PHARMA(P1&2)-LESSON-BSN-2D

• Pharmacology is the study of the action of chemicals on biologic systems
• Medical pharmacology is concerned with the use of chemicals in the prevention, diagnosis, and treatment of disease
• Toxicology is the study of the undesirable effects of chemicals on biologic systems
• Pharmacotherapeutics is the use of medications to prevent, treat, cure, or alleviate symptoms of disease
• Pharmacokinetics explains the effects of the body on drugs, including absorption, distribution, metabolism, and elimination
• Pharmacodynamics is the actions of the drug on the body
• Drugs are substances that act on biologic systems at the chemical level and alter their functions
• Drug receptors are the molecular components of the body with which drugs interact to bring about their effects
• Drug names:

  • Chemical name: N - (4 - Hydroxyphenyl)acetamide
  • Generic name: acetaminophen/paracetamol
  • Trade name: Biogesic
• Physical nature of drugs:

  • Solid (e.g. Aspirin tablet)
  • Liquid (e.g. Nicotine, Ethanol)
  • Gas (e.g. Nitrous oxide)
• Drug-receptor bonds:

  • Covalent: very strong & irreversible reaction
  • Electrostatic: between cation and anion; weaker than covalent bond
  • Hydrophobic: quite weak; important in interactions of highly lipid-soluble drugs
• Drug shape permits binding to its receptor site, must fit perfectly to yield a response
• Chirality: ability of a drug to exist as optically active stereoisomers or enantiomers
• Rational drug design is the ability to predict the appropriate molecular structure of a drug based on information about its biologic receptor
• Pharmacokinetics includes absorption, distribution, metabolism, and elimination of drugs
• Movement of drugs in the body starts from the site of administration towards the site of action
• Permeation is the movement of drug molecules into and within the biologic environment
• Ways drugs act on the body:

  • Turn on bodily functions
  • Turn off bodily functions
  • Neutralize bodily functions
• Transport by special carriers for drugs that do not readily diffuse through membranes
• Endocytosis is the binding of the transported molecule to specialized components on cell membranes
• Volume of distribution (Vd) is the ratio of the amount of drug in the body to the drug concentration in the plasma or blood
• Clearance is the ratio of the rate of elimination of a drug to the concentration of the drug in the plasma or blood
• Bioavailability is the fraction of the administered dose of drug that reaches the systemic circulation
• Area under the curve (AUC) is the graphic area under a plot of drug concentration versus time after a single dose
• Minimum effective concentration (MEC) is the plasma drug concentration below which a patient's response is too small for clinical benefit
• Absorption of drugs is the movement of the drug into the bloodstream after administration
• Oral route of administration is the most common and is subject to the first-pass effect before reaching the systemic circulation
• Pharmaceutical preparations for oral administration:

  • Tablets
  • Enteric-coated preparations
  • Sustained-release preparations
• Sustained-release preparations:

  • Capsules filled with tiny spheres that contain the actual drug
  • The drug is released steadily throughout the day
  • Primary advantage: permits a reduction in the number of daily doses
  • In a regular tablet, you need to take 3 tablets in a day, but with sustained-release preparations, it can be lessened into 1 capsule a day
  • Disadvantages: high cost; potential for variable absorption
  • Spheres are slower to dissolve than others
• Buccal and sublingual administration:

  • Direct absorption into the systemic venous circulation, bypassing the hepatic circuit
• Intravenous administration:

  • Instantaneous and complete absorption (bioavailability is 100%)
  • IV administration is more dangerous
  • Administered in a 25-degree angle
• Intramuscular administration:

  • Often faster and more complete than with oral administration
  • Large volumes may be given through IM, if the drug is not too irritating
  • E.g. vaccines
• Subcutaneous administration:

  • Slower absorption than the intramuscular route
• Rectal (suppository) administration:

  • The rectal route offers partial avoidance of the first-pass effect
  • Used for larger amounts of drugs or drugs that have an unpleasant taste
• Inhalation administration:

  • Route offers delivery closest to respiratory tissues
  • Usually very rapid absorption
• Topical administration:

  • Includes application to the skin or to mucous membranes for local effect
• Transdermal administration:

  • Involves application to the skin for systemic effect
• Factors affecting drug absorption:

  • Rate of dissolution helps determine the rate of absorption
  • Surface area is a major determinant of the rate of absorption
  • Blood flow influences the rate of absorption
  • Lipid solubility affects the rate of absorption
  • pH partitioning affects passive diffusion across membranes
• Distribution of drugs:

  • Movement of the drug from the circulation to body tissues
• Determinants of distribution:

  • Size of the organ determines the concentration gradient between blood and the organ
  • Blood flow influences tissue concentrations
  • Solubility influences drug concentration in extracellular fluid
  • Binding of a drug to macromolecules increases drug concentration in that compartment