Basic Principles of Pharmacology

UNIT TWO: BASIC PRINCIPLES OF PHARMACOLOGY

Pharmacokinetics

Pharmacokinetics focuses on the study of how drugs are absorbed, distributed, metabolized, and excreted in the body. The primary processes involved in pharmacokinetics include:

  • Absorption: Movement of the drug from the site of administration into the bloodstream.
  • Distribution: Distribution of the drug throughout the body fluids and tissues.
  • Metabolism: Biochemical modification of the drug, primarily occurring in the liver.
  • Excretion: Elimination of the drug and its metabolites from the body, typically through urine or feces.
Study Questions
Matching: Drug Change and Movement Terms

Match the following terms with their appropriate definitions:

  1. Absorption
    • e. Movement into the blood
  2. Distribution
    • c. Movement from blood into tissue and cells
  3. Metabolism
    • a. Change in drug structure
  4. Excretion
    • f. Movement out of the body
  5. Pharmacokinetics
    • d. Movement into and out of the body
  6. Elimination
    • b. Change in drug structure and movement out of the body
Matching: Methods of Drug Movement and Characteristics

Match the method of movement with their characteristics:

  1. May require energy or pores
    • c. Passage with the aid of a transport system
  2. Requires small size
    • a. Passage through channels
  3. Requires lipid solubility
    • b. Direct penetration of the membrane
True or False Statements
  1. Cell membranes are composed of fat with phosphate.
    • F
  2. Most drugs enter cells through channels or pores.
    • F
  3. P-glycoprotein transports many drugs out of cells.
    • T
  4. A transport mechanism is needed for a water-soluble drug to enter a cell.
    • T
  5. Ionization is a process that allows a drug to enter a cell.
    • F
  6. If a quaternary ammonium compound drug is injected into a vein, it will produce effects, but it will not if taken orally.
    • T
  7. Polar drugs can enter fetal circulation and breast milk.
    • F
  8. Aspirin, like most drugs, is primarily absorbed in the small intestine.
    • T
  9. Enteric drugs should not be crushed because crushing these preparations can cause stomach distress or alter the drug due to stomach acid.
    • T
  10. A depot intramuscular (IM) injection of an antibiotic to treat syphilis will be completely effective within 24 hours after administration.
    • F
  11. The protein-bound portion of a drug in circulation is not able to exert its action.
    • T
  12. First-pass effect means most of the drug is activated by the liver, so it must be administered orally.
    • F
  13. A drug with extensive first-pass effect may be given sublingually to allow absorption directly into the systemic circulation.
    • T
  14. Adding a drug to a patient's drug regimen can cause other drugs to be metabolized more slowly or more rapidly.
    • T
  15. Intestinal enzymes can release drugs from bile in the duodenum, causing the drug to be reabsorbed.
    • T
  16. The nurse would expect that an intravenous (IV) antibiotic prescribed for bacterial meningitis would most likely get to the site of infection if the drug is water-soluble.
    • T
  17. Chemotherapy is administered through a central intravenous line because chemotherapy is caustic to the vein, and a large central vein has rapid blood flow, which dilutes and moves the medication quickly.
    • T
Key Points
  • P-glycoprotein functions in drug transport, specifically in moving drugs out of cells, often impacting drug efficacy and resistance.
  • Polar drugs face challenges in crossing cell membranes; they often require specific transport mechanisms to facilitate entry.
  • First-pass metabolism can significantly affect the bioavailability of orally administered drugs, making alternative routes (like sublingual) necessary for some medications.
  • Depot IM injections are designed for sustained release, but the onset of therapeutic effects may take longer than 24 hours and is influenced by the drug's formulation and characteristics.
  • Enteric-coated medications provide protection against stomach acid, which is why it is emphasized they should not be crushed.
  • Understanding the principles of pharmacokinetics is crucial for effective medication administration and optimization of therapeutic outcomes.