Which term best describes the order of absorption in Fick's framework when rate is proportional to a concentration term?

Which term best describes the order of absorption in Fick's framework when rate is proportional to a concentration term?

• A. Zero order
• B. First order
• C. Mixed order
• D. Dependent order

Answer: (B)

The concept is first-order absorption. When the rate of transfer is proportional to a concentration term, the amount absorbed per unit time scales with how much drug is present for absorption, so the rate decreases as the concentration term declines. In Fick's framework, this gives dA/dt ∝ C, meaning a constant fraction of the available drug is absorbed per unit time. This is typical for GI absorption, where the concentration driving the transfer drops as absorption proceeds. Zero-order would be a constant amount absorbed per time regardless of concentration, which isn’t the case here; mixed or other nonstandard orders aren’t describing this simple proportional relationship.

The concept is first-order absorption. When the rate of transfer is proportional to a concentration term, the amount absorbed per unit time scales with how much drug is present for absorption, so the rate decreases as the concentration term declines. In Fick's framework, this gives dA/dt ∝ C, meaning a constant fraction of the available drug is absorbed per unit time. This is typical for GI absorption, where the concentration driving the transfer drops as absorption proceeds. Zero-order would be a constant amount absorbed per time regardless of concentration, which isn’t the case here; mixed or other nonstandard orders aren’t describing this simple proportional relationship.