US Patent 5,837,284: Scope, Claims, and Methylphenidate Patent Landscape
US Patent 5,837,284 claims oral, multipart methylphenidate dosage forms that generate two time-separated drug exposures: an immediate pulse and a delayed second pulse produced by coating with ammonio methacrylate copolymer(s). The claims define the dosage-form architecture (two particle groups), the drug loading and coating composition ranges, and multiple quantitative parameters tied to polymer composition and release timing.
What is the core inventive scope of US 5,837,284?
The claim set is built around one technological axis:
-
Two-component exposure design
- First particle group: provides a substantially immediate dose upon ingestion.
- Second particle group: uses coated particles to delay release 2 to 7 hours after ingestion (or administration).
-
Coating polymer identity
- Coating comprises pharmaceutically acceptable ammonio methacrylate (AM) copolymers.
-
Polymer quantitative identity that controls dissolution and timing
- Claims define AM copolymers by acrylic groups and quaternary ammonium groups ratio (10:1 to 50:1; dependent ranges narrower).
- Additional dependent claims define specific polymerized-unit ratios using TAMCl (trimethylammonioethyl methacrylate, commonly abbreviated as TAMCl in these formulations) with methacrylate and ethyl acrylate.
-
Quantitative drug loading and filler contents
- Second particle group drug loading: 2% to 75% by weight in admixture with binders (claim 1).
- Dependent claims narrow drug salt identity (dl-threo methylphenidate hydrochloride; d-threo methylphenidate hydrochloride).
- Dependent claims specify filler selection and content (e.g., talc at defined copolymer basis percentages).
-
Functional performance hooks
- Several claims shift from composition to release and pharmacokinetic profiles:
- in vitro release as two pulses temporally separated by 2 to 7 hours (claim 28).
- in vivo plasma profile as two maxima separated by 2 to 7 hours with peak magnitude difference constrained to ≤ 30% (claim 29).
Summary map of claim coverage (by claim type)
| Claim cluster |
What it locks down |
Key ranges / constraints |
| Architecture (multipart immediate + delayed) |
Two particle groups; delayed group is coated with AM copolymer |
Delay 2 to 7 hours |
| Salt specification |
dl-threo HCl and/or d-threo HCl |
Claims cover both stereoisomer salts across dependents and separate independent-style claim language (claims 27+) |
| Second-group formulation |
Coated particles drug loading + binders + AM copolymer coating |
Drug in second group 2% to 75% (claim 1); coating amount sufficient for delay window |
| Coating polymer chemistry |
AM copolymer quaternary ammonium-to-acrylic ratio |
10:1 to 50:1, then narrower (claim 13+) |
| Two-AM-copolymer blend |
Two AM copolymers with distinct TAMCl ratios in the coat |
Ratio ranges and blend ratio first:second copolymer (claims 17-20) |
| Filler |
Filler selection and talc content |
Talc selected (claims 8-12) with talc 35% to 45%, narrowing to 40% |
| Functional pharmacology |
Two pulses and two plasma maxima |
2-7 hours separation; plasma maxima difference ≤ 30% (claims 28-29) |
| Polymer ratio specificity |
Specific copolymerized-unit ratios using ethyl acrylate, methyl methacrylate, TAMCl |
Claim 30 gives explicit 2:1:0.1 and 2:1:0.2 examples |
What do the independent claim(s) actually claim?
US 5,837,284 includes multiple independent claim structures that cover similar concepts with different claim-language emphasis.
Claim 1 (multipart particle dosage form; immediate + delayed by AM copolymer coating)
Claim 1 is the broadest “architecture + polymer + timing” combination:
- Dosage form for oral administration of methylphenidate
- Two groups of particles, each containing methylphenidate drug
- First group: provides a substantially immediate dose on ingestion
- Second group: coated particles
- drug content in admixture with binders: 2% to 75% by weight of drug (in second group)
- coating: pharmaceutically acceptable ammonio methacrylate
- coating amount sufficient to provide delayed dose of 2 to 7 hours post-ingestion
Key claim-scoping levers in claim 1
- “substantially immediate dose” for the first group (scope depends on definition in spec, but the claim language is timing-functional)
- “coated particles” in the second group
- coating polymer identity fixed to ammonio methacrylate
- delay window fixed: 2 to 7 hours
- second-group drug loading: 2% to 75%
Claim 23 (once-daily form; immediate dose layer on exterior of delayed coating)
Claim 23 recasts the same concept into a once-daily product geometry:
- Once-daily oral administration dosage form
- (a) particles comprising 2% to 99% by weight methylphenidate in admixture with binders
- (b) an exterior coating comprising AM copolymer in amount sufficient to delay 2 to 7 hours
- (c) on the exterior surface of coating: a layer comprising methylphenidate drug to provide substantially immediate dose upon administration
Key scope distinction vs claim 1
- Claim 23 creates immediate delivery by a drug layer on the surface of the delayed coating, rather than a separate first particle group.
- Claim 23 allows higher drug loading in core particles: up to 99%.
Claim 27 (d-threo-methylphenidate hydrochloride, two groups)
Claim 27 is the parallel stereoisomer-focused multipart claim:
- Two groups of particles containing d-threo methylphenidate hydrochloride
- First group: substantially immediate upon ingestion
- Second group: coated particles with drug content 2% to 75% by weight in admixture with binders
- Coating: AM copolymer sufficient for delayed dose 2 to 7 hours
Claims 28-29 (functional performance: in vitro two pulses; in vivo two maxima)
These are narrower, performance-anchored claims that reduce design-around flexibility by describing release and plasma outcomes.
- Claim 28: “two pulses of drug release” in vitro separated by 2 to 7 hours
- Claim 29: in vivo plasma concentration with “two maxima” separated by 2 to 7 hours and maxima magnitude difference ≤ 30%
Claim 30 (explicit copolymer blend ratios using methyl methacrylate, ethyl acrylate, TAMCl)
Claim 30 gives explicit two-copolymer composition examples:
- first copolymer: methyl methacrylate, ethyl acrylate, TAMCl in ratio 2:1:0.1
- second copolymer: methyl methacrylate, ethyl acrylate, TAMCl in ratio 2:1:0.2
This is not a separate system; it is a limitation on the AM copolymer blend composition.
What is the detailed claim scope, parameter-by-parameter?
1) Immediate dose construction
US 5,837,284 claims two immediate delivery constructions:
- Immediate particle group (claim 1; claim 27)
- Exterior immediate drug layer on top of delayed coating (claim 23; also consistent with the “two exposure” concept)
Immediate particles are tied to methylphenidate salt powder formulations in dependent claims (claim 2; claim 4-6; claim 24-25).
2) Delayed pulse construction
Delayed pulse is tied to:
- a coating comprising pharmaceutically acceptable ammonio methacrylate
- delayed time window: 2 to 7 hours
- second-group drug loading in admixture with binders: 2% to 75% (claim 1; claim 27)
3) Methylphenidate salts covered
The claim set explicitly covers:
- dl-threo methylphenidate hydrochloride (claims 5-6)
- d-threo methylphenidate hydrochloride (claims 24-25, 27)
4) Drug loading ranges that matter for design-around
Key ranges:
- Second group drug: 2% to 75% by weight (claim 1; claim 27)
- Claim 23 core particle drug: 2% to 99% by weight (claim 23)
- Immediate first group: defined more by “substantially immediate” plus salt identity and first-group particle salt content range:
- first group salt amount: 2% to 99% by weight (claim 4)
The overlap between claim 1 and claim 23 means design-around must address both:
- the two-group/mixed immediate-delayed logic, and
- the AM coating polymer identity and timing window.
5) Coating polymer composition and ratio controls
Dependent claims specify the AM copolymer structural ratio:
- acrylic groups : quaternary ammonium groups = 10:1 to 50:1 (claim 13)
- narrower windows:
- 15:1 to 45:1 (claim 14)
- 15:1 to 20:1 (claim 15)
- 30:1 to 40:1 (claim 16)
These provide multiple “hooks” for infringement analysis because many candidate AM polymers could match the polymer class but not the specific quaternary-to-acrylic ratio.
6) Two-AM-copolymer blend architecture (coating blend)
Claims 17-20 require a coating comprising two different ammonio methacrylate copolymers, differentiated by their polymerized-unit composition:
- First copolymer: acrylic groups and trimethylammonioethyl methacrylate ratio 30:1 to 40:1 (claim 17)
- Second copolymer: acrylic groups and trimethylammonioethyl methacrylate ratio 15:1 to 20:1 (claim 17)
- blend ratio first copolymer : second copolymer:
- 90:10 to 99:1 (claim 18)
- 93:7 to 97:3 (claim 19)
- about 95:5 (claim 20)
This is highly specific chemistry coverage. If a product uses only one AM copolymer, or uses two AM copolymers with different TAMCl ratio bands, it can fall outside these dependent claims even if it stays within the broad AM class of claim 1.
7) Filler and talc content
A defined filler selection exists in claims 7-12:
- filler can be: talc, colloidal silica, fumed silica, gypsum, glycerine monostearate (claim 8)
- talc-specific nested claims:
- talc 35% to 45% by weight based on total weight of the copolymer (claim 10)
- talc 38% to 42% (claim 11)
- talc about 40% (claim 12)
Note the basis language: “based on the total weight of the copolymer.” This ties filler composition to polymer weight, which matters for analytical comparisons.
How does this claim scope map onto the competitive landscape?
The claims define a combination that is hard to replicate without touching multiple limitations simultaneously:
- oral methylphenidate
- two time-separated pulses (immediate + 2 to 7 hour delay)
- ammonio methacrylate coating
- specific polymer structural ratios or explicit two-copolymer blend compositions (in dependent claims)
- stereospecific salt coverage in dependents (d-threo and dl-threo)
Design-around pressure points
From a landscape perspective, the highest-risk areas for competitors are:
- any AM-coated methylphenidate product designed for a second exposure 2 to 7 hours after administration
- any product that uses two AM copolymers meeting the TAMCl-to-acrylic ratio bands and blend ratio windows of claims 17-20
- any product whose release or plasma profile is intentionally engineered to show two peaks with separation and amplitude difference constraints (claims 28-29)
The most common ways to avoid these claims would have to simultaneously move off:
- the AM copolymer identity (replace with different pH-responsive polymer system), and/or
- the two-pulse timing window, and/or
- the salt form coverage, and/or
- the immediate dose construction (separate first group vs surface drug layer), and/or
- the specific polymer composition ratios and blend constraints.
Litigation and freedom-to-operate implications (claim-focused)
US 5,837,284’s structure creates two different infringement pathways:
- Structural pathway: two group design + AM copolymer coating + drug loading + delay window (claims 1, 27, 23)
- Functional pathway: in vitro two pulses and in vivo two maxima profiles (claims 28-29)
Because of claim 28 and 29, an accused product cannot avoid risk merely by arguing about internal architecture if the measured release/plasma endpoints match the claim-described profiles.
Patent landscape view: where competitors likely cluster
Given the claim language, the landscape segmentation is:
-
AM-based biphasic methylphenidate oral dosage forms
- direct overlap with claims 1/23/27 via ammonio methacrylate and 2 to 7 hour delay windows
-
AM copolymer chemistry refinements
- products matching the AM copolymer structural ratios (claims 13-16, 17-20, 30) face narrower dependent-claim risk but potentially broader independent-claim risk if they still satisfy claim 1/23/27
-
Pulse timing optimization claims (2 maxima / 2 pulses)
- products whose marketed pharmacokinetic shape has two peaks separated by 2 to 7 hours and peak amplitude difference ≤ 30% fall into claims 28-29 design territory
-
Filler and processing-based variants
- talc and filler claims (7-12) can narrow infringement exposure but are often less central if other limitations are met
Claim-by-claim “scope inventory” (for infringement mapping)
| Claim |
Core limitation(s) |
What an examiner or FTO team checks |
| 1 |
two groups; first immediate; second coated with AM; second drug loading 2-75%; delay 2-7h |
core geometry; coating polymer identity; drug loading; timing |
| 2 |
first group is pharmaceutically acceptable salt powder |
first-group salt form and particle nature |
| 3 |
second group coated particles with pharmaceutically acceptable salt |
salt presence in coated core |
| 4 |
first-group salt amount 2-99% by weight |
quantitative salt loading in first group |
| 5-6 |
salt = dl-threo methylphenidate HCl |
stereoisomer identity |
| 7-12 |
filler selection and talc content |
excipient composition tied to copolymer basis |
| 13-16 |
acrylic/quaternary ammonium ratio bands |
exact AM copolymer structure ratios |
| 17-20 |
two AM copolymer blend with TAMCl ratios and blend ratio |
whether coating uses two distinct AMs with matchable ratios |
| 21-22 |
delay 3-6h or 4-5h |
whether designed delay lies in narrower windows |
| 23 |
once-daily; delayed AM coating + surface drug layer for immediate dose |
product architecture: surface layer vs particle group |
| 24-25 |
methylphenidate = dl-threo or d-threo HCl |
stereoisomer identity for this claim line |
| 26 |
coating uses two specific AM copolymer ratios (acrylic/TAMCl) |
chemical match to two-copolymer structure |
| 27 |
d-threo HCl version of two-group architecture |
stereoisomer-specific structural claim |
| 28 |
two in vitro release pulses separated 2-7h |
dissolution test endpoints and separation window |
| 29 |
two in vivo plasma maxima separated 2-7h; amplitude difference ≤30% |
PK peak shape and magnitude difference |
| 30 |
explicit copolymer ratio examples 2:1:0.1 and 2:1:0.2 |
exact polymerization unit ratio match |
Key Takeaways
- US 5,837,284 claims oral methylphenidate dosage forms with two exposure events: an immediate dose and a delayed dose 2 to 7 hours later, using ammonio methacrylate as the coating polymer.
- Independent claim coverage is split between (i) two particle groups (claims 1, 27) and (ii) once-daily cores with delayed AM coating plus a drug layer on the coating surface for immediate release (claim 23).
- Dependent claims lock in precise polymer chemistry bands (acrylic to quaternary ammonium ratios; and two-copolymer blends with defined TAMCl ratio windows and blend ratios).
- Functional claims (28-29) can capture products through in vitro two-pulse and in vivo two-maximum performance outcomes aligned to the 2 to 7 hour separation and ≤ 30% peak magnitude difference constraint.
FAQs
1) Does the patent require two separate particle groups in all embodiments?
No. Claim 23 uses a once-daily architecture with delayed AM coating and a methylphenidate layer on the exterior surface to produce the immediate dose.
2) What timing window is repeatedly claimed for the delayed component?
The delayed dose is claimed as 2 to 7 hours following ingestion (claims 1, 23, 27) and used similarly in the performance claims for pulses/maxima separation (claims 28-29).
3) Is ammonio methacrylate mandatory for infringement of the broad claims?
Yes. The coating in the core claim architecture is required to comprise a pharmaceutically acceptable ammonio methacrylate copolymer (claims 1, 23, 27).
4) Do the claims cover both d-threo and dl-threo methylphenidate hydrochloride?
Yes. The claim set explicitly references dl-threo methylphenidate hydrochloride (claims 5-6, 24) and d-threo methylphenidate hydrochloride (claims 24-25, 27, 28-29).
5) Can two-pulse performance alone be used to evaluate risk?
Yes. Claims 28-29 are performance-defined: they require two in vitro release pulses and two in vivo plasma maxima separated by 2 to 7 hours, with a peak magnitude difference limit in vivo.
References
[1] US Patent 5,837,284. Claims text as provided by user.
