What aging-related change most commonly reduces drug effectiveness?

What aging-related change most commonly reduces drug effectiveness?

• A. Increased hepatic blood flow
• B. Decreased metabolism
• C. Increased renal clearance
• D. Enhanced first-pass metabolism

Answer: (B)

Aging commonly slows hepatic metabolism because the liver mass and blood flow decline, and phase I oxidative reactions become less active. When a drug must be metabolized to an active form to exert its effect (a prodrug or a drug whose active form depends on metabolism), this reduced metabolic activity leads to less formation of the active metabolite and therefore a weaker therapeutic effect. For drugs that are active in their original form, decreased metabolism may actually raise levels and toxicity, but the scenario described asks about reduced effectiveness due to aging, which fits the diminished activation pathway. The other options don’t fit as well: aging typically does not increase hepatic blood flow or renal clearance; renal function often declines, which would tend to raise drug exposure rather than reduce effectiveness. Enhanced first-pass metabolism is not the common aging change observed.

Aging commonly slows hepatic metabolism because the liver mass and blood flow decline, and phase I oxidative reactions become less active. When a drug must be metabolized to an active form to exert its effect (a prodrug or a drug whose active form depends on metabolism), this reduced metabolic activity leads to less formation of the active metabolite and therefore a weaker therapeutic effect. For drugs that are active in their original form, decreased metabolism may actually raise levels and toxicity, but the scenario described asks about reduced effectiveness due to aging, which fits the diminished activation pathway.

The other options don’t fit as well: aging typically does not increase hepatic blood flow or renal clearance; renal function often declines, which would tend to raise drug exposure rather than reduce effectiveness. Enhanced first-pass metabolism is not the common aging change observed.