Pharmacokinetic Principles Flashcards
7 cards from real Pharmacology practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Pharmacokinetic Principles flashcards as text
Which of the following best describes the concept of clearance in pharmacokinetics?
Answer: The volume of plasma cleared of drug per unit time
Clearance (CL) is defined as the volume of plasma from which a drug is completely removed per unit time.
A weakly acidic drug (pKa 4.5) is administered. In which compartment will it be most ionized?
Answer: Blood (pH 7.4)
A weak acid is most ionized in alkaline environments; blood at pH 7.4 causes greater ionization relative to gastric acid.
Which pharmacokinetic principle explains why alkalinizing urine increases renal elimination of salicylates in overdose?
Answer: Ion trapping — ionized drug cannot be reabsorbed
Ion trapping: alkaline urine ionizes the weak acid salicylate, preventing tubular reabsorption and increasing urinary excretion.
A drug follows first-order kinetics. If the initial plasma concentration is 100 mg/L and the half-life is 4 hours, what is the approximate concentration after 12 hours?
Answer: 12.5 mg/L
After 3 half-lives (12 hours), concentration falls by 50% three times: 100→50→25→12.5 mg/L.
Which cytochrome P450 enzyme is responsible for metabolizing the greatest number of clinically used drugs?
Answer: CYP3A4
CYP3A4 metabolizes approximately 50% of all clinically used drugs and is the most abundant hepatic CYP enzyme.
Therapeutic drug monitoring is MOST important for drugs with:
Answer: Narrow therapeutic index and variable pharmacokinetics
Drugs with a narrow therapeutic index and unpredictable pharmacokinetics require monitoring to avoid toxicity or subtherapeutic levels.
Which of the following is an example of Phase II drug metabolism?
Answer: Glucuronide conjugation
Phase II reactions involve conjugation (glucuronidation, sulfation, acetylation) to increase drug polarity for excretion.