Pharmacokinetics Flashcards
7 cards from real Pharmacy practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Pharmacokinetics flashcards as text
What does 'bioavailability' refer to in pharmacokinetics?
Answer: The fraction of an administered dose that reaches systemic circulation unchanged
Bioavailability is the fraction (F) of an administered dose that reaches the systemic circulation in unchanged form, making it available for therapeutic effect.
Which route of administration achieves 100% bioavailability?
Answer: Intravenous
Intravenous (IV) administration delivers drug directly into systemic circulation, bypassing all absorption barriers, and is the reference standard for 100% bioavailability.
The 'first-pass effect' primarily occurs in which organ?
Answer: Liver
The first-pass effect (presystemic metabolism) primarily occurs in the liver, where orally absorbed drugs are extensively metabolized before reaching systemic circulation, significantly reducing bioavailability.
Volume of distribution (Vd) is best defined as:
Answer: The theoretical volume needed to contain all drug at the observed plasma concentration
Vd is a theoretical (apparent) volume that relates the total amount of drug in the body to the measured plasma concentration; it does not correspond to a real physiological volume.
A drug with a high volume of distribution (Vd > 20 L/kg) is most likely:
Answer: Extensively distributed to peripheral tissues
A high Vd indicates the drug distributes widely outside the plasma into peripheral tissues (e.g., fat, muscle), resulting in low plasma concentrations relative to total body drug.
Which pharmacokinetic parameter describes the rate of drug elimination relative to drug concentration in plasma?
Answer: Clearance
Clearance (CL) is defined as the volume of plasma cleared of drug per unit time (mL/min or L/hr), and represents the body's efficiency at eliminating the drug.
The elimination half-life (t½) of a drug is mathematically related to which two pharmacokinetic parameters?
Answer: Volume of distribution and clearance
t½ = (0.693 × Vd) / CL; half-life is directly proportional to volume of distribution and inversely proportional to clearance, so either change will alter half-life.