PHARMACOLOGY STUDY MODULE
Introduction to Pharmacology and Basic Drug Concepts
Learning Objectives
• Define pharmacology and explain its major branches.
• Differentiate pharmacokinetics from pharmacodynamics.
• Describe the major routes of drug administration.
• Explain absorption, distribution, metabolism, and excretion.
• Identify common factors that influence drug response.
• Recognize basic principles of safe medication administration.
1. What Is Pharmacology?
Pharmacology is the study of drugs and how they interact with living organisms. It includes how drugs
produce their effects, how the body handles drugs, and how drugs are used to prevent, diagnose, or treat
disease.
Pharmacokinetics – what the body does to the drug. It describes four major processes:
• Absorption – movement of a drug from its site of administration into the bloodstream.
• Distribution – movement of the drug from the bloodstream to tissues and organs.
• Metabolism – chemical modification of the drug, primarily in the liver.
• Excretion – removal of the drug and/or its metabolites from the body, commonly through the kidneys.
ADME = Absorption → Distribution → Metabolism → Excretion
Pharmacodynamics – what the drug does to the body. It focuses on drug effects, mechanisms of
action, receptor interactions, therapeutic effects, and adverse effects.
2. Routes of Drug Administration
Drugs can be administered through different routes depending on the medication, patient, and desired
speed of action.
Oral Route
The drug is swallowed and absorbed through the gastrointestinal tract.
• Advantages: convenient, usually inexpensive, and generally easy for patients to administer.
• Limitations: absorption can be affected by food and gastrointestinal conditions; some drugs undergo
significant first-pass metabolism in the liver.
Sublingual Route
The medication is placed under the tongue and absorbed through the oral mucosa. This can provide
relatively rapid absorption while avoiding much of the gastrointestinal tract and first-pass metabolism.
Intravenous (IV) Route
, The drug is administered directly into a vein.
• Advantages: rapid onset and predictable delivery into systemic circulation.
• Limitations: requires appropriate technique; medication errors can have rapid consequences; careful
monitoring may be required.
Intramuscular (IM) Route
Medication is injected into muscle tissue. The rate of absorption can vary depending on the drug
formulation and blood flow to the injection site.
Subcutaneous (SC) Route
Medication is injected into the tissue beneath the skin. It is commonly used for medications that require
relatively slow and sustained absorption.
Topical Route
Medication is applied directly to the skin or another external surface, often to produce a local effect.
3. Drug Absorption
Absorption is the movement of a drug from its administration site into systemic circulation.
Several factors can affect absorption, including:
• Route of administration
• Blood flow to the absorption site
• Drug formulation
• Food in the gastrointestinal tract
• Gastric and intestinal conditions
• Drug solubility
The route of administration can have a major effect on how quickly a drug reaches the bloodstream. IV
administration places the drug directly into systemic circulation, whereas an oral medication generally
must first pass through the gastrointestinal tract.
4. Drug Distribution
After entering the bloodstream, a drug is distributed throughout the body.
Distribution can be influenced by:
• Blood flow
• Tissue permeability
• Drug properties
• Plasma protein binding
• Body composition
Some drugs bind to plasma proteins, particularly albumin. Generally, the unbound portion of a drug is
more readily available to move into tissues and exert pharmacologic effects.
Introduction to Pharmacology and Basic Drug Concepts
Learning Objectives
• Define pharmacology and explain its major branches.
• Differentiate pharmacokinetics from pharmacodynamics.
• Describe the major routes of drug administration.
• Explain absorption, distribution, metabolism, and excretion.
• Identify common factors that influence drug response.
• Recognize basic principles of safe medication administration.
1. What Is Pharmacology?
Pharmacology is the study of drugs and how they interact with living organisms. It includes how drugs
produce their effects, how the body handles drugs, and how drugs are used to prevent, diagnose, or treat
disease.
Pharmacokinetics – what the body does to the drug. It describes four major processes:
• Absorption – movement of a drug from its site of administration into the bloodstream.
• Distribution – movement of the drug from the bloodstream to tissues and organs.
• Metabolism – chemical modification of the drug, primarily in the liver.
• Excretion – removal of the drug and/or its metabolites from the body, commonly through the kidneys.
ADME = Absorption → Distribution → Metabolism → Excretion
Pharmacodynamics – what the drug does to the body. It focuses on drug effects, mechanisms of
action, receptor interactions, therapeutic effects, and adverse effects.
2. Routes of Drug Administration
Drugs can be administered through different routes depending on the medication, patient, and desired
speed of action.
Oral Route
The drug is swallowed and absorbed through the gastrointestinal tract.
• Advantages: convenient, usually inexpensive, and generally easy for patients to administer.
• Limitations: absorption can be affected by food and gastrointestinal conditions; some drugs undergo
significant first-pass metabolism in the liver.
Sublingual Route
The medication is placed under the tongue and absorbed through the oral mucosa. This can provide
relatively rapid absorption while avoiding much of the gastrointestinal tract and first-pass metabolism.
Intravenous (IV) Route
, The drug is administered directly into a vein.
• Advantages: rapid onset and predictable delivery into systemic circulation.
• Limitations: requires appropriate technique; medication errors can have rapid consequences; careful
monitoring may be required.
Intramuscular (IM) Route
Medication is injected into muscle tissue. The rate of absorption can vary depending on the drug
formulation and blood flow to the injection site.
Subcutaneous (SC) Route
Medication is injected into the tissue beneath the skin. It is commonly used for medications that require
relatively slow and sustained absorption.
Topical Route
Medication is applied directly to the skin or another external surface, often to produce a local effect.
3. Drug Absorption
Absorption is the movement of a drug from its administration site into systemic circulation.
Several factors can affect absorption, including:
• Route of administration
• Blood flow to the absorption site
• Drug formulation
• Food in the gastrointestinal tract
• Gastric and intestinal conditions
• Drug solubility
The route of administration can have a major effect on how quickly a drug reaches the bloodstream. IV
administration places the drug directly into systemic circulation, whereas an oral medication generally
must first pass through the gastrointestinal tract.
4. Drug Distribution
After entering the bloodstream, a drug is distributed throughout the body.
Distribution can be influenced by:
• Blood flow
• Tissue permeability
• Drug properties
• Plasma protein binding
• Body composition
Some drugs bind to plasma proteins, particularly albumin. Generally, the unbound portion of a drug is
more readily available to move into tissues and exert pharmacologic effects.
