Basic Concepts of Pharmacology

1. Basic Concepts of Pharmacology Jan Bazner-Chandler CPNP, CNS, MSN, RN

2. Cellular Physiology • What does a cell do? • Exchange material • Obtain energy from nutrients • Synthesize hormones, neurotransmitters, enzymes, structural proteins and other complex molecules • Duplicate themselves

4. Pharmacokinetics • Drugs movement through the body to reach sites of action, metabolism and excretions.

5. Drug Transport • What does this have to do with drug administration? • Drugs must reach and interact with or cross the cell membrane to stimulate or inhibit cellular function.

6. Key Concepts • Absorption • Distribution • Metabolism • Excretion • Serum Drug Levels • Serum Half-life

8. 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.

9. 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

10. Oral 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.

11. Oral Drugs • Drug needs to be taken orally – pill v liquid – size of pill – make up of pill • Time in the stomach – is the stomach empty or full • Very few drugs actually absorbed in the stomach • Small intestine – large surface area for absorption of nutrients and minerals – most drugs absorbed in small intestine

12. Amoxicillin Suspension

13. Amoxicillin Chewable Tablets

14. Amoxicillin Capsule

15. 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

16. IM and Sub-Q • IM – intramuscular – into a muscle group – pain medications / antibiotics / vaccinations • Sub-Q – into subcutaneous tissue – (Coumadin / heparin / Lovenox) (TB test)

17. Subcutaneous Injection

18. Intramuscular or IM

19. Intravenous

20. Local Administration • Adhesive patches – pain control, nitroglycerine patches, hormones, birth control patches, nicotine patches • Topical application – sunscreen, antibiotic ointments, cortisone • Eye, ear, nose drops • Vaginal or rectal (PR)

21. Nitroglycerine Ointment

22. Nitroglycerine Patch

23. Eye Drops or Eye Ointment

24. Ear Drops

25. Rectal Suppositories

26. 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

27. Inhaled • Asthmatic drugs • Anesthetics

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

30. 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.

31. 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

32. Three ways to get in! • Direct penetration of the membrane • Protein channels • Carrier proteins

33. # 1 Lipid Soluble Drugs • Lipid soluble drugs are able to dissolve in the lipid layer of the cell membrane • No energy expended by the cell • Passive diffusion • Oral tablets or capsules must be water soluble to dissolve in fluids of the stomach and small intestine

34. # 2 Protein Channels • Most drug molecules are to big to pass in to the cell via the channels – small ions such as sodium and potassium use the protein channels but their movement is regulated by gating mechanisms – only small amounts allowed.

35. # 3 Carrier Proteins • Molecule needs to bind with a protein that will transport it from one side of the cell membrane to another – a drugs structure determines which carrier will transfer it.

36. 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.

37. 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

38. 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

39. Excretion • Refers to the elimination of the drug from the body. • Requires adequate functioning of the circulatory system and organs of excretion. • Kidneys • Bowels • Lungs • Skin

40. Serum Drug Levels • Laboratory measurement of the amount of drug in the blood at a particular time • A minimum effective concentration (MEC) must be present before a drug exerts its action on a cell.

41. Toxic Levels • Excessive level of a drug in the body • Single large dose • Repeated small doses • Slow metabolism which allows drug to accumulate in the body

42. Yes, laboratory values are important! • Serum drug levels indicate the onset, peak and duration of the drug action. • Testing: involves drawing multiple measurements of blood levels of a drug over time.

43. Do we do serum drug levels for all drugs? • No • When do we need them? • Drugs with narrow margin of safety (digoxin, aminoglycoside antibiotics, lithium). • To check to see if the drug is at therapeutic levels – seizure medications. • When a drug overdose is suspected.

44. Important concept! • Serum half-life or elimination half-life is the time it takes the serum concentration of the drug to reach 50% • A drug with a short half-life requires more frequent administration • A drug with a long half-life requires less frequent administration

45. Why is this important? • Half-life determines how often a drug is given • Daily in the morning • At bedtime • Q.I.D - four times a day • T.I.D – three times a day • Q4 hours – every four hours • Q 12 hours – 9 am and 9 pm

46. Pharmacodynamics Drug actions on target cells and resulting cellular biochemical reaction of in simple terms “What the drug does to the body”.

47. Receptor Theory • Most drugs exert their effects by chemically biding with receptors at the cellular level. • Receptors are proteins located • on the surfaces of cell membranes • within the cells

48. What do the receptors do? • The receptors are often described as the lock into which the drug molecule fits as a key. • All body cells do not respond to all drugs even when all the cells are exposed to the drug.

49. More is not better! • Number of receptors site available will effect drug action so giving a higher dose does not necessarily produce additional pharmacological effects.

50. Ibuprofen • Generic name: ibuprofen • Trade name: Advil, Motrin, Nu-ibuprofen, PediaCare • Therapeutic classification: Antipyretics, antiheumatics, analgesic, non-steroidal anti-inflammatory agent. • Pharmacologic classification: nonopioid analgesic.