Which characteristic is true of unionized drugs?

Unionized drugs are typically lipid soluble. This is an important characteristic because the lipid solubility of a drug affects its ability to cross biological membranes, such as the cell membrane, which is composed of a lipid bilayer. Unionized (or non-polar) forms of drugs can easily dissolve in lipids, allowing for efficient absorption in the body.

In contrast, hydrophilic or charged forms of drugs tend to be water soluble, which limits their ability to pass through lipid membranes. Therefore, when considering the behavior and absorption of drugs in biological systems, understanding the balance between the ionization of a drug and its lipid solubility is essential. Drugs that are unionized and lipid soluble can be effectively absorbed across membranes and reach target sites within the body.