A controlled release bead comprises: (i) a core unit of a substantially water-soluble
or water-swellable inert material; (ii) a first layer on the core unit of a substantially
water-insoluble polymer; (iii) a second layer covering the first layer and containing
an active ingredient; and (iv) a third layer of polymer on the second layer effective
for controlled release of the active ingredient, wherein the first layer is adapted
to control water penetration into the core. A method of producing the controlled
release bead is also disclosed.
