Distribution coefficients are values which describe the behavior of solutes in two immiscible liquids, and account for the total concentration of ionized and unionized drug in both the aqueous and organic phases . The distribution coefficient is often used to understand whether a drug is more hydrophilic (drawn to aqueous systems) or hydrophobic (drawn to organic or lipophilic systems). This in turn, helps predict the movement of the drug through the lipid bi-layer for absorption into the bloodstream. The distribution coefficient (logD) is defined as the ratio of the sum of concentrations of both charged and neutral species in the organic and aqueous phases. This differs from the partition coefficient (logP) since the latter only accounts for the ratio of neutral species in organic and aqueous phases. The differences can be seen below in Equation and Equation 2, describing the two quantities.