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. Generic and Trade Name • Generic name: acetaminophen • Less expensive – chemically similar to trade name drugs • Trade name: Tylenol, Tempra, Datril • More expensive

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

9. Dosage Forms • A variety of dosage forms exist to provide both accurate and convenient drug delivery systems. • These delivery systems are designed to achieve a desired therapeutic response with minimal adverse effects.

10. Dosage Forms • Enteral: taken by mouth or PO • Parenteral: intramuscular or intravenous • Topical: applied to the skin, a patch, suppositories (rectal or vaginal)

11. Dosage Form • Parenteral • Injections • Solutions • Suspensions • Emulsions • Powders for reconstruction • Sublingual or buccal

12. Chewable Tablets

13. Chewable Tablets • Can be chewed • Used for children • Used in the client that has a hard time swallowing pills • Break down of the drug starts in the mouth

14. Tablet

15. Tablets • Are made to be swallowed whole • Are often scored so a half-dose can be give

16. Capsules

17. Capsules • To be swallowed whole • Often are sustained release – 12 or 24 dosing

18. Enteric Coated Tablets

19. Enteric coated • Tablets are coated so that they do not break down in the stomach • Absorption of the drug takes place in the small intestine. • Cannot be divided into smaller doses

20. Sublingual

21. Sublingual • The tablet is put under the tongue • Medication is absorbed through the buccal mucosa. • Used in drug like nitroglycerine used to reduce chest pain.

22. IM and SC

23. Intramuscular or subcutaneous • IM or the “shot” – injected into the deep muscle of buttocks, thigh or upper arm • Antibiotics • Pain medications • Subcutaneous – injected into the fat layer just below the skin • Insulin • Anticoagulation meds: Heparin of Lovenox

24. Intravenous or IV

25. Intravenous or IV • Medication is administered right into the vein. • Medications is readily absorbed right into the circulation. • Antibiotics • Regular insulin only • Pain medications • Anti-nausea or anti-emetics • Chemotherapy

26. Local Administration • Adhesive patches • pain control • nitroglycerine patches • Hormones • birth control patches • nicotine patches

27. Topical Applications • Sunscreen • Antibiotic ointments • Cortisone

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

29. Eye Drops or Eye Ointment

30. Ear Drops

31. Vaginal or Rectal (PR)

32. 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

33. acetaminophen (Tylenol) Suppository

34. Pharmacodynamics • The mechanism by which specific drugs produce biochemical and physiologic changes in the body.

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

36. 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.

37. 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

38. 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.

39. 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.

40. 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.

41. 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

42. 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

43. 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

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

45. 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.

46. 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.

47. 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

48. 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.

49. 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

50. 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