FREE Pharmacology Pharmacokinetics Questions and Answers
Which of the following processes is primarily responsible for the movement of a drug from its site of administration into the bloodstream?
Absorption refers to the process by which a drug enters the bloodstream from its site of administration. This is a critical step for oral medications, as the drug must cross biological membranes to reach systemic circulation.
The term "bioavailability" refers to:
Bioavailability measures the proportion of a drug that enters systemic circulation unchanged and is available for action. It is especially important for oral drugs, which undergo first-pass metabolism.
Which organ is most responsible for the metabolism of drugs?
The liver is the primary organ for drug metabolism, where enzymes (mainly in the cytochrome P450 family) convert drugs into more water-soluble forms for excretion.
What does "first-pass metabolism" refer to?
First-pass metabolism occurs when a drug is significantly metabolized in the liver after oral absorption but before it reaches systemic circulation, reducing its bioavailability.
A drug with a half-life of 4 hours will have approximately 25% of the initial dose remaining in the body after:
The half-life of a drug is the time it takes for its plasma concentration to reduce by half. After 4 hours (one half-life), 50% remains; after 8 hours (two half-lives), 25% remains.