Practice Test GeeksABT - American Board of Toxicology Practice Test
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Toxicokinetics and Metabolism Flashcards

6 cards from real ABT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. Which pharmacokinetic parameter describes the fraction of an administered dose that reaches systemic circulation unchanged?

    Answer: Bioavailability (F)

    Bioavailability (F) is the fraction of an administered dose that reaches the systemic circulation unchanged, accounting for absorption and first-pass metabolism.

  2. Which cytochrome P450 enzyme is responsible for metabolizing the largest number of pharmaceutical drugs (approximately 30–40%)?

    Answer: CYP3A4

    CYP3A4 is the most abundant hepatic and intestinal CYP enzyme and metabolizes approximately 30–40% of clinically used drugs, making it a key site of drug-drug interactions.

  3. A chemical with a high volume of distribution (Vd > 10 L/kg) is most likely to be:

    Answer: Highly lipophilic and distributed into peripheral tissues

    A high volume of distribution indicates the drug is extensively distributed into peripheral tissues (fat, muscle), suggesting high lipophilicity or strong tissue protein binding.

  4. First-order elimination kinetics means that:

    Answer: The rate of elimination is directly proportional to the drug concentration

    In first-order kinetics, a constant fraction (not amount) of drug is eliminated per unit time; the rate of elimination is proportional to drug concentration, resulting in a constant half-life.

  5. The hepatic extraction ratio (ER) of a drug determines whether its clearance is sensitive to changes in:

    Answer: Hepatic blood flow for high-ER drugs and protein binding for low-ER drugs

    High extraction ratio (ER > 0.7) drugs have flow-limited clearance sensitive to hepatic blood flow, while low ER drugs (< 0.3) have capacity-limited clearance sensitive to enzyme activity and protein binding.

  6. Which phase II biotransformation reaction is most important for detoxifying reactive electrophilic metabolites via conjugation with a tripeptide?

    Answer: Glutathione conjugation (GST)

    Glutathione S-transferases (GSTs) conjugate reactive electrophilic metabolites with glutathione (γ-Glu-Cys-Gly), detoxifying them and preventing cellular damage.