DOSAGE FORM FOR DELIVERING ACID SENSITIVE BENEFICIAL AGENT

A dosage form (20) comprises (a) a compartment (26) formed by a first wall (25) and a second wall (26). with the first wall surrounding and facing the inside of the compartment and the second wall surrounding the first wall and facing the environment of use; (b) a beneficial agent formulation (27) in the compartment (26) (c) at least one passageway (23) through the walls (22) for dispensing the beneficial agent formulation (27) from the dosage form to the environment of use over time; characterised in that the agent formulation forms with fluid that enters the compartment a fluid environment exhibiting a pH less than 5; (d) the first wall (25) permits the passage of fluid and comprises means for keeping its structural integrity in a first fluid environment exhibiting a pH less than 5 and for losing its structural integrity in a second fluid environment exhibiting a pH greater than 5; and (e) the second wall (24) permits the passage of fluid and comprises means for keeping its structural integrity in a first fluid environment exhibiting a pH less than 5 and for keeping its structural integrity in a second environment exhibiting a pH greater than 5. t