US Patent 6,599,531 Landscape: What Do the Claims Cover for Ibuprofen + Hydrocodone Bitartrate Tablets?
What is US 6,599,531 claiming at the core?
US 6,599,531 claims a pharmaceutical tablet composition and a corresponding wet-granulation method for making tablets that combine:
- Ibuprofen
- Hydrocodone bitartrate
- Colloidal silicon dioxide
- A disintegrant
- A filler (cellulose-based)
- Starch
- A lubricant
- A low/bounded binder (alkylhydroxy methylcellulose)
The claims are built around three technical pillars:
1) Wet granulation of the drug/excipient blend into granules.
2) Blend uniformity and tablet performance despite formulation changes, including being able to compress over a range of compression forces without substantial change in disintegration time.
3) A structural/physical state requirement that ibuprofen, hydrocodone bitartrate, and lubricant (and in some claims granules + extra-granular material) are present in a single phase.
How broad is the independent claim set (Claims 1, 34-36)?
Your excerpt contains multiple independent or near-independent claims (1, 34, 35, 36). The differences mainly track whether the lubricant is explicitly recited in the single-phase requirement and whether the single-phase concept is applied to “granules + extra-granular material” vs “ibuprofen/hydrocodone/lubricant.”
Claim 1: single-phase requirement tied to drugs and lubricant
Claim 1 requires a tablet prepared by:
- (a) Wet granulation to form granules with ibuprofen, hydrocodone bitartrate, colloidal silicon dioxide, a disintegrant, a filler, and starch.
- (b) Blend granules with extra-granular material that contains a lubricant and at least one excipient.
- The formulation is substantially free of lactose and polyvinylpyrrolidone.
- The blend has:
- good flow,
- good compression performance,
- compressible over a wide range of compression forces with no substantial change in disintegration time.
- (c) Compress into a tablet where ibuprofen, hydrocodone bitartrate, and the lubricant are present in a single phase.
This is the most specific single-phase coupling: it forces a segregation/association constraint involving both actives and the lubricant.
Claim 34: single-phase framed as “granules + extra-granular material” without explicit drug-in-single-phase
Claim 34 is similar but expresses the single-phase requirement as:
- “granules and extragranular material are present in said tablet in a single phase.”
It is slightly less chemically descriptive about which individual ingredients occupy the single phase (though the ingredients are still functionally defined by what goes into granules vs extra-granular).
Claim 35: single-phase requirement again tied to drugs and lubricant, but extra-granular is more specific
Claim 35 is closer to Claim 1 but emphasizes:
- extra-granular material is comprised of lubricant and at least one excipient
- the tablet has ibuprofen, hydrocodone bitartrate, and lubricant present in a single phase.
Claim 36: a looser method definition plus single-phase granules vs extra-granular
Claim 36 requires:
- wet granulation with ibuprofen, hydrocodone, filler and starch (less explicit about colloidal silicon dioxide, disintegrant in the excerpt’s method step)
- blending with extra-granular material
- single phase in terms of granules and extragranular material.
Practical implication for infringement/validity analysis
- The claim language that locks “single phase” to specific constituents (actives + lubricant) narrows design-around space.
- The versions that describe single phase at the granule/extragranule level can still be asserted broadly, but they create more factual interpretation risk around what “single phase” means in the accused tablet.
What formulations are explicitly constrained (Claims 2-33)?
Claims 2-33 add numeric ranges for key components and define the binder composition. These ranges are not merely dependent “fallbacks”; they also provide strong evidence of which formulation levers the patentee treated as critical to the mechanical/disintegration behavior.
Claim 2: full numeric recipe backbone (with binder identity and lactose/PVP absence)
Claim 2 adds:
- Ibuprofen: ~25% to ~63% w/w
- Hydrocodone bitartrate: ~0.6% to ~3.8% w/w
- Colloidal silicon dioxide: ~0.5% to ~3% w/w
- Filler (microcrystalline cellulose or powdered cellulose): ~10% to ~42% w/w
- Disintegrant (croscarmellose sodium, crospovidone, sodium starch glycolate): ~4% to ~10% w/w
- Starch: ~11% to ~20% w/w
- Lubricant: <1% w/w
- Binder: ~2% to <6% w/w
- binder comprises alkylhydroxy methylcellulose
- It also defines the granule/extragranule composition in aggregate:
- granulate material comprises:
1) ibuprofen
2) hydrocodone
3) ~0.5% to ~2.0% colloidal silicon dioxide
4) ~9.5% to ~22% filler
5) ~4% disintegrant
6) ~6% to ~12% starch
- extra-granule material comprises remaining tablet material
- Still requires:
- substantial absence of lactose and polyvinylpyrrolidone
- flow, compression performance, and compression-force tolerance without substantial disintegration-time change.
Claims 3-17: narrowed filler/disintegrant/silicon dioxide/binder ranges
These dependents carve tighter ranges:
| Dependent claim |
Parameter |
Range (w/w of total tablet) |
| Claim 3 |
Filler |
~15% to ~25% |
| Claim 4/5 |
Disintegrant |
~6% to ~8% |
| Claim 6/7/8/9 |
Colloidal silicon dioxide |
~1.5% to ~2% |
| Claim 10-17 |
Binder (alkylhydroxy methylcellulose) |
~3% to ~4% |
Claims 4/5, 6-9, and 10-17 are largely the same range added under different dependency paths.
Claims 18-33: starch range narrowed to 6%–8%
A long chain of dependents constrains starch:
| Dependent claim(s) |
Parameter |
Range (w/w of total tablet) |
| Claims 18-33 |
Starch |
~6% to ~8% |
Note that Claim 2 initially states starch ~11% to ~20%. The later dependents (18-33) pull starch down to ~6% to ~8%. That means the patent family’s claim set covers multiple formulation strategies where starch level is a material variable for the mechanical and disintegration targets, but is not fixed.
What is the “single phase” limitation doing?
Across Claims 1, 34-36, “single phase” is the highest-interpretation constraint. It appears intended to control the spatial distribution of actives/lubricant (or granules vs extragranular components) such that tablet structure yields stable disintegration across compression-force windows.
How it differs by claim
- Claim 1 / 35: single phase explicitly includes:
- ibuprofen
- hydrocodone bitartrate
- lubricant
- Claim 34 / 36: single phase refers to:
- “granules and extragranular material” being present in a single phase
What it likely excludes (design-around intent)
- Two-phase segregated systems where:
- lubricant primarily resides in a distinct region,
- actives segregate differently in granules vs intergranular/extragranular space,
- compression induces microstructural separation that changes water ingress/disintegration behavior.
Because the claims also demand:
- “substantially free of lactose and polyvinylpyrrolidone,” and
- stable disintegration time over wide compression force,
“single phase” is likely tied to overcoming typical tableting sensitivity caused by phase separation or differential granule integrity.
What does the lactose/PVP exclusion constrain?
Across the excerpts:
- The composition is substantially free of lactose and polyvinylpyrrolidone.
This is both:
- a formulation constraint (excipient selection),
- and a narrowing device for composition-by-structure arguments if lactose or PVP were common in prior ibuprofen/opioid tablet approaches.
Tablet-making method scope: wet granulation and granule/extragranular architecture
The method scope is not limited to a generic mixing step. It specifies:
- wet granulation (granulating step comprises wet granulation)
- formation of granules using:
- ibuprofen + hydrocodone bitartrate
- colloidal silicon dioxide
- disintegrant
- filler
- starch
- blending with extra-granular material:
- includes lubricant and at least one excipient (in some versions)
- final compression into tablets with single-phase state.
This positions the patent against formulations that:
- use dry granulation,
- directly blend and compress without granulation,
- use different disintegrant classes not in the recited group (unless captured by literal claim terms via “a disintegrant” not restricted, but your excerpt shows disintegrant is later specified in dependents).
Patent landscape: where US 6,599,531 sits relative to product and process competitors
1) Composition vs method coverage
US 6,599,531 is anchored on combination product claims that recite:
- tablet composition architecture (granules vs extra-granular),
- and manufacturing method steps,
so it can be asserted even where accused infringers market the tablet rather than the process, depending on how courts treat method-limited product-by-process elements.
2) Likely competitive design-around axes (based on claim structure)
The strongest explicit “escape hatches” created by the language are:
- Remove the “substantially free of lactose and polyvinylpyrrolidone” feature by using lactose or PVP (though the “substantially free” standard depends on measurement and may not be easy to break cleanly).
- Change the excipient identities in the constrained groups:
- disintegrant not among croscarmellose sodium / crospovidone / sodium starch glycolate,
- filler not microcrystalline cellulose / powdered cellulose,
- binder not alkylhydroxy methylcellulose.
- Change granulation architecture (for claims that recite specific constituents in the wet granulation granules).
- Alter the tablet microstructure so “single phase” is not met, especially for Claims 1 and 35 where actives and lubricant must be in a single phase.
3) Litigation posture relevance of “compression-force tolerance”
The claims include functional performance language:
- “can be compressed over a wide range of compression forces with no substantial change in the disintegration time.”
That performance element can matter both for:
- infringement proof (what happens in the accused tablet under compression force variation),
- and validity (if prior art achieved similar performance without the same formulation architecture).
Claim chart style extraction: what must be true for Claim 1 (minimum checklist)
For a freedom-to-operate or infringement screen against an accused ibuprofen + hydrocodone bitartrate tablet, Claim 1 requires all of:
- Tablet composition includes:
- ibuprofen
- hydrocodone bitartrate
- colloidal silicon dioxide
- a disintegrant
- a filler
- starch
- a lubricant
- Manufacturing uses wet granulation to form granules from:
- ibuprofen + hydrocodone bitartrate + colloidal silicon dioxide + disintegrant + filler + starch
- Post-granulation blending combines granules with extra-granular material containing:
- lubricant and at least one excipient
- Composition is substantially free of lactose and polyvinylpyrrolidone
- Blend properties:
- flows well,
- good compression performance,
- compression over a wide range does not substantially change disintegration time
- Tablet internal state:
- ibuprofen, hydrocodone bitartrate, and lubricant are present in a single phase
This is the claim’s operative breadth: broad in actives, constrained in excipient types/categories, manufacturing method, and single-phase structural premise.
What the dependent claims add for narrower coverage (numeric windows)
If an accused product falls within:
- ibuprofen 25-63% and hydrocodone bitartrate 0.6-3.8%, and
- filler, disintegrant, silicon dioxide, starch and binder meet the specified windows,
then it aligns more closely with the dependent claim ladder.
The tightest dependent windows in your excerpt are:
- colloidal silicon dioxide ~1.5% to ~2%,
- binder ~3% to ~4%,
- starch ~6% to ~8%,
- disintegrant ~6% to ~8%,
- filler ~15% to ~25% (one dependent path).
Key Takeaways
- US 6,599,531 claims ibuprofen + hydrocodone bitartrate tablets made via wet granulation with a defined granule/extragranular architecture.
- The claim set hinges on a “single phase” structural limitation, with the narrowest versions requiring that ibuprofen, hydrocodone bitartrate, and lubricant all reside in a single phase.
- The composition is constrained by substantial absence of lactose and polyvinylpyrrolidone and by excipient identity families (cellulose filler; specified disintegrants; binder must be alkylhydroxy methylcellulose in the dependent ranges you provided).
- Dependent claims materially narrow coverage using numeric ranges for major components, with standout tight windows for colloidal silicon dioxide (~1.5% to 2%), binder (~3% to 4%), and starch (~6% to 8%).
- From a landscape view, the patent’s enforceability leverage is the combination of process architecture (wet granulation + extragranular blending) plus performance language (stable disintegration across compression forces) plus single-phase microstructure.
FAQs
1) What is the most limiting element in US 6,599,531?
The “single phase” limitation, especially in Claims 1 and 35 requiring ibuprofen, hydrocodone bitartrate, and lubricant to be present in a single phase.
2) Does the patent cover tablets made with dry granulation?
Not as written in the excerpt. The independent claims require wet granulation in the granulating step.
3) Can a competitor use lactose or PVP to avoid the claim?
The claims require “substantially free of lactose and polyvinylpyrrolidone,” so introducing lactose or PVP in an amount that defeats that limitation is a direct path to non-literal compliance, depending on how “substantially” is assessed.
4) Which excipients are explicitly constrained in the dependent claims?
The excerpt specifies: filler is microcrystalline or powdered cellulose, disintegrant is one of croscarmellose sodium/crospovidone/sodium starch glycolate, and binder is alkylhydroxy methylcellulose.
5) What ranges look most like “tight coverage” zones?
From the dependent chain: colloidal silicon dioxide (~1.5% to 2%), binder (~3% to 4%), disintegrant (~6% to 8%), filler (~15% to 25%), and starch (~6% to 8%).
References
[1] User-provided claim text for US Patent 6,599,531 (Claims 1-36 excerpt).
