US Patent 4,777,049: Scope, Claim Construction, Expiration, and Osmotic Drug-Delivery Patent Landscape

US Patent 4,777,049 covers osmotic drug-delivery systems that combine a semipermeable wall, an internal beneficial agent, a modulating agent, and a delivery passageway to produce a release profile combining pulsed delivery with substantially zero-order delivery. The patent is directed to delivery architecture and release kinetics, not to a particular drug product alone. It issued on October 11, 1988, and its original 17-year term expired on October 11, 2005, assuming no unusual term adjustment or extension. It therefore does not create current US exclusivity.

The most commercially important limitations are the required modulating agent, the pulsed-release function, and the osmotic device structure. Conventional osmotic systems that provide only continuous zero-order delivery, or systems lacking the claimed modulator, generally fall outside the asserted scope.

What technology does US Patent 4,777,049 protect?

US Patent 4,777,049, titled “Osmotic System with Pulsed Delivery,” protects osmotic systems designed to generate a controlled release interrupted or followed by a pulse. The core mechanism is a semipermeable membrane that permits environmental fluid to enter while retaining the beneficial agent and, in relevant claims, the modulating agent.

The patent requires four functional elements:

Element	Claimed requirement
Semipermeable wall	Permeable to exterior fluid
Retention function	Substantially impermeable to beneficial or useful agent
Internal compartment	Contains beneficial agent and modulating agent
Delivery outlet	Passageway connects the compartment to the external environment
Release behavior	Modulating agent produces pulsed delivery, often combined with zero-order release

The invention relies on changes in the concentration and solubility of the modulating agent inside the device. As water or another external fluid enters through the membrane, the modulator can initially maintain a particular solubility environment. As its concentration falls, the solubility of the drug can increase, producing a pulse.

The patent therefore combines structural limitations with release-profile limitations. Both categories matter in infringement analysis.

How many independent claims does US Patent 4,777,049 contain?

The supplied claims contain four principal independent claim groups:

Claim 1: An osmotic system containing a beneficial agent and modulating agent.
Claim 11: A process for delivering a useful agent at a zero-order rate modulated by pulses.
Claim 13: An osmotic system using a therapeutically acceptable salt with a common ion.
Claim 14: A process producing constant and pulsed release within the same release period.

Claims 10 and 13 are drafted as dependent claims referring back to claim 1, although each adds substantial drug-specific or formulation-specific limitations.

Claim hierarchy

Claim	Type	Principal limitation
1	Apparatus/system	General osmotic system with a pulsed-delivery modulator
2	Dependent	Modulator below saturation, followed by zero-order delivery
3	Dependent	Modulator enhances beneficial-agent solubility
4	Dependent	Modulator concentration decreases and produces a later pulse
5	Dependent	Pulse delivers a larger amount than zero-order delivery
6	Dependent	Cellulosic wall and solubility-ratio formula
7	Dependent	Modulator is acid, base, or salt
8	Dependent	Beneficial agent is a drug
9	Dependent	Environment of use is an animal
10	Dependent	Salbutamol-specific device
11	Independent process	Osmotic delivery at zero-order rate modulated by pulses
12	Dependent process	Modulator falls below saturation, increasing useful-agent solubility
13	Dependent system	Therapeutically acceptable common-ion salt
14	Independent process	Constant and pulsed release during the same release period

What does claim 1 require?

Claim 1 is the broadest system claim. A potentially infringing system must contain:

A semipermeable wall;
A compartment enclosed by that wall;
A beneficial agent in the compartment;
A modulating agent in the compartment;
A passageway through the wall;
A modulator that provides pulsed delivery.

The claim does not require salbutamol, a particular dosage form, a specific membrane polymer, a defined pulse interval, or a particular modulating compound.

The claim does require a functional relationship between the modulating agent and the pulse. Merely placing an excipient, buffer, salt, acid, or base in an osmotic tablet would not necessarily satisfy the claim. The accused component must perform the claimed modulation function.

Structural scope

The wall must be semipermeable. It must allow external fluid to enter while substantially preventing passage of the beneficial agent. The claim does not expressly require the wall to be impermeable to the modulating agent, although later claims and the process claims impose more specific retention requirements.

The passageway can be formed by drilling, laser ablation, mechanical formation, or another method, provided it connects the external environment with the internal compartment and permits delivery of the agent.

Functional scope

Claim 1 uses “pulsed delivery” as a central limitation. The patent specification would be important in determining whether a particular release curve qualifies as a pulse. A small fluctuation in release rate may not be enough. The claimed pulse is tied to the modulator’s effect on internal solubility and delivery.

How do claims 2 through 5 narrow the patent scope?

Claims 2 through 5 describe different release mechanisms and quantitative relationships.

Claim 2: Below-saturation modulation

Claim 2 requires the modulating agent to be present below the amount needed to maintain saturation in incoming fluid. The drug’s release begins with a pulse and then changes to substantially zero-order delivery.

This claim is narrower than claim 1 because it requires a specific concentration condition and a specific sequence:

Initial pulsed delivery;
Subsequent substantially zero-order delivery.

Claim 3: Solubility enhancement

Claim 3 requires the beneficial agent’s solubility to increase in the imbibed fluid in the presence of the modulator. The pulse interrupts a substantially zero-order release pattern.

This claim is directed to a pulse caused by a solubility-enhancing interaction rather than merely a concentration decline.

Claim 4: Declining modulator concentration

Claim 4 requires the modulator concentration to decrease in the incoming fluid and produce a pulse after a substantially zero-order period. The sequence is the reverse of claim 2:

Substantially zero-order release;
Later pulsed release.

Claim 5: Pulse-volume relationship

Claim 5 requires the pulsed amount of beneficial agent to be larger than the amount delivered at the substantially zero-order rate. This is a quantitative limitation. A device with a pulse that is merely detectable, but not larger than the relevant zero-order delivery amount, may not satisfy this claim.

What formulations are protected by claim 6?

Claim 6 adds two limitations:

The wall contains a cellulose ester, cellulose diester, cellulose triester, cellulose ether, or cellulose ester-ether.
The ratio of modulating agent to useful agent falls within the formula:

[ 0 < R < \frac{S_o}{S_d} ]

where:

(R) is the amount ratio of modulating agent to useful agent;
(S_o) is the mutual solubility of the modulating agent;
(S_d) is the mutual solubility of the useful agent.

This is a formulation-specific claim. It is narrower than claim 1 because a noncellulosic membrane, or a formulation outside the stated ratio, would not meet claim 6 even if it met the broader system limitations.

The formula creates several potential claim-construction issues:

The patent must define how mutual solubility is measured.
The relevant solvent or fluid must be identified.
The ratio must be evaluated under the conditions relevant to the osmotic device.
The meaning of “useful agent” must be read consistently with “beneficial agent.”

A generic osmotic tablet using cellulose acetate as its membrane may still fall outside claim 6 if the modulator-to-drug ratio does not satisfy the formula.

What modulating agents are covered?

Claim 7 identifies four broad categories:

Inorganic acids;
Organic acids;
Bases;
Salts.

The claim is not limited to a named modulator. It could cover a broad range of pharmaceutically acceptable or technically suitable compounds, subject to the requirements of claim 1.

Claim 13 is narrower. It requires a therapeutically acceptable salt having a common ion with the beneficial agent. The common-ion relationship is important because it can influence the solubility equilibrium of the active ingredient.

For example, a beneficial agent and modulating salt may share a cation or anion. The claim does not cover every salt used in an osmotic formulation. The common-ion limitation must be present, and the salt must be therapeutically acceptable.

What does claim 10 cover for salbutamol?

Claim 10 is directed to an osmotic device for controlled delivery of salbutamol. In the United States, salbutamol is generally referred to as albuterol.

The claim requires:

A nontoxic semipermeable wall;
A wall substantially impermeable to salbutamol and the modulating agent;
A compartment containing salbutamol and a modulating agent;
The modulator to be present below the amount required to maintain saturation;
An increase in the amount of salbutamol in solution as fluid enters;
A pulsed release of salbutamol;
A passageway for controlled delivery.

Claim 10 is materially narrower than claim 1 because it is drug-specific and requires a particular unsaturated-modulator mechanism. It would not ordinarily cover every sustained-release salbutamol formulation. A salbutamol inhaler, conventional matrix tablet, depot injection, or nonosmotic oral formulation would not satisfy the required device structure.

The claim also does not by itself establish FDA approval, an Orange Book listing, or market exclusivity for salbutamol. Patent rights and FDA regulatory rights are separate systems. The FDA Orange Book principally lists patents submitted for approved drug products under the applicable Hatch-Waxman framework, not every historical drug-delivery patent. [2]

How do process claims 11, 12, and 14 differ from the system claims?

Claims 11, 12, and 14 protect use or operation of the osmotic system rather than only the physical device.

Claim 11 requires:

Placing the device in an environment of use;
Imbibing fluid through the semipermeable wall;
Delivering the useful agent through the passageway;
Producing zero-order delivery modulated by a pulse.

Claim 12 narrows claim 11 by requiring the modulator concentration to fall below saturation and increase the solubility of the useful agent.

Claim 14 requires a release pattern containing both:

A constant release rate; and
A pulsed release rate during the same release period.

The process claims could present different infringement questions from the system claims. A device manufacturer may avoid a system claim but still face a process argument if the product is used in the claimed manner. Conversely, a process claim requires proof that the relevant release pattern occurs during operation.

What is the patent expiration date?

Event	Date or status
Patent	US 4,777,049
Issue date	October 11, 1988
Original term for pre-June 8, 1995 application	17 years from issue
Expected expiration	October 11, 2005
Current enforceability	Expired
Current generic-entry blocking power	None from this patent alone

US patent law changed from a 17-year-from-issue term to a 20-year-from-effective-filing-date term for qualifying applications filed on or after June 8, 1995. [3] US 4,777,049 is an older patent and therefore falls under the earlier term framework, subject to any applicable terminal disclaimer, reissue, or patent-term extension.

No patent-term extension under 35 U.S.C. § 156 would ordinarily be expected for a 1988 drug-delivery patent unless the patent was tied to an eligible approved product and statutory requirements were satisfied. [4] The patent’s subject matter also does not create present exclusivity after expiration.

What is the Orange Book status of US Patent 4,777,049?

US 4,777,049 should not be treated as a currently effective Orange Book patent. It is a device and formulation patent issued decades ago, and its term expired in 2005.

The patent does not independently establish:

FDA approval of salbutamol or albuterol;
A listed drug product;
New chemical entity exclusivity;
Three-year clinical-investigation exclusivity;
Pediatric exclusivity;
A current Hatch-Waxman litigation bar.

A Paragraph IV certification can be commercially relevant only against an unexpired listed patent. Because US 4,777,049 has expired, it cannot independently support a current Paragraph IV exclusion period or block an ANDA launch. The Hatch-Waxman framework treats patent certification and regulatory exclusivity as distinct from the historical existence of a patent. [2, 5]

Which companies are challenging the patent?

There is no current US patent-challenge risk from US 4,777,049 because the patent expired in 2005. A modern ANDA applicant would not need to challenge this patent to obtain launch clearance.

Historical litigation, licensing, and settlement analysis must be separated from present freedom to operate. Even if the patent was asserted during its term, those historical events would not revive the patent or extend its enforceability.

The commercially relevant question is whether later patents claim:

Specific osmotic tablets;
Particular membrane compositions;
Albuterol or salbutamol formulations;
Layered osmotic systems;
Laser-drilled delivery orifices;
Manufacturing processes;
Drug-specific release profiles;
Combination products.

Those later rights would require a separate family and product-level search. US 4,777,049 alone does not establish current patent coverage.

How strong is the patent estate?

The patent estate created by US 4,777,049 is historically broad in concept but weak for current enforcement because the patent has expired.

Dimension	Assessment
Core technology	Broad osmotic delivery architecture
Drug specificity	Limited, except for dependent claim 10
Formulation specificity	Moderate in claims 6, 7, and 13
Release-profile limitation	Strong and central
Manufacturing coverage	Limited
Current enforceability	None
Current Orange Book risk	None from this patent alone
Biosimilar risk	Not applicable to a small-molecule delivery patent
Generic risk	No blocking risk from this expired patent
Know-how value	Potentially relevant if retained as trade secret, but not patent exclusivity

The most defensible historical claim scope would have involved products combining an osmotic membrane with a drug-plus-modulator compartment and a pulse-producing release mechanism. The weakest scope would have involved generic controlled-release products lacking the claimed modulator or pulsed pattern.

How does this patent compare with conventional osmotic delivery patents?

US 4,777,049 differs from conventional osmotic systems that aim only for a steady release rate.

Attribute	Conventional osmotic system	US 4,777,049
Primary objective	Continuous controlled release	Pulse superimposed on controlled release
Required modulator	Not necessarily	Yes
Release profile	Substantially steady	Pulsed, interrupted, or followed by zero-order release
Drug specificity	Usually broad	Broad, with salbutamol species claim
Membrane	Semipermeable	Semipermeable
Delivery orifice	Required in many systems	Required
Current patent value	Depends on later patents	Expired

The invention’s distinguishing feature is not osmosis alone. It is the use of a modulating agent to alter drug solubility and create a defined pulse within an osmotic delivery profile.

What generic launch risks exist?

US 4,777,049 creates no current generic-launch barrier. A generic manufacturer can launch a product that would have required a design-around or license during the patent term, subject to later patents and FDA requirements.

Historical design-around options would have included:

Removing the modulating agent;
Using a nonosmotic controlled-release mechanism;
Using a formulation that does not generate a pulse;
Selecting a different release profile;
Changing the internal solubility system;
Using a delivery architecture without the claimed passageway arrangement.

A present launch analysis must focus on unexpired continuation, divisional, improvement, formulation, or product patents. Patent expiration does not eliminate regulatory requirements, product-performance requirements, or infringement risks under later patents.

What are the key geographic and manufacturing considerations?

The patent is a US patent. Its enforceability was limited to the United States and its territories. Corresponding foreign family members, if any, would have had separate filing dates, claim scopes, maintenance obligations, and expiration dates.

The patent’s manufacturing barriers are relatively limited. It claims the device architecture and release behavior rather than a highly specific manufacturing process. A manufacturer could potentially reproduce the general concept using different:

Cellulose derivatives;
Membrane thicknesses;
Modulators;
Drug loads;
Passageway sizes;
Coating methods;
Manufacturing equipment.

The patent’s technical teaching may still have historical value for formulation development, but technical know-how is not equivalent to an enforceable patent right.

Key Takeaways

US 4,777,049 covers osmotic systems using a modulating agent to create pulsed delivery.
Claim 1 requires a semipermeable wall, internal beneficial agent, internal modulating agent, passageway, and pulsed-release function.
Claims 2 through 5 narrow the release sequence, solubility behavior, concentration change, and pulse magnitude.
Claim 6 adds cellulose-based membranes and a solubility-ratio formula.
Claim 10 is directed specifically to pulsed osmotic delivery of salbutamol.
Claims 11, 12, and 14 cover operation and release processes.
The patent issued on October 11, 1988, and its expected 17-year term expired on October 11, 2005.
It has no current standalone Paragraph IV, Orange Book, generic-launch, or biosimilar significance.
Current commercial risk would arise from later patents, not from US 4,777,049.
Biosimilar analysis is not applicable because salbutamol is a small molecule and this patent is not a biologic patent.

FAQs

Can an expired osmotic delivery patent still block an albuterol product?

No. An expired patent cannot support an injunction or current patent-based launch block. Later unexpired patents may still matter.

Does claim 10 cover all sustained-release salbutamol products?

No. Claim 10 requires a specific osmotic device with a semipermeable wall, internal modulator, sub-saturation condition, and pulsed salbutamol release.

Is a cellulose acetate membrane alone enough to infringe claim 6?

No. Claim 6 also requires the claimed beneficial-agent and modulator arrangement and the specified solubility-ratio relationship.

Could a formulation avoid the patent by using a continuous release profile?

During the patent term, a formulation that lacked the claimed pulsed delivery function could have had a noninfringement position. That issue is no longer material for US 4,777,049 because the patent has expired.

Does US 4,777,049 provide exclusivity for an FDA-approved albuterol product?

No. FDA approval, regulatory exclusivity, and patent protection are separate rights. This expired patent does not provide current product exclusivity.

References

United States Patent and Trademark Office. (1988). Osmotic system with pulsed delivery, U.S. Patent No. 4,777,049.
U.S. Food and Drug Administration. (2023). Approved drug products with therapeutic equivalence evaluations.
35 U.S.C. § 154. Patent term.
35 U.S.C. § 156. Extension of patent term.
21 U.S.C. § 355(j). Abbreviated applications for new drugs.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Canada	1251708	⤷ Start Trial
Germany	3443586	⤷ Start Trial
Spain	293000	⤷ Start Trial
Spain	295960	⤷ Start Trial
Spain	538104	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 4,777,049

Summary for Patent: 4,777,049