Final Exam Pharmacology
🧠 Objective 1.3: Explain how absorption, distribution, metabolism, and excretion affect
pharmacokinetics
Pharmacokinetics is the study of what the body does to a drug, and it involves four major
processes: absorption, distribution, metabolism, and excretion—often abbreviated as ADME.
Each phase influences the onset, intensity, and duration of a drug’s effect.
1. Absorption
● Definition: Movement of a drug from its site of administration into the bloodstream for
circulation.
● Factors affecting absorption (Lilley, 2024):
○ Route of administration: IV is immediate; oral drugs must dissolve and pass
through the GI tract.
○ Form of the drug: Enteric-coated and extended-release tablets delay absorption.
○ Blood flow to the absorption site: Greater perfusion = faster absorption.
○ Food presence: May enhance or inhibit absorption, depending on the drug.
○ Gastrointestinal motility & pH: Slower motility or altered pH can delay or
reduce absorption.
● Nursing implication: Monitor if a drug needs to be taken with food or on an empty
stomach for optimal absorption (ATI, 2023).
2. Distribution
● Definition: Movement of the absorbed drug through the bloodstream to tissues and
organs.
● Influencing factors (Lilley, 2024; Berman, 2021):
○ Blood flow to tissues: High perfusion organs (heart, liver, kidneys, brain) receive
drugs first.
, ○ Protein-binding: Many drugs bind to albumin; only unbound (free) drug is
active.
○ Tissue permeability: The blood-brain barrier and placental barrier restrict some
drugs.
● Nursing implication: Monitor serum albumin levels, especially in older adults or those
with liver disease, as hypoalbuminemia increases free drug → higher risk of toxicity.
3. Metabolism (Biotransformation)
● Definition: The enzymatic alteration of the drug, mostly in the liver, to prepare for
excretion.
● Key points (Lilley, 2024):
○ Involves cytochrome P450 (CYP450) enzymes.
○ May convert active drugs to inactive metabolites or produce active metabolites
from prodrugs.
○ First-pass effect: Oral drugs are metabolized in the liver before reaching
systemic circulation, which may reduce bioavailability.
○ Hepatic function and age influence metabolism.
● Nursing implication:
○ Assess liver function (e.g., AST, ALT).
○ Recognize that older adults and neonates may have slower metabolism → risk of
accumulation and toxicity.
4. Excretion
● Definition: Removal of drugs and their metabolites from the body, primarily via the
kidneys.
● Routes of excretion (Lilley, 2024; ATI, 2023):
, ○ Renal (urine): Main route; influenced by kidney function (GFR, creatinine
clearance).
○ Hepatic (bile → feces): Especially for lipid-soluble drugs.
○ Lungs: For volatile substances (e.g., anesthetics).
○ Other: Sweat, saliva, breast milk (especially important in lactating clients).
● Nursing implication:
○ Monitor renal labs (BUN, creatinine).
○ Adjust doses in clients with renal impairment to prevent drug accumulation and
toxicity.
🔁 Clinical Significance of ADME:
Each pharmacokinetic phase influences:
● How fast a drug takes effect (absorption)
● Where it goes in the body (distribution)
● How long it stays active (metabolism)
● How it is cleared from the body (excretion)
Understanding these processes helps nurses:
● Predict and monitor drug effects
● Recognize and prevent toxicity
● Optimize dosing and timing
● Educate patients about their medications
📚 Pharmacodynamics Defined
Pharmacodynamics is the study of what drugs do to the body, including how they exert their
therapeutic effects and how they interact with receptors.
, 🔑 The Role of Receptors in Pharmacodynamics
🔬 1. What Are Receptors?
● Receptors are specialized protein molecules located on the surface of or inside cells
(e.g., on membranes or within the cytoplasm or nucleus).
● Drugs produce effects by binding to receptors, much like a key fits into a lock.
● When a drug binds to a receptor, it may mimic, enhance, or block the body’s natural
chemical messengers (e.g., neurotransmitters, hormones).
🧪 2. Drug-Receptor Interaction Types
Type Description Example
Agonist Binds to a receptor and activates it to Albuterol (stimulates beta-2
produce a desired response. receptors to cause
bronchodilation)
Partial Agonist Produces a weaker response even Buprenorphine (used in opioid
when all receptors are occupied. addiction)
Antagonist Binds to a receptor but blocks or Naloxone (blocks opioid
inhibits its activation. receptors to reverse overdose)
Competitive Competes with agonists for receptor Beta blockers (e.g.,
Antagonist binding. Reversible by increasing metoprolol)
agonist concentration.
Noncompetitive Binds permanently or irreversibly to Aspirin (irreversibly inhibits
Antagonist receptors. Cannot be overcome by platelet COX enzyme)
increasing agonist.
🔁 3. Clinical Concepts of Receptor Activity
● Affinity: Strength of drug binding to a receptor
○ Higher affinity = stronger binding = more potent effect
● Efficacy: Ability of the drug to produce a maximal response
🧠 Objective 1.3: Explain how absorption, distribution, metabolism, and excretion affect
pharmacokinetics
Pharmacokinetics is the study of what the body does to a drug, and it involves four major
processes: absorption, distribution, metabolism, and excretion—often abbreviated as ADME.
Each phase influences the onset, intensity, and duration of a drug’s effect.
1. Absorption
● Definition: Movement of a drug from its site of administration into the bloodstream for
circulation.
● Factors affecting absorption (Lilley, 2024):
○ Route of administration: IV is immediate; oral drugs must dissolve and pass
through the GI tract.
○ Form of the drug: Enteric-coated and extended-release tablets delay absorption.
○ Blood flow to the absorption site: Greater perfusion = faster absorption.
○ Food presence: May enhance or inhibit absorption, depending on the drug.
○ Gastrointestinal motility & pH: Slower motility or altered pH can delay or
reduce absorption.
● Nursing implication: Monitor if a drug needs to be taken with food or on an empty
stomach for optimal absorption (ATI, 2023).
2. Distribution
● Definition: Movement of the absorbed drug through the bloodstream to tissues and
organs.
● Influencing factors (Lilley, 2024; Berman, 2021):
○ Blood flow to tissues: High perfusion organs (heart, liver, kidneys, brain) receive
drugs first.
, ○ Protein-binding: Many drugs bind to albumin; only unbound (free) drug is
active.
○ Tissue permeability: The blood-brain barrier and placental barrier restrict some
drugs.
● Nursing implication: Monitor serum albumin levels, especially in older adults or those
with liver disease, as hypoalbuminemia increases free drug → higher risk of toxicity.
3. Metabolism (Biotransformation)
● Definition: The enzymatic alteration of the drug, mostly in the liver, to prepare for
excretion.
● Key points (Lilley, 2024):
○ Involves cytochrome P450 (CYP450) enzymes.
○ May convert active drugs to inactive metabolites or produce active metabolites
from prodrugs.
○ First-pass effect: Oral drugs are metabolized in the liver before reaching
systemic circulation, which may reduce bioavailability.
○ Hepatic function and age influence metabolism.
● Nursing implication:
○ Assess liver function (e.g., AST, ALT).
○ Recognize that older adults and neonates may have slower metabolism → risk of
accumulation and toxicity.
4. Excretion
● Definition: Removal of drugs and their metabolites from the body, primarily via the
kidneys.
● Routes of excretion (Lilley, 2024; ATI, 2023):
, ○ Renal (urine): Main route; influenced by kidney function (GFR, creatinine
clearance).
○ Hepatic (bile → feces): Especially for lipid-soluble drugs.
○ Lungs: For volatile substances (e.g., anesthetics).
○ Other: Sweat, saliva, breast milk (especially important in lactating clients).
● Nursing implication:
○ Monitor renal labs (BUN, creatinine).
○ Adjust doses in clients with renal impairment to prevent drug accumulation and
toxicity.
🔁 Clinical Significance of ADME:
Each pharmacokinetic phase influences:
● How fast a drug takes effect (absorption)
● Where it goes in the body (distribution)
● How long it stays active (metabolism)
● How it is cleared from the body (excretion)
Understanding these processes helps nurses:
● Predict and monitor drug effects
● Recognize and prevent toxicity
● Optimize dosing and timing
● Educate patients about their medications
📚 Pharmacodynamics Defined
Pharmacodynamics is the study of what drugs do to the body, including how they exert their
therapeutic effects and how they interact with receptors.
, 🔑 The Role of Receptors in Pharmacodynamics
🔬 1. What Are Receptors?
● Receptors are specialized protein molecules located on the surface of or inside cells
(e.g., on membranes or within the cytoplasm or nucleus).
● Drugs produce effects by binding to receptors, much like a key fits into a lock.
● When a drug binds to a receptor, it may mimic, enhance, or block the body’s natural
chemical messengers (e.g., neurotransmitters, hormones).
🧪 2. Drug-Receptor Interaction Types
Type Description Example
Agonist Binds to a receptor and activates it to Albuterol (stimulates beta-2
produce a desired response. receptors to cause
bronchodilation)
Partial Agonist Produces a weaker response even Buprenorphine (used in opioid
when all receptors are occupied. addiction)
Antagonist Binds to a receptor but blocks or Naloxone (blocks opioid
inhibits its activation. receptors to reverse overdose)
Competitive Competes with agonists for receptor Beta blockers (e.g.,
Antagonist binding. Reversible by increasing metoprolol)
agonist concentration.
Noncompetitive Binds permanently or irreversibly to Aspirin (irreversibly inhibits
Antagonist receptors. Cannot be overcome by platelet COX enzyme)
increasing agonist.
🔁 3. Clinical Concepts of Receptor Activity
● Affinity: Strength of drug binding to a receptor
○ Higher affinity = stronger binding = more potent effect
● Efficacy: Ability of the drug to produce a maximal response
