| abstract |
There is provided a controlled release formulation including an inner core comprising, or coated with, a drug, which drug possesses (a) a free acid group which can be converted into an alkali metal salt and (b) a pKa in the rnage 2.0 to 9.0, which inner core is subsequently coated with a rate-controlling membrane that determines drug release, wherein the drug is present as a salt that displays higher solubility at pH 4.5 to 8.0 than the corresponding compound containing a free acid group. |