How to Make Pill Coatings That Keep Medicine Stable Over Time
A method for coating pills with a specific plasticized acrylic polymer that ensures the medicine releases at a steady, predictable rate, even after sitting on a shelf for months.
Original patent title: “Controlled release formulations coated with aqueous dispersions of acrylic polymers”
A method for coating pills with a specific plasticized acrylic polymer that ensures the medicine releases at a steady, predictable rate, even after sitting on a shelf for months. Granted to Euro Celtique SA in 1997 with 15 claims and 1,092 forward citations.
Key facts
Coverage
What does this patent actually cover?
This patent describes a way to coat medicine-filled substrates, like beads or tablets, with a special acrylic polymer dispersion. The core mechanism involves curing the coated pill at a temperature above the polymer's glass transition temperature for 24 to 60 hours. This process stabilizes the coating, ensuring that the rate at which the medicine dissolves in the body remains consistent even after the pill has been stored in hot and humid conditions. By achieving this stability, the manufacturer guarantees that the drug release profile does not shift by more than 15% after a month of accelerated storage.
The gap
What does this patent NOT cover?
- Does not cover coatings made from polymers other than ammonio-methacrylate copolymers.
- Does not cover formulations that are not cured at a temperature above the polymer's glass transition temperature.
- Does not cover coatings that do not include a permeability-enhancing agent or pore-former.
- Does not cover immediate-release medications that do not require a controlled release profile.
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
What made this novel
The innovation is the specific curing process—heating the coated pill above its glass transition temperature for a long duration—which forces the polymer particles to fuse into a stable, uniform film that resists environmental degradation.
Schematic visualization of the patent's claim structure. Hand-drawn diagrams in progress for each landmark patent.
Where you've seen this
Real-world examples
OxyContin extended-release tablets
Various 12-hour and 24-hour controlled-release opioid medications
Extended-release analgesic beads in capsules
Why it matters
The bigger picture
This technology was essential for the commercial success of long-acting opioid analgesics, such as OxyContin. By ensuring that the drug release rate remained stable during storage, manufacturers could reliably market pills intended to provide pain relief over 12 or 24 hours. The patent became a cornerstone of the pharmaceutical industry's ability to produce consistent, extended-release oral dosage forms.
Filed
June 2, 1995
Granted
June 17, 1997
Market context
Who's building on this
Companies in this space
The technology was primarily developed and utilized by Purdue Pharma and its affiliates. Today, major generic pharmaceutical manufacturers continue to use similar polymer-coating techniques to develop bioequivalent versions of controlled-release medications.
Market impact
This patent enabled the mass production of reliable, long-acting pain management drugs, which transformed the treatment of chronic pain. It created a high barrier to entry for competitors by establishing a specific, validated manufacturing process for stable controlled-release coatings that became an industry standard.
Claim 1 — Plain English
What this patent covers
This patent describes a way to coat medicine-filled substrates, like beads or tablets, with a special acrylic polymer dispersion. The core mechanism involves curing the coated pill at a temperature above the polymer's glass transition temperature for 24 to 60 hours. This process stabilizes the coating, ensuring that the rate at which the medicine dissolves in the body remains consistent even after the pill has been stored in hot and humid conditions. By achieving this stability, the manufacturer guarantees that the drug release profile does not shift by more than 15% after a month of accelerated storage.
The clever bit
The innovation is the specific curing process—heating the coated pill above its glass transition temperature for a long duration—which forces the polymer particles to fuse into a stable, uniform film that resists environmental degradation.
What it does not cover
- Does not cover coatings made from polymers other than ammonio-methacrylate copolymers.
- Does not cover formulations that are not cured at a temperature above the polymer's glass transition temperature.
- Does not cover coatings that do not include a permeability-enhancing agent or pore-former.
- Does not cover immediate-release medications that do not require a controlled release profile.
Patent timeline
Application submitted to the patent office
Application published, typically 18 months after filing
Patent officially issued
PatentBrief Score
Impact Score
Moderate
Citation count
40/40
Highly cited
Claim breadth
10/20
Broad claimsclaimsThe numbered statements at the end of a patent that legally define what the inventor owns.Read more →
Recency
0/20
Older than 20 years
Assignee scale
0/20
Independent or smaller assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →
PatentBrief Impact Score — based on citation count, claim breadth, recency, and assignee scale. Not a legal assessment.
Heuristic Value Estimate
What this patent might be worth
$169K – $540K
Midpoint $338K · expired or expiring · industry ×3.0
Heuristic only — blends forward/backward citation counts, claim scope, time remaining, litigation history, and CPC-derived industry baseline. Real valuations need a professional appraisal.
The original legal language
Original claims
15 claims as filed with the patent office.
Concepts involved
Citations
Patent lineage
Cite this patent
Jr., F. P., Oshlack, B., & Chasin, M. (1997). How to Make Pill Coatings That Keep Medicine Stable Over Time (U.S. Patent No. 5,639,476). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/5639476/nicoderm-nicotine-patch
Auto-generated from the patent record. Double-check author order and the issue date against the official USPTO document before submitting.
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Common Questions
Frequently Asked Questions
What does How to Make Pill Coatings That Keep Medicine Stable Over Time cover?
A method for coating pills with a specific plasticized acrylic polymer that ensures the medicine releases at a steady, predictable rate, even after sitting on a shelf for months.
Who owns patent US 5639476?
Euro Celtique SA owns this patent, granted in 1997.
When does this patent expire?
This patent has expired and is now in the public domain — anyone can use the invention freely.
What is patent US 5639476 cited by?
This patent has been cited by 1092 later patents that build on its ideas.
What problem does this patent solve?
This technology was essential for the commercial success of long-acting opioid analgesics, such as OxyContin. By ensuring that the drug release rate remained stable during storage, manufacturers could reliably market pills intended to provide pain relief over 12 or 24 hours. The patent became a cornerstone of the pharmaceutical industry's ability to produce consistent, extended-release oral dosage forms.
What does this patent NOT cover?
Does not cover coatings made from polymers other than ammonio-methacrylate copolymers.
Patent monitoring