Executive summary
US Patent 6,228,398 claims a multiparticulate oral modified-release formulation that produces pulsatile in vivo delivery from two or more populations of drug-loaded particles, where each subsequent population includes a modified-release coating and/or modified-release matrix engineered to delay release. The claim set is broad at the framework level (multi-population, same or different active ingredient, coating or matrix, pulsatile release) and narrows in dependents toward ADHD-use methylphenidate and toward specific dissolution timing windows and specific polymer coating chemistries (methacrylate/ammonio methacrylate copolymers). In practice, this creates a core licensing and freedom-to-operate (FTO) risk zone for pulsatile multiparticulate methylphenidate and for alternative platforms that meet the “first population releases first, subsequent population releases later via modified coating/matrix” structure, even if the final product is branded differently.
What patents protect multiparticulate pulsatile modified-release methylphenidate in the US (US 6,228,398 scope)?
Direct claim thesis of US 6,228,398
The independent claim (claim 1) is structured as a platform:
- Multiparticulate modified release composition for oral delivery
- Contains at least one active ingredient
- Has a first component comprising a first population of active-ingredient-containing particles
- Has at least one subsequent component comprising a subsequent population of active-ingredient-containing particles
- The active ingredient(s) in first and subsequent components are the same or different
- At least one subsequent population further comprises either:
- a modified release coating, or
- a modified release matrix material (or both)
- After oral delivery, the composition delivers the active ingredient(s) in a pulsatile manner.
Key platform levers (what must be present to infringe)
- Multiparticulate particle populations: at least two populations with different release roles (first vs subsequent).
- Modified-release mechanism is tied to the “subsequent” populations via coating or matrix.
- Pulsatile in vivo delivery is the functional outcome.
- Active ingredient may be general, but methylphenidate is explicitly covered.
What parts of the claim are broad versus limiting?
- Broad: same/different actives across populations; coating vs matrix; immediate vs modified release is optional in the independent but becomes typical in dependents; inclusion in solid dosage forms is claimed broadly (capsules; minitablets; multilayer tablets; rapidly dissolving dosage form).
- Limiting:
- specific embodiments: two populations only (claim 2), immediate then modified (claim 3/15), in vitro dissolution windows (claim 19/20 and claim 28), in vivo mimicking immediate-release dosing schedules (claim 17/18), and pH-dependent polymer systems with methacrylate copolymers (claims 33–36).
How many claims in US 6,228,398 cover coatings versus matrix-based pulsatile release?
Claim-level breakdown (from your claim text)
- Claim 1: subsequent populations may have modified release coating OR modified release matrix material (or both).
- Claims 4 and 5 narrow that embodiment:
- Claim 4: modified release component comprises particles with modified release coating
- Claim 5: modified release component comprises modified release matrix material
Practical implication
Both common design routes are covered:
- delayed/triggered coat-controlled systems (including pH-dependent copolymers), and
- delayed matrix-controlled systems.
So an FTO review cannot screen only coating-based platforms; matrix-based multiparticulate pulsatile systems can read on the independent claim structure if they maintain the “first population then subsequent delayed pulse(s)” delivery logic.
When does US 6,228,398 lose enforceability for generic entry risk in the US?
No enforceability timetable can be produced from the information provided. You provided the claim set but not filing date, priority date, patent grant date, maintenance fee status, terminal disclaimer information, or any PTA/TSA adjustments. Without those, it would be inaccurate to compute a USPTO/term end date or to map a generic entry risk window.
What is the claim scope for methylphenidate specifically in US 6,228,398?
Direct methylphenidate coverage
- Claim 13: active ingredient comprises methylphenidate or pharmaceutically acceptable salts, or optically pure or racemic mixtures.
- Claim 18 and claim 37 reinforce methylphenidate/enantiomer/salt coverage in dependent contexts.
Treatment indication framing
- Claim 29/31/32/30: methods of treatment for attention deficit disorder (ADD/ADHD) via administering the claimed composition.
- Claim 30: method tied to build up of patient tolerance (a functional condition statement).
In vivo performance hooks tied to methylphenidate
- Claim 17/18: in vivo release mimics administration of two or more doses of immediate release forms.
- Claim 19/20: specific dissolution releases (in aqueous medium), which can act as a proxy for expected biological pulsing for methylphenidate embodiments.
What are the key dissolution and timing limitations that narrow infringement?
These dependents create measurable “guardrails” that can become noninfringement arguments if a competitor product deviates.
In vitro release window (claims 19–20)
- Claim 19 (for first vs subsequent populations):
- First population: ~50–100% released within 4 hours
- Subsequent population: ~25–55% released between 4 and 8 hours
- Claim 20 tightens:
- First population: ~80–100% within 4 hours
- Subsequent population: ~28–55% between 4 and 8 hours
Total dissolution profile (claim 28)
A different embodiment uses total active ingredient release timing:
- ~50% released within ~30 minutes
- ~4% released between ~30 minutes and 4 hours
- ~28% released between 4 and 8 hours
Implication for design-around
A competitor with a different pulse shape, different trigger delay, or different dissolution partition between populations may try to avoid reading on dependents even if it reads on the independent concept. However, because claim 1 is functional (“pulsatile manner”), complete avoidance can be harder than it appears if the in vivo effect still matches a pulse delivery pattern.
What pH-dependent polymer coating limitations exist (and how tight are they)?
Core pH-dependent pulse claims
- Claim 33: pH dependent polymer coating releases a pulse following a delay time
- Claim 34: coating comprises methacrylate copolymers
- Claim 35: coating is a mixture of methacrylate and ammonio methacrylate copolymers with a ratio sufficient to achieve pulse after delay
- Claim 36: explicitly sets methacrylate : ammonio methacrylate copolymers = 1:1
How tight these are
- Claims 33–35 are moderately narrowing by polymer class and functional “pulse after delay.”
- Claim 36 is the tightest: an explicit 1:1 ratio. A product using materially different ratios may still read on claim 33/35 but can attempt to avoid claim 36.
How does US 6,228,398 treat “immediate plus delayed pulse” multiparticulates?
Two complementary dependent structures appear in your text:
-
Immediate-first, modified-subsequent
- Claim 3: first component is immediate release, subsequent component is modified release
- Claim 15: restates first immediate then subsequent modified
- Claim 16: requires substantially all active from first population releases before release from subsequent population.
-
Immediate-release dosing mimicry
- Claim 17/18: in vivo release mimics the same active given as two or more immediate-release doses.
Practical interpretation for infringement
If a product has a clear initial drug “burst” from one population, followed by later pulse(s) from coated or matrix-delayed particles, the product aligns tightly with these dependent embodiments, and any deviation must be framed around the population separation and the timing sequence.
What solid oral dosage form variations are covered (capsules, multilayer tablets, mini-tablets)?
US 6,228,398 extends beyond the particle blend into multiple oral dosage formats:
- Claim 21: solid oral dosage form comprising the multiparticulate modified release composition
- Claim 22: blend of particles filled into hard or soft gelatin capsules
- Claim 23: particles separately compressed into mini-tablets then filled into hard/soft gelatin capsules
- Claim 24: particles in multilayer tablets where first vs subsequent components are in different layers
- Claim 25: incorporated in a rapidly dissolving dosage form
- Claim 26: rapidly dissolving dosage form is a fast-melt tablet.
Implication
Even if a company adopts a non-capsule format, the patent’s “composition to dosage form” dependency can preserve infringement risk if the underlying particle population structure and pulsing mechanism remain intact.
How does US 6,228,398 compare with other common “pulsatile delivery” ADHD platforms?
Competitive separation by mechanism (using only the claim architecture you provided)
Many ADHD extended-release candidates rely on one of these archetypes:
- osmotic or monolithic matrices with continuous release,
- single-component diffusion/erodible systems,
- single coated pellet/mini-tablet with one main delay.
US 6,228,398 differentiates by requiring:
- two or more distinct populations (first and subsequent), and
- modified coating/matrix only (or at least) on the subsequent population to generate a pulse outcome.
So the strongest match is a product designed to create a distinct “second stage” pulse after an initial stage. Single-stage continuous-release products are more likely to avoid the “pulsatile” functional requirement, but the boundary depends on the exact in vivo release profile.
What patent litigation or Orange Book listing status affects enforcement risk for US 6,228,398?
No Orange Book listings, litigation documents, or settlement records are provided in your input. Without that, it would be inaccurate to attribute any current Paragraph IV posture, generic attempt, or carve-out to US 6,228,398.
How strong is the patent estate for pulsatile multiparticulate delivery under US 6,228,398’s claim structure?
Strength indicators from the claims themselves
- Breadth at the independent level: two-stage multiparticulate, coating or matrix, same/different active ingredient, pulsatile functional outcome.
- Multiple fallback positions: coating route (claims 4/33–36) and matrix route (claim 5), plus dosage form fallbacks (capsules, multilayer tablets, fast-melt).
- Measured performance dependents: dissolution timing windows (claims 19/20, 28) can strengthen validity arguments by showing objective performance characteristics.
Main vulnerability points
- Functional claim limitation: “pulsatile manner” can trigger disputes about what level of pulsing is required.
- Dependents with specific numeric windows: these can be used to argue noninfringement if the competitor’s dissolution and timing differ.
Key design-around themes implied by the claim set
- Use one population (eliminate “first population” vs “subsequent population” structure).
- Shift the modified-release mechanism to the first population rather than the subsequent.
- Avoid pH-dependent methacrylate/ammonio methacrylate copolymer coating ratios if the product depends on that embodiment.
- Alter pulse timing/dissolution partitioning so it does not satisfy numeric dependents (claims 19/20/28).
- Change dosage form alone does not necessarily help, because multiple oral dosage forms are claimed as dependent structures.
Key Takeaways
- US 6,228,398 claims a multiparticulate, two-stage (or multi-stage) oral system that delivers drug in a pulsatile pattern, with modified release coating and/or matrix on subsequent particle populations.
- The patent is broad on the formulation architecture (first vs subsequent particle populations; same/different actives; coating vs matrix).
- It is narrower in dependents through measurable dissolution timing windows and through pH-dependent methacrylate/ammonio methacrylate copolymer coatings (including a specific 1:1 ratio in claim 36).
- It covers multiple solid oral formats (capsules, mini-tablet blends, multilayer tablets, fast-melt tablets) provided the particle-population and pulsing structure is maintained.
- Methylphenidate and ADHD treatment methods are explicitly within the claim set, creating direct relevance to common ADHD extended-release design patterns.
FAQs
1) Does US 6,228,398 require the first component to be immediate release?
No. Claim 1 only requires a first population and at least one subsequent population with modified release coating/matrix on the subsequent population(s). The immediate-release limitation appears in dependent claims (notably claims 3 and 15).
2) Can the same active ingredient be used in both first and subsequent populations?
Yes. Claim 1 explicitly allows the active ingredient in the first and subsequent components to be the same or different.
3) Are both coating-based and matrix-based designs protected?
Yes. Claim 1 covers modified release coating and/or modified release matrix material; dependent claims 4 and 5 isolate those embodiments.
4) What is the most specific polymer embodiment in the claim set?
Claim 36 specifies a methacrylate : ammonio methacrylate copolymer ratio of 1:1.
5) Do capsule vs tablet formats change infringement exposure?
They can affect how the product is assembled, but the patent includes multiple dosage forms as dependent claims. Format alone is unlikely to avoid infringement if the underlying multiparticulate pulsing structure is used.
References
No sources were provided or cited beyond the claim text supplied in the prompt.
