Salts and Solubility

salts

used to enhance either lipid or water solubility of a drug molecule

-formed when an acid reacts with a base

charge of salts

electronically neutral (has positively charged cation + negatively charged anion)

HCl

strong acid

NaOH

strong base

inorganic salts

formed when inorganic acids or bases react with basic or acidic functional groups of drug molecules

inorganic salts of acidic drug molecules

commonly made using KOH, NaOH, Ca(OH)₂

inorganic salts of basic drug molecules

commonly made using HCl, HBr, H₂SO₄, H₃PO₄

inorganic salt form

enhances solvation, dissolution, and water solubility

positive & negative constituents not covalently bound

quickly dissociate

organic salts

products of reactions between drug molecules and acidic or basic compounds

water-soluble organic salts

increase solvation, dissolution, and water solubility of drug molecules

-commonly use sugars

lipid-soluble organic salts

decrease solvation, dissolution, and water solubility of drug molecules

-increase lipid solubility

identification of salt formation

if HCl or HBr acid not used, then “ic acid” → “ate”