PCL102H1 Lecture Notes - Lecture 11: Partition Coefficient
27 Apr 2016
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Document Summary
Physicochemical properties of drugs affecting permeability and distribution: molecular size. Most drugs have molecular weight between 200-500 mmol: solubility in water and lipid phases. Ability of a solute to dissolve in a solvent to form a homogenous solution. Lipophilicity is a key physical property of a drug and determines its membrane permeability. Solubility/permeability of drug is largely dependent on functional r groups on drug molecule and classification of chemical bonds: Non-covalent (ionic, hydrogen, hydrophobic interactions, van der waals) Drugs have both polar and non-polar groups and it"s the combination of these which determines their solubility in vivo. Partition coefficient (kow) solubility in lipid / solubility in water. Low kow low lipid solubility, poor ability to cross membrane. Absorption is more likely if drug doesn"t violate more than one of these rules. Lipophilicity is high, but not too high: pow < 5. # functional groups that can donate hydrogen atoms to form hydrogen bonds <5.
