Controlled release compositions (II)

DETAILED DESCRIPTION We claim: 1.
A controlled release composition comprising a prostaglandin and a polymeric carrier therefor comprising residues which are cross-linked through urethane groups, or analogues thereof, and which comprise polyethylene oxide having a ratio of number average molecular weight to functionality greater than 1,500, the degree of cross-linking being such that there is at least one cross-linking point per ten residues comprising the said polyethylene oxide but such that the proportion of the said polyethylene oxide is greater than 50% by weight of the polymeric carrier which, when prostaglandin-free, is a hydrogel in the dry form at 20.
degree.
C.
, contains crystalline regions, and exhibits syneresis in the wet form.
2.
A controlled release composition comprising a prostaglandin and a polymeric carrier therefor comprising residues which are cross-linked through urethane groups, or analogues thereof, and which comprise polyethylene oxide having a ratio of number average molecular weight to functionality greater than 1,500, the degree of cross-linking being such that there is at least one cross-linking point per ten residues comprising the said polyethylene oxide but such that the proportion of the said polyethylene oxide is greater than 50% by weight of the polymeric carrier which, in the presence of said prostaglandin, is a hydrogel in the dry form at 20.
degree.
C.
, contains crystalline regions, and exhibits syneresis in the wet form.
3.
The controlled release composition of claim 1, further comprising an additional drug other than a prostaglandin.
4.
The controlled release composition of claim 2, further comprising an additional drug other than a prostaglandin.
5.
The composition according to claim 1, wherein the polyethylene oxide has a ratio of number average molecular weight to functionality greater than 2,000.
6.
The composition according to claim 1, wherein the polyethylene oxide is the reaction product of a mixture comprising (i) an aliphatic or aromatic compound which is di-, tri- or tetra-substituted by at least one hydroxyl, carboxyl, amino or mercapto group with (ii) ethylene oxide