United States Patent 6,149,938: Scope, Claims, and Landscape for Mouth-Soluble, Rapidly Disintegrating Tablets
What does US 6,149,938 claim, and what is the core protected subject matter?
US 6,149,938 is directed to a process for making a specific type of granulate used to formulate mouth-soluble, rapidly disintegrating tablets. The claims focus on a fluidized-bed granulation with tightly defined ingredients and constraints, followed by drying in the same fluidized bed. A second set of claims then covers tablets made from that granulate and gives a disintegration time window.
Claim set overview
- Claims 1-5: Process claims defining the granulation recipe and parameters.
- Claims 6-7: Product claims covering tablets containing the claimed granulate and disintegration time.
- Claim 8: A method of making the tablet using the claimed granulate.
Structural claim logic
The patent’s claim scope is anchored on four technical pillars:
- Granulation in a fluidized bed
- A recipe containing:
- a polyalcohol
- an active ingredient
- 1 to 30% of an edible acid with an explicit restriction that it is not part of an acid-base effervescent mixture
- optionally, other solids (lubricant, sweetener, flavor)
- a polymer aqueous solution/dispersion that contributes 1 to 10% of final granulate weight
- Drying in the fluidized bed
- Product claims tied to mouth-soluble, rapidly disintegrating tablets made with the resulting granulate.
What exactly is the claim 1 scope (the “main gate”)?
Independent process claim (Claim 1)
Claim 1 requires all of the following elements:
(i) Granulating in a fluidized bed comprising:
- (a) a polyalcohol
- (b) an active ingredient
- (c) from 1 to 30% of an edible acid
- Constraint: the edible acid is not part of an effervescent mixture consisting of an acid and a base
- (d) optionally, other solid components
- lubricants, sweetening agents, and flavors (as a defined group)
- (e) an aqueous solution or dispersion of a water-soluble or water-dispersible polymer
- polymer is present such that it provides 1 to 10% of the final weight of the granulate
(ii) Drying the granulate in the fluidized bed
Key scope consequence
Because claim 1 is written as a single process sequence with defined inputs and a defined drying step, any accused process that:
- uses granulation but not in a fluidized bed,
- substitutes the polymer step outside the specified aqueous solution/dispersion construct or outside 1-10% final granulate contribution,
- uses an acid that is part of an acid-base effervescent system,
- or omits the fluid-bed drying step,
risks falling outside claim 1.
How do dependent claims narrow the ingredient universe?
Dependent claims narrow the claim 1 material lists.
Claim 2: Polymer class
Water-soluble or water-dispersible polymers are limited to one of:
- polyethylene glycols
- sodium carboxymethyl cellulose
- hydroxypropylmethyl cellulose
- xanthan gum
- polyethylene oxide
- polyoxyethylene
- polyoxypropylene Pluronic®
- acrylic and methacrylic acid polymers (Eudragit®)
- carrageenin
- polyvinyl alcohol
Practical effect: even if claim 1 would read on a broader polymer, claim 2 makes a narrower embodiment explicit. In enforcement terms, claim 2 supports narrower claim pathways tied to particular excipient families.
Claim 3: Polyalcohol class
Polyalcohols are limited to:
- mannitol, xylitol, sorbitol, erythritol, maltitol, lactitol
Claim 4: Further restriction
Polyalcohol selection limited to:
Claim 5: Active ingredient coating
In the claim 1 process, the active ingredients have been coated before granulation.
Practical effect: claim 5 adds a pre-processing step that can matter for both stability (taste masking, moisture protection) and particle engineering. If an accused process uses coated actives, it more readily maps to claim 5.
What do the tablet product claims cover (Claims 6-7)?
Claim 6
“Mouth-soluble, rapidly disintegrating tablets comprising the granulate of claim 1.”
This ties product coverage directly to the claimed granulate composition and process lineage. If a tablet is not made with a granulate that satisfies claim 1, claim 6 is not directly met.
Claim 7: Disintegration time metric
Tablets of claim 6 having:
- disintegration time from 30 seconds to 3 minutes
Practical effect: This metric is a key objective boundary. It converts “rapidly disintegrating” into a measurable window. If a formulation disintegrates outside this range, claim 7 is narrowed; claim 6 might still be asserted depending on how “rapidly disintegrating” is argued and measured in the case record.
How does Claim 8 expand protection to a tablet manufacturing method?
Claim 8
“A process of making a mouth-soluble, rapidly disintegrating tablet comprising comprising the granulate of claim 1 and optionally, other components to form a tablet.”
This is a downstream method claim. It does not re-specify tablet excipients beyond “optionally, other components” and does not restate disintegration time. Coverage therefore attaches if:
- the tablet-making process uses the claimed granulate, and
- the resulting product qualifies as mouth-soluble and rapidly disintegrating in the patent sense.
What is the functional and legal boundary created by the “no effervescent mixture” restriction?
Claim 1 includes a bright-line exclusion:
- the edible acid must not be part of an effervescent mixture consisting of an acid and a base.
This matters because many prior art fast-disintegrating tablets use acid-base pairs to generate carbon dioxide and accelerate wetting and breakup. US 6,149,938 narrows itself to non-effervescent acid use.
Landscape implication
- Technologies built on bicarbonate/citric acid or similar acid-base effervescence are structurally distinguishable on this element.
- Competitors using acid-base effervescence may design around by swapping to non-effervescent acids or by using effervescence outside the claimed “edible acid” construct (though claim interpretation can turn on how mixtures are characterized).
What is “polymer at 1-10% of final granulate weight” doing to the claim scope?
The polymer constraint is both quantitative and functional (water-soluble/dispersible polymer used in an aqueous solution/dispersion during granulation).
- polymer provides 1-10% of final granulate weight
- aqueous solution/dispersion is incorporated during fluid-bed granulation and then dried in the same process
Design-around lever
A competitor attempting to remain outside the claim can target:
- polymer level below 1% or above 10% (depending on process and accounting),
- switching to non-aqueous binder systems,
- or using polymers that are neither water-soluble nor water-dispersible (depending on claim interpretation).
What does the patent imply about intended formulation architecture?
Even though claim language is process-centric, the ingredient selection implies a particular tablet architecture:
- polyalcohol (e.g., mannitol/xylitol/sorbitol) as a bulk matrix and mouthfeel component,
- edible acid in 1-30% to drive fast wetting/disintegration without acid-base gas generation,
- polymer binder/dispersant as 1-10% to create granular integrity and control breakup,
- optionally lubricants/sweeteners/flavors,
- and potentially coated actives for stability or taste management.
How broad is the active ingredient coverage?
The claims are active-ingredient agnostic:
- Claim 1 includes “an active ingredient” without listing drug classes.
- Claim 5 references “active ingredients have been coated before granulation” without restricting the active.
Enforcement consequence
If an infringing granulate exists, the patent is positioned to cover many actives so long as the excipient system and process limitations are met. The scope is excipient/process-driven rather than API-driven.
Where does the patent sit in the mouth-dissolving / fast-disintegrating patent landscape?
US 6,149,938 is best categorized as a formulation-processing patent in the fast-disintegrating oral dosage space, specifically using:
- fluidized bed granulation,
- non-effervescent acid within a defined range,
- polymer aqueous binder/dispersant at a defined fraction,
- and polyalcohol matrices.
Within typical landscape groupings, it overlaps with:
- orally disintegrating tablet (ODT) technologies that rely on rapid wetting and breakup,
- taste masking and stability approaches using coated actives,
- granulation-based manufacturing patents (granulate-first then tableting).
What are the likely claim-proving evidence points for infringement?
For a plaintiff, the most direct evidentiary chain is:
- Reconstruct or test the accused process to confirm:
- fluidized bed granulation,
- inclusion of polyalcohol,
- inclusion of edible acid at 1-30%,
- edible acid not in acid-base effervescent mixture,
- aqueous polymer solution/dispersion present,
- polymer contributes 1-10% of final granulate weight,
- drying in fluidized bed.
- Confirm the granulate is used to make the tablet.
- Measure tablet disintegration time (for claim 7).
For a defense, the most direct counter-strategies are:
- dispute presence/composition of the edible acid (and whether any base exists to make it effervescent),
- dispute polymer type, solubility/dispersibility, and amount (1-10% granulate basis),
- dispute process steps (fluid bed granulation and/or drying),
- dispute disintegration timing window for claim 7.
What do the independent and dependent claims practically cover for competitors?
Competitive space most at risk
- Rapidly disintegrating tablets where granules are made via fluid bed with polyalcohol + non-effervescent edible acid + aqueous polymer binder at 1-10%, followed by fluid bed drying.
- Tablets where actives are coated before granulation and the coated actives are then granulated in the same system (claim 5 path).
- ODTs claiming a disintegration time aligned to 30 seconds to 3 minutes (claim 7 path).
Design-around zones
- Using an effervescent acid-base pair as a deliberate wetting mechanism can create a mismatch with the “not part of an effervescent mixture consisting of an acid and a base” requirement.
- Moving polymer binder function to:
- different polymer type (outside claim 2, but still potentially within claim 1 if water-soluble/dispersible),
- or outside the 1-10% granulate weight range,
- or outside aqueous solution/dispersion inclusion,
creates potential noninfringement.
- Eliminating fluid-bed drying or granulating outside a fluidized bed breaks a required step of claim 1.
- Achieving a disintegration profile outside 30 seconds to 3 minutes can reduce claim 7 exposure, though claim 6 can still remain.
Key Takeaways
- US 6,149,938 protects a fluidized-bed granulation and drying process that builds a granulate for mouth-soluble, rapidly disintegrating tablets using:
- polyalcohol,
- 1-30% edible acid with a non-effervescent limitation,
- aqueous solution/dispersion of water-soluble/dispersible polymer contributing 1-10% of granulate weight,
- optional lubricants/sweeteners/flavors,
- and drying in the fluidized bed.
- Tablet claims (claims 6-7) are granulate-dependent, and claim 7 adds a measurable 30 seconds to 3 minutes disintegration window.
- The “not part of an effervescent mixture” element is the primary structural constraint that differentiates this patent from acid-base effervescence fast-disintegration approaches.
- The landscape position is excipient and process-driven, so enforcement can extend across many APIs as long as the granulation architecture matches.
FAQs
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Is the patent limited to specific drugs or drug classes?
No. The claims cover “an active ingredient” without restricting the API.
-
What is the most critical limitation in claim 1 besides fluidized bed processing?
The edible acid must be 1-30% and not part of an acid-base effervescent mixture.
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Does claim 1 require the polymer to be one of the listed polymers in claim 2?
Claim 1 requires a water-soluble or water-dispersible polymer at 1-10% of granulate weight. Claim 2 further narrows the polymer list to specified examples.
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What does claim 7 protect specifically?
Tablets of claim 6 with a measured disintegration time of 30 seconds to 3 minutes.
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Can a tablet be covered by claim 6 even if it disintegrates slower than 3 minutes?
Claim 6 covers mouth-soluble, rapidly disintegrating tablets comprising the claim 1 granulate. Claim 7 is the specific disintegration-timing limitation.
References
[1] US Patent 6,149,938. “Process for making granulate for mouth-soluble rapidly disintegrating tablets” (claims as provided).
