Page 14 - controlled drug delievery

Aqueous Solubility & Ionization constant (Contd)

• Most drugs are weak acids or weak bases.
• The aqueous solubility of the drug is highly dependent on the

relation between its pKa & the pH of the dissolution/ absorption
medium.
• Unionized form----------- low solubility & high permeability
• Ionized form------------ high solubility & low permeability
• Consider the formulation of a weak base for Oral SR formulation
with intended release duration of 8 hours?