Which of the following is a factor that determines the rate of elimination?

• A. Enzymes in the gut and bloodstream
• B. Blood type
• C. Eye color
• D. Time since last dose

Answer: (C)

Elimination rate is determined by how quickly the body metabolizes and clears a drug. Enzymes in the gut and bloodstream can break down drugs before they reach systemic circulation or while they’re circulating, shaping how fast the drug is eliminated from the body. Eye color and blood type don’t influence drug metabolism or clearance. Time since the last dose affects the current level of drug at a moment in time, but it doesn’t set the intrinsic speed of elimination. In pharmacokinetics, factors like enzyme activity and organ function (liver, kidneys) govern how fast a drug is eliminated, and those gut- and blood-borne enzymes are a real piece of that process.