The device is a container at least part of whose wall is of semi-permeable membrane material and has in its wall at another posn. at least one hole forming a channel of predetermined bore. The container is filled with an active agent in soln., or a solid which is soluble in the external fluids from the body cavity etc., or finely divided in suspension in an org. or mineral soln.; in all cases the contents are such that they have a negative osmotic press. gradient relative to the fluids in the ambient mixt., which therefore migrate through the membrane and produce an internal press. expelling the contents through the channel(s) at a constant dose rate which may be preset either by the osmotic press. balance and orifice dimensions alone or by the removal to a predetermined extent of an impermeable sheath over the membrane's exterior. The material used for the membrane is esp. cellulose acetate. Esp. suitable for use in gastro-intestinal and gynaecological tracts or eye-sockets etc. May also be used for agricultural or horticultural dosage e.g., with fertilisers, herbicides, algicides, fungicides, etc.
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