An intrauterine device having at least one first pharmaceutically active ingredient and at least one first layer made of at least a first polymeric material, wherein between about 10 and about 60 v/v % of at least one particulate material is dispersed and/or incorporated in the first polymeric material. The presence of the particulate material will reduce the porosity of the polymer or otherwise obstruct the diffusion of the pharmaceutically active ingredient being released, thereby slowing its rate of release. In this way, it is possible to regulate the release rate and/or initial burst of the device, simply by adjusting the amount of particles/particulate material in the first layer, instead of having to adapt the size of the device to the desired release pattern, which requires expensive changes in production equipment and manufacturing processes.
