous (i.v.) • The drug is injected as bolus / infused slowly in one of the superficial veins • Drug directly reaches blood stream Advantages • 100% bioavailability • Precise, accurate and immediate onset of action • First pass avoided • Highly irritant drugs can be injected • Drugs which are not absorbed orally can be given Disadvantages • Cannot be self administered • High risk of adverse effects • High conc. Achieved rapidly • Risk of embolism • Thrombophlebitis and necrosis

33. Intramuscular (i.m.) • The drug is injected in one of the large skeletal muscle- deltoid, triceps, gluteus maximus, rectus femoris Advantages • Fastonset of action • First pass avoided • Mild irritants can be injected Disadvantages • Cannot be self administered

34. Intradermal • The drug is injected in to the skin raising a bleb • This route is employed for specific purpose only • Eg: BCG Vaccine, small pox vaccine Subcutaneous • The drug is deposited in the loose subcutaneous tissue rapidly supplied by nerves • Irritants cannot be injected • Tissue is less vascular. Hence absorption is slow