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Quizzes > Health & Medicine

Pharmacokinetics Test: Practice Questions on ADME Basics

Quick ADME practice quiz with instant answers to check your understanding.

Editorial: Review CompletedCreated By: Desh Kae Sache HalatUpdated Aug 23, 2025
Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art pharmacology quiz pharmacokinetics drug absorption distribution metabolism on dark blue background

This pharmacokinetics test helps you practice ADME-absorption, distribution, metabolism, and excretion-and check what you know before an exam. Work through short, exam-style questions with instant answers to learn as you go. For more practice, try our pharmacology quiz for nurses or review pharmacy board exam questions.

What term describes the fraction of an orally administered drug that reaches the systemic circulation unchanged?
Clearance
Volume of distribution
Bioavailability
Half-life
Bioavailability refers to the percentage of an orally administered dose that reaches systemic circulation intact, reflecting absorption and first-pass metabolism. It is crucial for dosing decisions. High first-pass effect reduces bioavailability significantly, requiring dose adjustments to achieve therapeutic levels.
What process describes the initial metabolism of a drug by the liver after oral administration?
Phase II conjugation
Zero-order metabolism
First-pass effect
Enterohepatic recirculation
The first-pass effect describes the metabolism of a drug in the liver immediately after absorption from the gut and before reaching systemic circulation. This can greatly reduce the active drug concentration. Drugs with high first-pass metabolism often require alternative routes or higher oral doses.
Which mechanism is the primary method by which most drugs cross cell membranes?
Facilitated diffusion
Endocytosis
Passive diffusion
Active transport
Most small, lipophilic drugs cross cell membranes by passive diffusion down their concentration gradient. This process does not require energy or transport proteins. Active or facilitated transport is reserved for specific drugs or molecules.
In the one-compartment model, what assumption is made about the distribution of a drug?
Two distinct distribution phases
Instant distribution into a single homogenous compartment
Sequential organ-specific distribution
Slow equilibrium between compartments
The one-compartment model assumes the drug instantaneously distributes evenly throughout a single, homogenous compartment. This simplifies pharmacokinetic calculations by treating the body as a uniform space. It is a basic model and may not apply to drugs with complex distribution patterns.
The volume of distribution (Vd) is best described as:
The volume of extracellular fluid only
The physical volume of blood in the body
The volume of urine produced per day
The theoretical volume necessary to contain the total drug amount at the same concentration as plasma
Volume of distribution is a theoretical volume that relates the drug dose to the plasma concentration, showing how extensively a drug disperses into tissues. A large Vd indicates extensive tissue binding or uptake. It is not a real physiological volume but a calculation tool.
What is the definition of elimination half-life (t1/2) of a drug?
Time for the dose to reduce by 25%
Time to reach peak plasma concentration
Time to eliminate all the drug from the body
Time taken for plasma concentration to decrease by 50%
Elimination half-life is the time required for the plasma concentration of a drug to fall by half. It is key for determining dosing intervals and steady-state accumulation. Different drugs have varied half-lives based on their clearance and distribution.
Which parameter represents the volume of plasma cleared of drug per unit time?
Half-life
Clearance
Bioavailability
Volume of distribution
Clearance defines the volume of plasma from which the drug is completely removed per unit time, indicating elimination efficiency. It incorporates hepatic and renal contributions. Clearance is crucial for calculating maintenance dosing.
Tmax refers to:
Half-life of the drug
Total clearance time
Maximum plasma concentration achieved
Time to reach maximum plasma concentration after drug administration
Tmax is the time point at which the peak plasma concentration (Cmax) is attained after a dose. It helps assess the rate of absorption of a drug. Faster absorption yields an earlier Tmax.
A 500 mg IV dose results in a plasma concentration of 10 mg/L. What is the volume of distribution (Vd)?
10 L
500 L
50 L
5 L
Vd is calculated by dividing dose by plasma concentration: 500 mg / 10 mg/L = 50 L. This reflects the apparent space in the body into which the drug distributes. A higher Vd suggests extensive tissue uptake.
A drug highly bound to plasma proteins will typically:
Undergo zero-order kinetics
Be cleared faster
Have a lower volume of distribution compared to a drug with low protein binding
Have a higher volume of distribution
Protein-bound drugs remain in the vascular compartment, reducing the apparent volume of distribution. Only unbound drug can distribute into tissues. This binding also influences drug clearance and free drug levels.
Which kinetic order is characterized by a constant fraction of drug eliminated per unit time?
Zero-order kinetics
First-order kinetics
Michaelis-Menten kinetics
Mixed-order kinetics
First-order kinetics means the rate of elimination is proportional to drug concentration, so a constant fraction is removed each time period. Most drugs follow this at therapeutic doses. In contrast, zero-order clears a constant amount, not fraction.
Michaelis-Menten kinetics apply when:
Elimination is always proportional to concentration
Absorption is the rate-limiting step
Elimination enzymes become saturated at high drug concentrations
Distribution is instantaneous
Michaelis-Menten kinetics describe saturable processes where elimination rate plateaus at high concentrations when enzymes are fully occupied. Small increases in dose can lead to disproportionate concentration rises. Drugs like phenytoin exhibit this behavior.
Phase II metabolism typically involves:
Reduction in the gut flora
Oxidation by CYP450 enzymes
Removal of functional groups
Conjugation reactions such as glucuronidation
Phase II metabolism adds endogenous substrates (e.g., glucuronic acid) to make drugs more water soluble for excretion. This conjugation follows Phase I modifications or can occur directly. It usually yields inactive metabolites.
A weak acid drug will be most non-ionized in the:
Blood (pH ~7.4)
Urine (variable pH)
Small intestine (higher pH)
Stomach (low pH)
Weak acids remain largely non-ionized in acidic environments like the stomach, facilitating passive diffusion across membranes. In more alkaline settings, they ionize and are less lipid-soluble. This pH partitioning influences absorption and distribution.
The term AUC represents:
Absolute uptake capacity
Absorption uniformity coefficient
Area under the plasma concentration - time curve
Average urinary clearance
AUC measures total drug exposure over time by integrating plasma concentration against time. It is directly proportional to the dose and inversely related to clearance. AUC is used to compare bioavailability between formulations.
The extraction ratio (E) of an organ is defined as:
Amount excreted / Amount administered
(Arterial concentration - Venous concentration) / Arterial concentration
Urinary clearance / Renal blood flow
Venous concentration / Arterial concentration
Extraction ratio quantifies the fraction of drug removed by an organ in one pass, calculated from arterial minus venous drug levels over arterial level. High extraction organs like the liver remove drugs efficiently. It influences hepatic clearance.
Calculate clearance if Vd = 40 L and t1/2 = 4 hours.
7.5 L/hour
40 L/hour
0.693 L/hour
6.93 L/hour
Clearance can be derived from half-life and volume of distribution: CL = (0.693 × Vd) / t1/2 = (0.693 × 40) / 4 = 6.93 L/hour. This links kinetic parameters for dosing strategies. Accurate clearance estimates guide infusion rates.
Enterohepatic recirculation leads to:
Increased total clearance
Prolonged drug half-life
Reduced bioavailability
Decreased half-life
Enterohepatic recirculation occurs when drug excreted in bile is reabsorbed from the intestine, extending its presence in the body. This can create secondary peaks in plasma concentration - time curves and prolong half-life. Recognizing it is key for interpreting PK data.
A prodrug requiring CYP450 activation means:
It is inactive until metabolized by liver enzymes into an active form
It bypasses hepatic metabolism altogether
It is active immediately and inactivated by CYP450
It is exclusively excreted unchanged
Prodrugs are designed to improve properties like solubility or absorption and rely on enzymatic conversion (often via CYP450) to become active. Without this activation, they would remain pharmacologically inert. Clinicians must consider enzyme variability.
Co-administration of a CYP3A4 inhibitor will:
Increase renal clearance of substrates
Increase plasma concentration of CYP3A4 substrate drugs
Have no effect on substrate levels
Decrease plasma concentration of substrate drugs
CYP3A4 inhibitors slow the metabolism of drugs that are substrates for that enzyme, leading to higher plasma concentrations and potential toxicity. Dose adjustments or alternative therapies may be needed. Understanding enzyme interactions prevents adverse effects.
Phenytoin exhibits non-linear kinetics because:
It is 100% protein bound
It is eliminated exclusively by the kidneys
Its metabolism follows saturable (zero-order) kinetics at therapeutic concentrations
It undergoes rapid first-pass metabolism
Phenytoin demonstrates saturable metabolism, so small dose increases can cause disproportionate plasma level rises once metabolic enzymes are saturated. This zero-order elimination makes dosing challenging. Monitoring levels is essential.
In a two-compartment model, the beta phase represents:
The initial rapid distribution phase
The time to reach steady state
The absorption phase
The elimination phase following distribution equilibrium
In two-compartment kinetics, the alpha phase reflects rapid drug distribution between central and peripheral compartments. The beta phase follows when equilibrium is reached and elimination predominates. This model explains biexponential decline curves.
To maintain a steady-state concentration, the maintenance dose rate equals:
Dose/AUC
Bioavailability × Clearance
Volume of distribution × Half-life
Clearance × Desired plasma concentration
At steady state, the rate of drug administration equals the rate of elimination. Maintenance dose rate is calculated by multiplying clearance by the target plasma concentration. This ensures consistent therapeutic levels.
Ultra-rapid CYP2D6 metabolizers taking codeine are at risk of:
Hyperglycemia
Reduced analgesic effect
Increased morphine levels leading to toxicity
No conversion to active drug
CYP2D6 ultra-rapid metabolizers convert codeine to morphine more quickly and completely, risking opioid toxicity even at standard doses. Genetic testing can identify at?risk patients. Personalized dosing improves safety.
Induction of CYP enzymes by rifampin will:
Have no effect on AUC
Decrease AUC of co-administered drugs metabolized by those enzymes
Increase half-life of substrates
Increase AUC of those drugs
Rifampin induces several CYP enzymes, accelerating the metabolism of co-administered drugs and reducing their area under the curve. This often necessitates dose increases of affected drugs to maintain efficacy. Monitoring levels prevents therapeutic failures.
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Study Outcomes

  1. Define Key Pharmacokinetic Processes -

    Understand the basic principles of absorption, distribution, metabolism, and elimination and how they influence drug behavior in the body.

  2. Interpret Drug Absorption and Bioavailability -

    Evaluate factors affecting oral and intravenous absorption and calculate bioavailability to optimize dosing strategies.

  3. Calculate Pharmacokinetic Parameters -

    Perform calculations for half-life, clearance, and volume of distribution to predict drug concentration over time.

  4. Differentiate Elimination Pathways -

    Distinguish between hepatic metabolism and renal excretion and their impact on drug clearance.

  5. Analyze Concentration-Time Profiles -

    Interpret Cmax, Tmax, and area under the curve (AUC) from pharmacokinetic graphs to assess drug exposure.

  6. Apply Pharmacokinetics to Exam Questions -

    Tackle pharmacology exam and pharm quiz questions with confidence by integrating core PK concepts and problem-solving techniques.

Cheat Sheet

  1. LADME Mnemonic -

    Use the LADME sequence (Liberation, Absorption, Distribution, Metabolism, Elimination) to recall each pharmacokinetic phase in order, as recommended by university pharmacology syllabi. Mnemonic tricks like "LADME Loves Awesome Drug Mastery Everyday" make it stick during a pharmacology exam. This structure underpins many drug absorption quiz and pharmacokinetics questions.

  2. Bioavailability (F) & First-Pass Effect -

    Bioavailability (F) equals (AUCpo/AUCiv)×(Doseiv/Dosepo), a key pharmacokinetics formula found in Goodman & Gilman's textbook and FDA guidance. Remember that high hepatic extraction (E) reduces F via first-pass metabolism, so F=1 - E. This concept often appears in pharm quizzes on drug absorption and systemic availability.

  3. Volume of Distribution (Vd) -

    Volume of distribution is Vd=Amount in body (mg)/Plasma concentration (mg/L), as outlined in clinical pharmacology journals (e.g., NCBI). A large Vd suggests extensive tissue binding (lipophilicity), whereas a small Vd implies confinement to plasma. Mastering Vd helps you interpret distribution patterns in pharmacology quizzes.

  4. Clearance (Cl) & Half-Life (t½) -

    Total clearance, Cl=Rate of elimination/Cp, and half-life, t½=0.693×(Vd/Cl), are core equations in pharmacokinetics questions from academic sources like Katzung. Faster Cl shortens t½, meaning more frequent dosing is needed to maintain therapeutic levels. Knowing these relationships boosts your confidence on drug elimination sections of a pharmacology exam.

  5. First-Order vs. Zero-Order Kinetics -

    Most drugs follow first-order kinetics where rate ∝ concentration, but some (e.g., ethanol, phenytoin) exhibit zero-order elimination at high doses, giving a constant rate. Recognizing which kinetics applies affects dosing and accumulation - critical for elimination questions. This distinction is a favorite in pharmacology quizzes and prep resources at major universities.

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