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Chapter 2

Chapter 2. Pharmacokinetics and Pharmacodynamics. Pharmacotherapeutics. The study of how drugs are used to treat, prevent, and diagnose disease and illness Pharmacokinetics – how the body assimilates, incorporates, and eliminates a drug Pharmacodynamics – how a drug affects the body.

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Chapter 2

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  1. Chapter 2 Pharmacokinetics and Pharmacodynamics

  2. Pharmacotherapeutics • The study of how drugs are used to treat, prevent, and diagnose disease and illness • Pharmacokinetics – how the body assimilates, incorporates, and eliminates a drug • Pharmacodynamics – how a drug affects the body

  3. You will be able to explain to an athlete… • Why it is important to take medications as prescribed by a physician • How drugs work • Why drugs work • How long a drug remains active • What the potential drug adverse effects are • Other general questions they ask

  4. What is a Drug? • A chemical that interacts with and affects living organisms to produce a biological response • A drug alters physiological functions by replacing, interrupting, or potentiating existing cellular functions • Primary or secondary effects

  5. Pharmacodynamics • Receptor Sites – a component of a cell to which a drug binds to produce an effect • Most drugs act at specific locations in tissues or organs • “lock and key” analogy (pgs 18-19) • Affinity – the force that makes 2 agents bind or unite • Efficacy – the capacity to elicit a response

  6. Dose Response • Threshold – lowest dose capable of producing a perceivable response • Potency – amount of a drug necessary to produce a desired effect • Figure 2-2 Pg 19

  7. Time Response • Determining the time response of a dose: • Latency – “onset of action”, time required to produce an observable effect • Maximal Effect – time required to reach peak efficacy • Duration of Action – time period over which a drug produces a response after a single dose

  8. Time Response • Influenced by: • Route of administration • Solubility of the drug • How fast the drug is distributed to action site • Time it takes to be inactivated and excreted from the body

  9. Therapeutic Index – the range in which desired effects are produced • Used to determine the safety parameters of doses

  10. Half-Life – determined by the time required to reduce by one-half the amount of the drug present in the body • Drugs have different & distinct half-lives • Comparison for drug elimination rates • Determines frequency with which multiple doses of a drug can be safely administered • Half-life does not change with the drug dose

  11. Pharmacokinetics • Absorption – speed, rate, and extent of absorption is dependant on its’ physical and chemical properties • Solubility of the drug • Surface area of intended site of action • Specific route of administration

  12. Enteral • Oral ingestion - safest, most common, convenient, economical route of administration • Taken by mouth = onset of action within 1 hour • Oral mucosa – sublingual or buccal routes • Vast capillary blood supply = dissolve rapidly

  13. Enteral • Preliminary passage or “first-pass metabolism” Figure 2-7 pg 24 • Solutions • Liquid form, syrups, elixirs • Capsules and tablets • Sustained-release

  14. Parenteral • Non-oral route of administration • Drug delivered directly to target site • Not subjected to first-pass metabolism • Routes include • Subcutaneous • Intramuscular • Intravenous • Intrathecal • Intra-articular

  15. Inhalation • Form of gases or fine mists • Lungs: large surface area and rich blood supply = effective means of absorbing and transporting meds into blood supply rapidly • Special devices propel meds onto alveolar and bronchial tissues

  16. Topical • Applied to skin or mucous membranes • Difficult to reach systemic circulation • Used to treat skin problems • Routes • Ointments • Creams • Transdermal patches

  17. Pharmacokinetics • Distribution – to act on a specific receptor site, the drug must pass through the different biological layers and then be transported to the site via the bloodstream • Cell membrane review

  18. Modes of transportation across cell membrane • Filtration • Diffusion • Active transport

  19. Pharmacokinetics • Metabolism – process of ridding the body of foreign substance (biotransformation) • Breakdown of original drug compound into metabolites, which are eliminated • Rate of metabolism • Liver is primary organ, specialized enzymes that metabolize drugs or foreign compounds

  20. Pharmacokinetics • Excretion • Routes of drug elimination • Urine, bile, feces • Lungs, salivary, sweat, mammary glands • Kidney is major organ • Patient Health

  21. Factors Affecting Drug Response • Age • Infants & older adults • Weight & Gender • Men vs. women • Dosing based on weight • Time of administration • With food vs. before meals

  22. Barriers to Drug Distribution • Blood-brain barrier • Placental barrier • Barriers inhibit certain chemicals in the bloodstream that may be dangerous or toxic to the individual or fetus

  23. Drug Safety • Five Rights of Drug Administration • Right drug • Right patient • Right dose • Right route • Right time

  24. Other guidelines: • Drug prescribed = Drug dispensed • Read Directions carefully • Missed dosing • Proper storage • Safe storage • Know medical history • Potentiation

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