Pharmacokinetics Overview

Pharmacokinetics Overview

• Kinetics refers to the movement and action of drugs through the body.
• Involves four main processes: absorption, distribution, metabolism, and excretion (ADME).

Absorption

• Absorption is how a drug enters the bloodstream after administration.
• All administration routes, excluding intravenous, require absorption.
• Onset of action is the time for a drug to reach its minimum effective concentration.
• Peak effect occurs when the drug is at maximum effect and concentration.
• Duration of action is how long the drug remains effective above the minimum concentration.

Factors Affecting Absorption

• Route of Administration: Determines the speed of absorption (oral, sublingual, inhalation, subcutaneous, IM).
• Gastrointestinal Condition: Conditions such as surgical removal of the small intestine can impair absorption.
• Liver Function: Drugs absorbed in the small intestine are partially metabolized by the liver before entering circulation (first pass effect).
• Blood Supply: Increased blood flow enhances absorption; decreased blood flow reduces it.
• Pain and Stress: Can diminish absorption due to the body's autonomic response.
• Drug Formulation: Different forms (tablets, liquids, slow-release) affect absorption rates.

Distribution

• Distribution is the delivery of drugs from systemic circulation to tissues and target cells.
• Influenced by blood flow; drugs reach well-perfused organs more quickly.
• Solubility affects distribution; lipid-soluble drugs can cross cell membranes and the blood-brain barrier, while water-soluble drugs cannot.

Metabolism

• Also known as biotransformation, this process converts drugs into simpler compounds or deactivates them.
• Primarily occurs in the liver, which can be affected by liver disease and age.
• Lifestyle factors, such as smoking and alcohol use, can also impact metabolic rates.

Excretion

• Excretion refers to removing the drug and its metabolites from the body.
• Key excretion routes are the kidneys and liver; other routes include lungs (respiration), sweat, and breast milk.
• Proper kidney function is critical for drug elimination; impaired function can lead to accumulation and toxicity.

Pharmacology Fundamentals

• Pharmacology studies drugs’ effects and their interactions with living organisms.
• Branches include pharmacy (drug production), toxicology (harmful effects), and clinical pharmacology (therapeutic use).
• Nurses focus on pharmacotherapeutics, which addresses drug applications for treatment and prevention of disease.

Drug Nomenclature

• Chemical Name: Describes the drug's atomic/molecular structure.
• Generic Name: A nonproprietary name, used globally (e.g., Aspirin).
• Trade Name: The brand name given by the manufacturer (protected by copyright).

Legal Terms and Drug Classification

• Over-the-Counter (OTC) Drugs: Accessible without a prescription (e.g., acetaminophen).
• Prescription Drugs: Require a prescription due to potential side effects (e.g., antibiotics).
• Controlled Drugs: Subject to prescription regulations due to addiction risk (e.g., Valium).

Drug Sources

• Plants: Natural substances (e.g., morphine).
• Animals: Derived from animal compounds (e.g., insulin).
• Minerals: Naturally occurring elements (e.g., iron).
• Synthetic: Created in labs (e.g., ranitidine).
• Genetically Engineered: Biotechnologically developed (e.g., Hepatitis B vaccine).

Drug Actions and Side Effects

• Indications: Conditions treated by the drug (e.g., Benadryl for allergies).
• Actions: How the drug affects cellular functions.
• Contraindications: Conditions that preclude drug use.
• Side Effects: Unwanted effects that are not dangerous.
• Adverse Effects: Serious, harmful reactions (e.g., seizures).
• Interactions: Drugs/foods that can alter a drug's effect negatively.

Summary of Implications for Student Nurses

• Students should understand pharmacodynamics, pharmacokinetics, and patient safety in drug administration.
• Emphasis on medication monitoring and patient education for safe drug use.