Pharmacologic Principles

1. Pharmacologic Principles Jan Bazner-Chandler RN, MSN, CNS, CPNP Chapter 2

2. Pharmacology • The study or science of drugs • Knowledge of pharmacology allows nurse to understand how drugs affects humans.

3. Naming the drugs • Chemical name • Generic name • Trade name

4. Chemical name • Chemical composition and molecular structure

5. Generic Name • Shorter and simpler than the chemical name

6. Trade Name • Drugs registered trade mark

7. Pharmaceutics • How dosage forms influence the way in which the body metabolizes a drug and the way the drug affects the body.

8. Dosage Forms • Tablets • Capsules • Sustained release tablet • Injection – “shot” • Sublingual – under the tongue • Intravenous - IV or directly into the vein • Topical

9. Chewable Tablets

10. Tablet

11. Capsules

12. Enteric Coated Tablets

13. Sublingual

14. IM and SC

15. Intravenous or IV

16. Pharmacodynamics • The mechanism by which specific drugs produce biochemical and physiologic changes in the body. • A given drug interacts with specific receptor sites: agonist drugs stimulate receptors, antagonist drugs inhibit receptors • Causes general interaction with cell metabolism • Cellular environment and function are altered to produce the desired response.

17. Pharmacokinetics • Movement of drugs across body membranes to reach the target organ. • 4 ways drugs move throughout the body: • Absorption • Distribution • Metabolism • Excretion

18. Absorption • Process that occurs from the time the drug enters the body to the time it enters the bloodstream to be circulated. • Onset of drug action is largely determined by the rate of absorption.

19. Absorption • Think of how the drug gets into the circulatory system and the dosage needed to bring the blood levels up to therapeutic levels. • Dosage • Interval of administration • Route of administration

20. Oral Drugs or PO Drugs • Dosage is determined by how much of the drug is required to be taken by mouth to given the desired affect. • Bioavailability – portion of the drug that reaches the systemic circulation.

21. First-pass • If a drug is metabolized by the liver before it reaches the systemic circulation, some of the active drug will be inactivated or diverted before it can reach the general circulation. • Most drugs administered by mouth have less than 100% bioavailability. • Drugs administered by the intravenous route have 100% bioavailability.

22. Critical thinking question • What are the effects on bioavailability in: • The infant that has an immature liver. • The geriatric patient with a poor functioning liver • The client with liver disease.

23. Where does absorption happen? • Very few drugs actually absorbed in the stomach (alcohol) • Small intestine • large surface area for absorption of nutrients and minerals • most drugs absorbed in small intestine

24. Degree and Rate of Absorption • Depends on • Route • Age and physical condition of client • Lipid or water solubility of drug • Potential drug interactions with other drugs

25. What else might influence oral drug absorption? • Food in stomach • Certain juices – grapefruit juice • Milk – binds with molecules of some drugs so that the drug is never absorbed • Orange juice – enhances absorption of iron taken orally • The coating on the tablet: chewable, enteric coated, slow release capsules

26. Local Administration • Adhesive patches – pain control, nitroglycerine patches, hormones, birth control patches, nicotine patches

27. Eye, Ear and Nose Drops Drops written as gtts

28. Eye Drops or Eye Ointment

29. Ear Drops

30. Vaginal or Rectal (PR)

31. Rectal Suppositories • Excellent route of administration of medications for the client that is: • Vomiting / nausea • Refuses to take medication PO • Difficulty swallowing a medication • Infants – fever or pain medications

32. acetaminophen (Tylenol) Suppository

33. Topical Applications • Sunscreen • Antibiotic ointments • Cortisone

34. Distribution • Transportation of drug molecules within the body after the drug is absorbed into the blood stream.

35. Distribution • Drug needs to be carried to the site of the action. • Carried by the blood and tissue fluids to the sites of pharmacological action. • Distribution depends on adequacy of blood circulation.

36. Key Concepts of Distribution • Protein binding – drug molecules need to get from the blood plasma into the cell. • Protein binding allows part of the drug to be stored and released as needed. • Some of the drug is stored in muscle, fat and other body tissues and is gradually released into the plasma.

37. Just how does the drug get into the cell? • Drug must pass though the capillary wall • Blood brain barrier – very effective in keeping drugs from getting into the central nervous system or CNS – limits movement of drug molecules into brain tissue

38. Metabolism • Method by which the drugs are inactivated or biotransformed by the body. • Most drugs metabolized in the liver by cytochrome P450 (CYP) enzyme. • Hepatic drug metabolism or is major mechanism for terminating drug action and eliminating drugs from the body.

39. What can stop this process? • Enzyme inhibition • Other drugs • Combination drugs • Liver disease • Impaired blood circulation in person with heart disease • Infant with immature livers • Malnourished people or those on low-protein diets

40. An important concept! • First-pass effect – some drugs are extensively metabolized or broken down in the liver and only a part of the drug is released into the systemic circulation • This is why dosage is important – how much drug needs to be taken in to give the desired effect and how often does it need to be taken

41. Excretion • Refers to the elimination of the drug from the body. • Requires adequate functioning of the circulatory system and organs of excretion. • Kidneys via urine • Liver via bile and into the feces • Lungs via exhaled air • Saliva, tears and sweat or skin

42. Important concepts • Absorption – small intestine, skin, rectal or vaginal tissue • Metabolism – liver • Distribution – circulation (blood or plasm) • Excretion – urine, stool, skin

43. Dosing Schedules • Determined by drug’s pharmacokinetic properties • Route of administration • Onset of action • Peak concentration level • Duration of action • Half-life

44. Onset, Peak, Elimination

45. Onset of action • The time when the drug’s effects first become noticeable.

46. Peak Concentration • Maximum blood concentration level achieved through absorption; at this level most of the drug reaches the site of action and provides therapeutic response.

47. Duration • Duration of action: the length of time a drug acts on the body.

48. Half-life • The time required for a drug’s plasma concentration to decrease to 50%.

49. Pharmacodynamics • Study of what the drug does to the body.

50. Pharmacotherapeutics • Therapeutic effect: the clinical indication for administering the drug. • Prevent disease • Treat disease