The data shows filings peaked at 351 families in 2017 and fell to 170 by the most recent tracked year, with the 2022 midpoint of 217 confirming a gradual rather than sudden decline. This pattern is typical of a field where foundational mechanisms — matrix tablets, coating films, osmotic release — were claimed early and later filings increasingly compete for narrower improvements. It does not mean the technology has stopped being commercially relevant; it means the core claim space is already occupied, which pushes new filers toward incremental or adjacent claims. Readers should also account for publication lag: filings from the last 18 months are undercounted in any dataset with a mid-2026 cut-off.

US5639476A, covering controlled release formulations coated with aqueous dispersions of acrylic polymers, is the most-cited record in this corpus at 3,843 citations — more than double the next most-cited patent. Its age and citation count mean it is frequently cited by later filings that touch acrylic or similar polymer coating films for controlled release. Any freedom-to-operate search involving acrylic-based coating chemistry for oral or implantable dosage forms should expect this patent to appear as prior art. Its dominance also signals that coating-film chemistry, rather than being open ground, is one of the more thoroughly claimed corners of the field.

The IPC composition shows A61K (medicinal preparations) covering 11,384 of 11,399 records, while device-oriented classes like A61M (body fluid delivery devices) and A61F (implants) sit at 532 and 702 respectively — far thinner coverage relative to the corpus size. Polymer-specific classes such as C08G and C07D are thinner still. This gap suggests that device-integrated release mechanisms and specific polymer carrier chemistries are comparatively under-claimed relative to formulation chemistry itself, making them worth scoping before assuming the field is closed. Under-claimed does not mean unclaimed, so a targeted prior-art search in those specific subclasses is still necessary.

Momentum data in this dataset shows the most active assignees filing at very low volumes in the most recent year — often a single family, with year-over-year changes ranging from flat to declines of 67-100%. Co-assignee data shows the strongest collaborative relationship, at 115 shared families, links a university system with a specialist drug-delivery company, ahead of a university-hospital pairing at 73 and a pharma-to-pharma pairing at just 12. This pattern points to a field where sustained commercialisation often runs through university licensing to specialist delivery firms rather than large-scale in-house pharma R&D alone.

WO2006088305A1, filed by Chong Kun Dang Pharmaceutical Corp., claims a gastric-retentive mono-matrix tablet built from a hydrogel-forming combination of polyethylene oxide with a poloxamer or colloidal silica, plus a carbon dioxide-generating material that keeps the tablet floating in gastric fluid while releasing its active substance at a constant rate for at least two hours. A new design using a materially different flotation mechanism, a different hydrogel pairing, or a different release profile duration would likely sit outside this specific claim scope. However, any tablet relying on gas-generation-driven buoyancy combined with a PEO-based hydrogel matrix should be checked against this family specifically before finalising a formulation.