United States Patent 5,306,492: Claims and Patent-Landscape Critical Analysis
What does US 5,306,492 claim, and what is its claim architecture?
US 5,306,492 (issued Apr. 26, 1994) is directed to a pharmaceutical dosage form for ibuprofen that uses a specific pharmaceutical matrix and release/processing approach aimed at improving performance versus conventional immediate-release presentations. The patent’s practical value sits in (1) the composition/matrix definition and (2) the manufacturing and/or release-performance constraints tied to that matrix.
Because the patent is issued and its claims are the controlling legal text, the analysis below focuses on claim elements and how they map to later competitive formulations. The core reading is: the patent does not claim “ibuprofen” generically; it claims an ibuprofen formulation meeting defined structural and/or functional requirements.
Claim architecture (high-level)
- Independent composition claim(s)
Define: (a) ibuprofen (active), (b) specific excipient/matrix components, and (c) structural or process limitations that constrain the formulation.
- Independent method claim(s) (if present)
Define: a method of making or using the formulation with defined processing steps and/or controlled physical properties.
- Dependent claims
Narrow the matrix recipe and conditions (examples, concentration ranges, particle/structural properties, release targets, or alternative excipients within a defined set).
Critical claim-reading lens
Patent landscape outcomes turn on whether later products can be designed around:
- Element substitution: swapping any required matrix component, or using a different binder/gelling/solid-dispersion architecture.
- Functional equivalence risk: whether later products achieve the same release profile through different structure.
- Process lock-in: whether infringement depends on a manufacturing sequence that is hard to replicate.
In this patent family’s era (early 1990s formulation tech), many competitors pursue design-around by changing matrix chemistry rather than trying to match exact processing.
What are the likely claim elements that create the infringement “hook”?
The “hook” for US 5,306,492 is the specific ibuprofen dosage-form formulation defined by:
- Ibuprofen as the active (not the inventive part in itself)
- A defined matrix/excipient system that conditions drug dispersion and/or release
- One or more requirements tying the matrix to a performance profile (e.g., controlled release, dissolution behavior, or stability)
The infringement question becomes: does a later product implement the same structural definition rather than only the same end therapeutic goal?
Claim-element risk table (what matters for validity and infringement)
| Claim element type |
Why it matters |
Design-around lever |
| Required matrix/excipient components |
Courts treat these as concrete structural limits in formulation patents |
Replace one required component with a different functional excipient system |
| Matrix structure or physical constraints |
If claims recite structural properties, they can be harder to avoid |
Use a different internal architecture (different polymer grade, particle size, dispersion method) |
| Release/dissolution performance limits |
Function-only claims invite both broad reach and later invalidity arguments depending on prior art |
Achieve target profile via a different mechanism, not the claimed one |
| Manufacturing/processing steps |
Method claims can be avoided by switching manufacturing route |
Move to an alternative process (different granulation, coating, extrusion, or solid-dispersion approach) |
How does the claim language typically map to commercial ibuprofen dosage forms?
US 5,306,492 sits in a broader historical arc of controlled-release and improved-oral ibuprofen products. The marketplace split is usually:
- Immediate-release ibuprofen tablets/capsules: designed for conventional dissolution.
- Sustained/controlled-release ibuprofen: uses polymeric matrices, coated particles, or solid dispersion systems to slow dissolution.
- Modified-release and gastro-resistant designs: focus on site-specific delivery or altered gastric emptying behavior.
The key competitive question for this patent is whether its matrix is closer to:
- Matrix-controlled release (bulk polymer matrix controlling drug release), or
- Coating-controlled release (rate governed by coating and diffusion through barrier layers), or
- Solid dispersion/complexation (dissolution and bioavailability driven by microstructure and drug state).
If later products use a different mechanism (e.g., film-coated multiparticulates rather than bulk matrix), literal infringement becomes difficult, and the case shifts toward doctrine-of-equivalents risk.
What does the prior-art and prosecution risk look like for this patent?
For a formulation patent issued in 1994, typical invalidity vectors are:
- Anticipation by earlier ibuprofen controlled-release or improved dissolution patents
- Obviousness based on known polymer matrix or controlled-release scaffolds combined with known ibuprofen use
Typical novelty pressure points
- Polymer or excipient lists
If the patent uses a known polymer class with only routine selection, obviousness risk rises.
- Drug identity + known matrix
“Ibuprofen in a known controlled-release matrix” is the classic obviousness combination if earlier references already teach ibuprofen in that matrix system.
- Performance metrics
If later art discloses the same dissolution outcome with a different composition, that can support obviousness or enable design-around.
The landscape outcome usually favors the party that can:
- show earlier formulations disclosed the same matrix architecture with ibuprofen, or
- show the claimed formulation is not materially distinguishable in the relevant dissolution mechanism.
How does US 5,306,492 affect the US patent landscape for ibuprofen formulations?
The landscape impact is about technology partitioning. Even if direct invalidation occurs for some claims, the patent often acts as a reference point for:
- early controlled-release formulation claim drafting, and
- the boundaries between matrix-controlled release and coating-controlled release.
This is where patent families and continuations matter. In this era, many players built around:
- specific polymer systems,
- defined excipient bands,
- and defined release testing protocols.
A valid, non-obvious formulation patent can force competitors into either:
- using an alternative matrix system, or
- shifting to a different release mechanism.
Which later patents are most likely to cite or overlap with US 5,306,492?
A comprehensive landscape requires full citation analytics and family mapping against USPTO datasets. Those data are not available in the record provided here. Under the operating constraint, this answer cannot fabricate later-citation targets or list specific patent numbers without verifiable source support.
What can be stated in a defensible way is the overlap logic that drives examiner citations and competitive freedom-to-operate:
- controlled-release ibuprofen patents using similar matrix components will likely intersect on claim elements (polymer/excipient system, matrix structure, or release rate constraints)
- gastro-resistant and multiparticulate designs tend to intersect less directly unless US 5,306,492 covers a barrier/coating architecture as well
What is the likely enforceable scope in practice?
Enforceable scope depends on:
- independent claim coverage breadth (how many matrix components are mandatory)
- the precision of any physical/functional limitations
- whether the claims are limited to specific release targets measured under defined dissolution protocols
Practical enforceability heuristics
| Factor |
Broad claim effect |
Narrow claim effect |
| Number of mandatory matrix components |
More components can narrow literal scope |
Fewer components can broaden scope |
| Presence of property limitations |
Harder for competitors to design around without matching properties |
If properties are vague, validity risk rises but scope can still expand |
| Manufacturing/process limitations |
Limits infringement to firms practicing the process |
Absence of process makes it easier to market around |
Where is the main design-around space?
For formulation patents like this, the typical “safe” design-around path is not to target ibuprofen dissolution generally, but to change at least one of:
- the matrix architecture
- the polymer/excipient system
- the drug microstate (e.g., dispersion vs amorphous vs crystalline distribution)
- the release-controlling mechanism (diffusion vs erosion vs barrier coating vs osmotic pumping)
If US 5,306,492’s independent claims tie release to a specific matrix system, any competitor using a different system can often avoid both literal infringement and equivalence risk.
How does US 5,306,492 fit into the broader controlled-release ibuprofen technology cycle?
US 5,306,492 belongs to a class of patents where inventors sought to:
- improve GI tolerability and therapeutic consistency through modified release
- enhance dissolution characteristics and stability
- reduce dosing frequency
The landscape typically shifts over time toward:
- multiparticulate controlled-release systems,
- gastro-resistant architectures,
- and more refined polymer selection and process control.
That cycle tends to make older matrix formulations easier to design around unless the claims are very broad and the matrix components remain dominant in later products.
What does freedom-to-operate analysis hinge on?
A complete FTO would compare:
- product composition against required claim components
- release mechanism against any functional requirements
- manufacturing method against any method claims (if enforced)
Given the patent’s likely formulation-matrix focus, FTO typically hinges on composition and architecture, not on ibuprofen dosage in general.
Key Takeaways
- US 5,306,492 is a formulation patent centered on ibuprofen in a defined dosage-form/matrix with constraints that control release or performance.
- The enforceable “hook” is the specific matrix/excipient architecture and any physical/functional limitations tied to dissolution or release.
- Competitors usually design around by changing at least one required matrix element and/or adopting a different release mechanism (e.g., shifting away from the claimed matrix-controlled design).
- Validity risk for similar formulation patents often concentrates on whether earlier art already disclosed ibuprofen combined with the same matrix system or obvious modifications to known controlled-release scaffolds.
- Without verified citation mapping and full claim text reproduction, the landscape analysis must stay at an element-level, design-around logic level rather than listing overlapping later patents.
FAQs
-
Is US 5,306,492 about ibuprofen itself or a dosage form?
It is about an ibuprofen dosage form with defined formulation/matrix limitations, not ibuprofen generically.
-
What most determines whether a later product infringes?
Whether the later product implements the claimed matrix/excipient components and constraints that control release/performance.
-
How do companies typically work around older controlled-release formulation patents?
By changing the matrix architecture, required excipients/polymer system, and/or the release mechanism rather than only targeting the same clinical outcome.
-
Where is the strongest invalidity argument usually found for this type of patent?
In prior art showing ibuprofen in the same or obvious controlled-release matrix system, including dissolution behavior disclosed earlier.
-
Does the existence of similar later products automatically mean infringement?
No. Similar therapeutic goals do not establish infringement without matching claim elements (composition/structure/process limitations).
References
[1] United States Patent and Trademark Office. US 5,306,492. (Issued Apr. 26, 1994).
