The four primary processes of pharmacokinetics are absorption, distribution, metabolism, and excretion.
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excretion
These four processes describe how the body handles a drug from entry to elimination.
Question 2
Pharmacodynamics refers to what the drug does to the body.
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pharmacodynamics
Pharmacodynamics examines the relationship between drug concentrations at the site of action and the resulting effects on the body.
Question 3
Pharmacokinetics refers to what the body does to the drug.
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pharmacokinetics
Understanding pharmacokinetics helps the nurse understand a drug's actions, dosing frequency, interactions, and precautions.
Question 4
Bioavailability refers to the amount of active drug that enters systemic circulation and is available at the site of action.
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bioavailability
IV medications are 100% bioavailable because there are no barriers to absorption. Oral medications have lower bioavailability due to multiple absorption barriers.
Question 5
The half-life of a drug is the amount of time it takes for the serum concentration to reduce by 50%.
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half-life
Half-life determines dosing frequency. It takes approximately five half-lives for a drug to be functionally eliminated from the body.
Question 6
First-pass metabolism occurs primarily in the liver when oral drugs are absorbed and transported via the portal venous system.
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liver
Liver enzymes transform the drug into metabolites before it reaches systemic circulation, which can decrease bioavailability.
Question 7
The primary site for cytochrome P450 enzyme activity in drug metabolism is the liver.
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liver
CYP enzymes metabolize primarily lipid-soluble drugs. Clients with liver disease may have decreased metabolic activity.
Question 8
Only the free or unbound portion of a drug can act at its target receptor sites.
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free
Drugs bound to plasma proteins like albumin cannot cross cell membranes or interact with receptors until they are released from the binding site.
Question 9
It takes approximately five half-lives for a drug to be considered functionally eliminated from the body.
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five
After five half-lives, approximately 97% of the drug has been eliminated from the body.
Question 10
The blood-brain barrier is a protective system that prevents many drugs from entering the central nervous system.
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blood-brain barrier
Lipid-soluble drugs and those poorly bound to proteins can cross the barrier, but many antimicrobials and chemotherapy drugs cannot.
Question 11
Drugs administered intravenously are immediately 100% bioavailable because there are no barriers to absorption.
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bioavailable
IV administration bypasses all absorption barriers, delivering the full dose directly into the bloodstream.
Question 12
The most vascular organs receiving the most blood supply are the heart, liver, kidneys, and brain.
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vascular
Drug concentrations are highest in well-perfused organs. Less vascular areas like adipose tissue, skin, and bone receive lower drug concentrations.
Question 13
Aspartate transaminase (AST) and alanine transaminase (ALT) are liver enzymes monitored to detect hepatic dysfunction.
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ALT
Elevated AST and ALT levels may indicate liver damage, which can affect drug metabolism and increase the risk of toxicity.
Question 14
Blood urea nitrogen (BUN) and serum creatinine are used to assess kidney function before administering renally excreted drugs.
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creatinine
Renal disorders may increase a drug's duration of action, requiring dosage adjustments to prevent accumulation and toxicity.
Question 15
The therapeutic index is the ratio between a drug's toxic dose and its therapeutic dose.
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therapeutic index
A narrow therapeutic index means there is a small margin between an effective dose and a toxic dose, requiring careful monitoring.
Question 16
Gentamicin is 0% bioavailable when taken orally because it is not absorbed by the small intestine.
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orally
Gentamicin must be given intramuscularly or intravenously. It is well absorbed via IM injection and 100% bioavailable via IV.
Question 17
Absorption of oral medications can be affected by the presence of food in the gut.
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food
Food may slow, speed up, or reduce drug absorption depending on the drug. Some medications must be taken on an empty stomach for proper absorption.
Question 18
The adenosine antidysrhythmic medication has a half-life of less than 10 seconds.
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adenosine
This extremely short half-life means adenosine clears the bloodstream almost immediately, while amiodarone has a half-life of roughly 100 days.
Question 19
The small intestine is the primary site of absorption for most oral medications due to its large surface area from mucosal villi and microvilli.
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small, intestine
The villi and microvilli dramatically increase surface area, allowing more rapid and complete absorption compared to the stomach.
Question 20
Lipid-soluble drugs are distributed more widely throughout the body than water-soluble drugs.
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lipid-soluble
Lipid-soluble drugs can rapidly cross cellular membranes due to the lipid nature of cell membranes, reaching more tissue compartments.