Question

At low pH levels (e.g. stomach) is a weakly acidic drug mostly in its ionizable or non-ionizable form?

a) Ionizable
b) Non-ionizable
c) No specific form
d) Variable form

Answer 1

At low pH levels, such as those in the stomach, a weakly acidic drug is mostly in its non-ionizable form due to the high concentration of hydronium ions already present, which limits the drug's ability to donate hydrogen ions.

Step-by-step explanation:

At low pH levels such as those found in the stomach, a weakly acidic drug is mostly in its non-ionizable, or nonionized, form. We know that the pH of the stomach is strongly acidic, typically around 1-2.

In such an environment, weak acids tend to donate their hydrogen ions less readily because the concentration of hydronium ions is already high. The equilibrium favors the formation of the nonionized form of the acid, rather than its ionizable (ionized) counterpart.

Weak acids like acetic acid achieve an equilibrium in which most of the acid is present in their nonionized form and only a fraction is ionized at any given moment.

Given the high acidic pH of the stomach, we can infer that a weakly acidic drug will predominantly exist in its nonionized state due to the abundance of hydronium ions that are already present, making the environment less conducive for the acid to donate hydrogen ions and thus remain largely non-ionized.