United States Patent 5,232,705 Landscape: Osmotic, Expandable-Wall Dosage Forms for Twice-Daily Verapamil and Other Actives

US Patent 5,232,705 covers an osmotic dosage form with an expandable composition that swells when exposed to entering fluid to drive drug release, plus a drug-free interval (for twice-daily or sequential dosing) generated by a drug-free composition inside a fluid-permeable wall, with instantaneous/“substantially immediate release” drug on the external wall surface in at least one independent claim. The estate is tightly framed around expandable push systems and permeable-wall osmotic delivery, with claim breadth driven by (i) device architecture elements and (ii) lists of actives and salts, including verapamil as the principal example.

What patents protect US 5,232,705 scope (osmotic expandable dosage forms with drug-free interval)?

What is claimed at the architectural level?

Across independent claims (and claim 2), the patent requires a combination of structural and functional elements:

Core device architecture

Compartment with a wall that “surrounds and forms” the compartment.
Wall is permeable to passage of fluid.
Exit means in the wall for communication between exterior and compartment (claim 1 allows general exit means; claim 5 specifies “pore”).
A third composition that expands upon fluid entry, increasing dimensions and pushing drug constituents toward release.

Release-control via internal compartment stratification

First composition: drug-free in claim 1 (or “substantially drug-free” in claim 2) to create a drug-free interval prior to drug administration.
Second composition: drug-containing composition for therapeutic effect.

External surface immediate release (claim 1)

Claim 1 adds a substantially immediate release dose amount of drug on the exterior surface of the wall, linked to twice-daily dosing from a single dosage form.

Two-dose variant (claim 2)

Claim 2 removes the external “immediate release” requirement as drafted, and instead places a first dose of drug “for producing a therapeutic effect on the exterior surface of the wall,” then uses the internal drug-free interval and second dose for sequential delivery.

Which actives are included in the claim set?

Claim 3 and claim 4 provide two explicit active lists that can anchor scope and enforceability:

Calcium-channel blockers and related agents (claim 3)

verapamil, nimodipine, nitredipine, nisoldipine, nicardipine, felodipine, diltiazem, lidoflazine, tiapamil, guanabenz, isradipine, gallopamil, amlodipine, mioflazine, caroverene.

Nitro vasodilators and related nitrates (claim 4)

amyl nitrate, glyceryl trinitrate, octyl nitrite, sodium nitrite, erythrityl tetranitrate, isosorbide dinitrate, mannitol hexanitrate, pentaerythritol tetranitrate, pentritol, triethanolamine trinitrate, trolnitrate phosphate.

What formulations are explicitly defined for verapamil?

Claim 6 is an architecture plus numeric and material constraints:

verapamil in a range of 25 nanograms to 1.5 grams.
“third composition” that expands on fluid entry to physically increase dimensions and push.
exit means for delivery.

Claim 7 is a “therapeutic composition” claim:

verapamil amount 0.05 ng to 1.5 g
plus a polymer selected from:
- poly(vinyl pyrrolidone)
- poly(alkylene oxide)
- poly(cellulose)
and it states utility for antianginal, antiarrhythmic, and antihypertensive effects.

Claim 8 adds that verapamil can be a pharmaceutically acceptable salt.

How broad are the claims: what elements are likely limiting?

Claim 1 and claim 2 are limited by “multiple-compartment functional layering”

The enforceable scope is not just “osmotic dosage form.” The claims require a specific functional sequence:

drug-free (or substantially drug-free) internal composition creating a drug-free interval, paired with
an expandable composition that is activated by fluid ingress and drives push,
plus an exit means in a fluid-permeable wall.

This combination is structurally and functionally tight. A competitor omitting the drug-free interval element or omitting the expandable push element materially reduces risk.

“Substantially immediate release” on an exterior surface is a major differentiator (claim 1)

Claim 1 requires:

“substantially immediate release dose amount of drug on the exterior surface of the wall.”

If a product keeps all drug within an internal compartment and does not place an immediate-release dose externally on the wall, claim 1 is less likely to be captured as written.

The polymer list in claim 7 constrains “therapeutic composition” scope

Claim 7 restricts “therapeutic composition” to:

verapamil with specific polymer classes (PVP, poly(alkylene oxide), poly(cellulose)).

A generic formulation outside these polymer classes would reduce direct literal coverage of claim 7, though it could still face coverage under device-architecture claims (claim 1/2/6) depending on actual structure.

Which parts of the patent drive enforceability: device claims vs “therapeutic composition” claims?

Device claims (1, 2, 5, 6) are strongest for blocking competing oral dosage forms

Because device claims recite:

wall permeability,
expandable third composition,
exit means,
drug-free interval,
and (for some claims) exterior immediate-dose design,

they are the most likely to interfere with competing oral osmotic push technologies that attempt to replicate a once-daily-to-twice-daily clinical profile using osmotic systems.

Therapeutic composition claims (7, 8) can matter in ingredient-focused enforcement

Claim 7 and 8 are useful for:

licensing deals involving specific verapamil/polymer combinations in an osmotic system,
and for asserting infringement when a competitor uses those polymer classes with verapamil amounts within the recited ranges.

What formulations are protected by US 5,232,705?

Verapamil osmotic, expandable push delivery

Protected formulation concepts:

verapamil-containing second composition (and potentially exterior dose on the wall),
expandable composition that swells on fluid ingress to push drug out through wall exit means,
polymer-containing “therapeutic composition” option (claim 7) using PVP, poly(alkylene oxide), or poly(cellulose).

Other enumerated actives

If a competitor uses the same osmotic device architecture with a listed drug from claim 3 or 4, the scope can extend beyond verapamil. The lists also support arguments against “design-around by selecting a different drug within the list.”

Salts

Claim 8 explicitly includes pharmaceutically acceptable salts of verapamil, expanding literal coverage to salt forms.

When does US 5,232,705 lose exclusivity?

US 5,232,705 is a U.S. utility patent; the standard term is generally 20 years from the earliest effective non-provisional filing date plus any adjustments. Exclusivity beyond patent term (e.g., pediatric exclusivity) cannot be inferred from the provided claim text alone.

Because the earliest filing date and any PTA/PTE are not provided here, the exclusivity end date cannot be stated precisely.

How many patents cover this technology: related patent families and likely overlapping claims?

No patent family members, continuation(s), divisional(s), or related continuations are provided in the prompt. Without the specification bibliographic data (application number, priority date, assignee, and other family members), a complete landscape with counts, expiration distribution, and overlapping claim charts cannot be produced from the information given.

What generic entry risks exist for verapamil twice-daily osmotic products?

Highest literal infringement risk scenarios

A generic or follow-on product is most exposed if it includes all of the following:

an osmotic, fluid-permeable wall forming a compartment,
a drug-free (or substantially drug-free) internal composition creating a drug-free interval,
a third expandable composition that swells on fluid ingress and physically pushes drug toward release,
exit means in the wall (pore or other pore-like exit).

If the formulation is also engineered to place a substantially immediate-release verapamil dose externally on the wall surface for twice-daily delivery (claim 1), risk increases.

Lower-risk design-around patterns

Products that change one of the required pillars can reduce literal infringement:

eliminate the internal drug-free interval element,
remove or materially alter the expandable push composition mechanism,
move away from a fluid-permeable wall + exit means construct,
avoid an external immediate-release wall dose for products targeting claim 1 specifically.

How strong is the patent estate for this kind of osmotic push system?

Strength can only be assessed from claim construction and the number of independently relevant claim sets. From the claim text alone:

The estate appears to have a device-centric core (claims 1, 2, 5, 6) and a formulation-centric secondary layer (claims 7, 8).
The explicit inclusion of expandable composition activated by fluid ingress is the central technical anchor.
The external immediate-dose requirement narrows claim 1’s device coverage.

Without the prosecution history, claim amendments, dependent claim count beyond those provided, and the full claim set, a credible litigation-grade strength rating cannot be derived.

What patent litigation affects US 5,232,705?

No litigation docket numbers, parties, or settlements are provided. Without that information, no case-specific impact can be stated.

What is the Orange Book status of US 5,232,705?

Orange Book listing status is product-specific (NDA/ANDA), and it requires drug name and approval IDs. The prompt includes actives but not the relevant NDA/ANDA tied to this patent’s Orange Book record. A complete Orange Book status cannot be produced from the provided inputs.

Commercial exposure: what products most likely map to this claim set?

Given the prominent inclusion of verapamil in claims 6-8 and the active list breadth, the most relevant commercial exposure is tied to:

verapamil osmotic or push-pull dosage forms marketed for antianginal or hypertension indications, especially those designed for twice-daily or staged release using a drug-free interval.

But mapping requires the actual marketed products and their dosage-form schematics, which are not provided.

Key claim-by-claim scope map (what must exist to infringe?)

Claim	Required infringement elements (as drafted)	Main risk driver
1	Single dosage form for twice-daily; compartment + fluid-permeable wall; first drug-free composition for drug-free interval; second drug composition; third expandable composition; exit means in wall; substantially immediate-release drug on exterior wall surface	External immediate-dose + drug-free interval + expandable push + osmotic wall
2	Dosage form for first dose and second dose; compartment + fluid-permeable wall; first dose on exterior wall; first substantially drug-free internal composition for drug-free interval; second drug composition; expandable third composition; exit means	Two-stage dosing with exterior first dose and internal second dose
3	Claim 2 device with drug in listed group (CCBs, etc.)	Active selection within list
4	Claim 2 device with drug in nitro/nitrate list	Active selection within list
5	Claim 2 device where exit means is a pore	Mechanical exit design detail
6	Wall + first delaying composition; verapamil amount 25 ng to 1.5 g; expandable third composition pushing first/second; exit means delivering verapamil	Numeric verapamil range + “means for delaying” + expandable push
7	Therapeutic composition: 0.05 ng to 1.5 g verapamil + polymer selected from PVP, poly(alkylene oxide), poly(cellulose); deliverable from osmotic dosage form; stated therapeutic uses	Specific formulation ingredient classes and ranges
8	Claim 7 where verapamil is a pharmaceutically acceptable salt	Salt form

Key Takeaways

The patent’s enforceable scope is dominated by a specific osmotic device mechanism: a fluid-permeable wall, an expandable third composition triggered by fluid ingress, and exit means for drug delivery.
A core differentiator is the drug-free interval generated by an internal drug-free/substantially drug-free composition (claims 1 and 2).
Claim 1 uniquely requires a substantially immediate-release drug dose on the exterior surface of the wall, which narrows literal coverage versus devices where all drug is internal.
Verapamil coverage is reinforced by formulation-anchored dependent claims, including verapamil quantity ranges and polymer class limitations (claims 6-8).
A full U.S. landscape, expiration schedule, Orange Book status, and litigation impact cannot be completed from the claim text provided.

FAQs

What design changes most reliably avoid claim 1’s “exterior surface substantially immediate-release” limitation?
Does claim 2 cover devices that do not have an internal “drug-free interval” layer?
Which drug substitutions are explicitly covered for claim 2 based on the enumerated active lists in claims 3 and 4?
Are verapamil salts covered under the “therapeutic composition” claims, and how does that affect generic formulation strategy?
What exit means structures are sufficient under claim 5’s “pore” limitation compared with non-pore exit geometries?

References

United States Patent 5,232,705. (Claims provided in prompt).

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	108999	⤷ Start Trial
Australia	648822	⤷ Start Trial
Australia	8500091	⤷ Start Trial
Canada	2088376	⤷ Start Trial
Germany	69103153	⤷ Start Trial
Denmark	0546038	⤷ Start Trial
European Patent Office	0546038	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 5,232,705

Summary for Patent: 5,232,705