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Basic Concepts of Pharmacology

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

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Basic Concepts of Pharmacology

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  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

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

  4. 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

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

  6. 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

  7. 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 – full – does it make a difference on how drug is absorbed • Small intestine – large surface area for absorption of nutrients and minerals

  8. Amoxicillin Suspension

  9. Amoxicillin Chewable Tablets

  10. Amoxicillin Tablets

  11. 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 (breakdown occurs in small intestine), slow release capsules

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

  13. Subcutaneous Injection

  14. Intramuscular or IM

  15. 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)

  16. Nitroglycerine Ointment

  17. Nitroglycerine Patch

  18. Eye Drops or Eye Ointment

  19. Ear Drops

  20. Rectal Suppositories

  21. 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

  22. Inhaled • Asthmatic drugs • Anesthetics

  23. Distribution • Transportation of drug molecules within the body • Drug needs to be carried to the site of the action • Need blood to circulate the drug • Heart, liver, kidneys

  24. 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

  25. 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

  26. Blood Brain Barrier • This is especially important when treating infections of the brain such as meningitis, encephalitis, or brain abscess • Medications must be able to penetrate the blood brain barrier • Medications usually given intravenous

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

  28. # 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

  29. # 2 Protein Channels • Most drug molecules are to big to pass in to the cell via these channels – • But small ions such as sodium and potassium use the protein channels but their movement is regulated by gating mechanisms – only small amounts allowed

  30. # 3 Carrier Proteins • Molecule needs to bind with a protein that force a shape change the protein shape to allow entry, transport it from one side of the cell membrane to another – a drugs structure determines which carrier will transfer it.

  31. Metabolism • Method by which the drugs are inactivated or biotransformed by the body • Active drugs contain metabolites that are excreted – skin, urine, stool • Most drugs metabolized in the liver mitochondria by cytochrome P450 (CYP) Cytochrome P450 enzymes also function to metabolize potentially toxic compounds, including drugs and products of endogenous metabolism such as bilirubin, principally in the liver.

  32. 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

  33. 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

  34. 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

  35. Laboratory Values • Laboratory values reflecting function of liver and kidneys need to be looked at. • BUN and Creatinine – kidney function • LFT or liver function tests: • ALT – alamine aminotransferase (elevated in hepatitis) • AST or SGOT– aspartate aminotransferase – elevated in liver disease • ALP – elevated in biliary tract disease • Bilirubin levels – infants – gallstones in adults

  36. 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.

  37. 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 • Slow excretion from the body by the kidneys or gastrointestinal tract

  38. Yes, laboratory values are important! • Serum drug levels indicate the onset, peak and duration of the drug action

  39. 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 drug overdose is suspected

  40. 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

  41. 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

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

  43. 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

  44. 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.

  45. 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.

  46. Variables that effect drug action • Dosage of the drug refers to frequency, size, and number of doses • Ibuprofen (generic) or Advil (trade name) • Dosage = 250 mg per tablet • Tablets are enteric coated • Children over 12 years or adults take 1 to 2 tablet every 4 to 6 hours • Not to exceed 6 tablets in 24 hours unless prescribed by a doctor

  47. Drug Dosing • Often the first dose is higher in an effort to bring the therapeutic blood serum levels up quicker

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