What effect does altering pH have on ionizable drugs?

Altering pH has a significant impact on ionizable drugs primarily because it can influence both their solubility and absorption. Drugs can exist in ionized or non-ionized forms depending on the pH of their environment and the pKa of the drug. The ionized form of a drug is often more soluble in water, while the non-ionized form is generally more permeable across biological membranes, which facilitates absorption.

When the pH is adjusted in the environment where the drug is administered, it can shift the balance between these two forms. For instance, a weak acid drug will become more ionized in a more basic (alkaline) environment, potentially decreasing its lipid solubility and, therefore, its absorption into the bloodstream. Conversely, in an acidic environment, it may exist in a more non-ionized, lipid-soluble form, leading to better absorption.

Thus, modifying the pH can directly affect the pharmacokinetic properties of the drug, including its solubility and the extent of absorption, making option A the correct choice in this context.