Bioavailability refers to the fraction of an administered substance that reaches the systemic circulation and is available for action. Polarity affects bioavailability by influencing the absorption of substances across cell membranes. Lipophilic compounds, due to their nonpolar nature, can easily diffuse across the lipid bilayers of cell membranes, potentially leading to higher bioavailability. Conversely, polar compounds may require specific transport mechanisms to cross membranes, which can limit their bioavailability.
