Pharmacology - Basic Principles

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Overview

Pharmacology is the study of drugs. Though many are not typically prescribed by physiotherapists/physical therapists, knowledge of this field is pertinent to the care of patients and clients. Knowledge of drugs, drug metabolism, and their effects on the various systems of the body enhances a clinician's ability to educate patients, monitor patient outcomes, and engage in interprofessional discussions with pharmacists, physicians, etc.

Drug Nomenclature

A drug is a substance taken that can alter or modify one or more functions when introduced to the body. These substances are referred to by multiple names, as follows:

• Chemical Name (scientific name)
• Generic Name (nonproprietary name)
• Trade Name/Brand Name (proprietary name)

Drug Efficacy

• dose-response curve
• ED50, TD50, TI
• Toxicology definition

Common Routes of Drug Administration

• Enteral routes of administration utilize the GI tract. They are as follows:
  • Oral - most commonly used route of administration
    • Drug absorption primarily occurs in the small intestine
      • Greatly affected by the first-pass effect (large portion of drug is metabolised in the liver, reducing the concentration of the drug)
  • Sublingual (under the tongue) and buccal (through the cheek)
    • sublingual tissue is more permeable than buccal, allowing for faster drug absorption
    • Circumvents first-pass effect
  • Rectal
    • partially bypasses first-pass effect (50% absorption in the liver)
• Parenteral
  • Intravenous (IV): injection into peripheral veins, typically in the upper extremity
    • Upper extremity IVs have decreased incidence of Thrombophlebitis and Thrombosis compared to the lower extremity
  • Intramuscular
  • Subcutaneous: administered to the cutis (below dermis and epidermis)
    • slow, sustained absorption due to minimal vasculature
  • Intra-arterial: not commonly used for medications, used for contrast injections for angiography studies and chemotherapy
• Other
  • Transnasal: utilizes drug absorption via passive diffusion into systemic circulation
  • Inhalation: rapid delivery to respiratory tract epithelium
  • Topical: remains on surface of local application
  • Transdermal: penetrate into skin layers, local application of a drug