Chapter 1  ·  Module 1

Introduction to Pharmacology

Section 1

The Pharmacokinetics / Pharmacodynamics Framework

Pharmacokinetics

What the Body Does to the Drug

Determines how much drug reaches the target, when, and for how long

  • Absorption — drug enters the bloodstream
  • Distribution — drug moves to tissues
  • Metabolism — drug is chemically altered
  • Elimination — drug leaves the body

Pharmacodynamics

What the Drug Does to the Body

Determines the nature and magnitude of the drug’s effect at the target

  • Drug binds molecular target (receptor, enzyme, channel, transporter)
  • Binding produces a biochemical effect
  • Effect magnitude relates to drug concentration at the target
  • Therapeutic index — ratio of toxic dose to effective dose

Section 2

Drug Names and Sources

Three-Name System

  • Chemical name — exact molecular structure; unwieldy, not used clinically
  • Generic name — standardized, publicly owned; encodes class via stems
  • Brand name — manufacturer-assigned; trademark-protected; multiple may exist for one generic

Four Drug Sources

  • Natural — morphine, digoxin, penicillin
  • Synthetic — most modern small-molecule drugs
  • Semisynthetic — ampicillin, oxycodone (natural core chemically modified)
  • Biologic — monoclonal antibodies, recombinant insulin, vaccines

Key Generic Name Stems — Class Recognition

StemDrug ClassExamples
-ololBeta-adrenergic blockersMetoprolol, propranolol, atenolol
-prilAngiotensin-converting enzyme inhibitorsLisinopril, enalapril, ramipril
-sartanAngiotensin II receptor blockersLosartan, valsartan, irbesartan
-statin3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitorsAtorvastatin, simvastatin
-prazoleProton pump inhibitorsOmeprazole, pantoprazole
-mabMonoclonal antibodiesRituximab, trastuzumab
-nibSmall-molecule kinase inhibitorsImatinib, erlotinib
-floxacinFluoroquinolone antibioticsCiprofloxacin, levofloxacin

Section 3

Drug Development Pipeline

Preclinical

Lab and Animal Studies

Is it safe enough to test in humans? Investigational New Drug application to Food and Drug Administration required before proceeding.

Phase I

20–100 Healthy Volunteers

Is it safe? What is the pharmacokinetic profile and maximum tolerated dose?

Phase II

100–500 Patients

Does it work? Preliminary efficacy. Most drugs fail here.

Phase III

Hundreds to Thousands of Patients

Does it work better than comparator? Pivotal randomized controlled trials. New Drug Application submitted on success.

Phase IV

Post-Approval Surveillance

What rare effects emerge in broader populations? Detects signals invisible in Phase III.

Approximately 90 percent of drugs that enter clinical testing do not receive approval — most commonly because of inadequate efficacy or unacceptable toxicity discovered in human trials.

Section 4

Routes of Administration

Enteral — via Gastrointestinal Tract

Oral

  • Most common; convenient; well-studied
  • Subject to first-pass metabolism in the liver
  • Bioavailability reduced by first-pass effect
  • Onset slower than parenteral routes

Enteral — Bypasses First-Pass Effect

Sublingual

  • Absorbed directly into venous drainage of mouth
  • Liver does not see drug before systemic circulation
  • Rapid onset
  • Prototype: nitroglycerin

Parenteral — 100% Bioavailability

Intravenous

  • Drug delivered directly into bloodstream
  • 100 percent bioavailability by definition
  • Fastest onset; most precise control
  • First choice in emergencies and critical care

Parenteral — Injection into Tissue

Intramuscular / Subcutaneous

  • Drug absorbed by diffusion into capillaries
  • Onset: intramuscular faster than subcutaneous
  • Subcutaneous enables depot formulations (e.g. insulin)
  • High bioavailability; avoids first-pass effect

Parenteral — Pulmonary Delivery

Inhalation

  • Large pulmonary surface enables rapid absorption
  • Maximizes drug at airway target
  • Minimizes systemic exposure
  • Preferred for bronchodilators and inhaled corticosteroids

Parenteral — Sustained Release

Transdermal

  • Drug absorbed through the skin
  • Slow, sustained release; avoids first-pass effect
  • Maintains relatively constant plasma concentrations
  • Examples: fentanyl patch, nicotine patch