US Patent 4,238,485: Scope, Claims, Expiration, and Patent Landscape for Timolol-Hydrochlorothiazide Combinations

US Patent 4,238,485 covers fixed-dose antihypertensive compositions combining a specified beta blocker with a 1,2,4-benzothiadiazine diuretic, principally the combination of timolol maleate and hydrochlorothiazide. The narrowest claims correspond to tablets containing the equivalent of 10 mg of the beta blocker and 25 mg of hydrochlorothiazide, the formulation associated with Merck's Timolide product.

The patent issued on December 9, 1980. Under the pre-Uruguay Round patent-term rule applicable to the patent, its ordinary 17-year term from grant would have ended on December 9, 1997, absent an earlier terminal disclaimer or other limiting event. It therefore does not present a current US patent barrier to generic manufacture or sale.

What does US Patent 4,238,485 cover?

The patent claims a pharmaceutical combination rather than the beta-blocker molecule itself. Its core subject matter is:

A beta-blocking agent within a defined chemical genus.
A thiazide-type diuretic.
A specified weight ratio between the two active ingredients.
Particular stereochemical and salt forms.
Tablet dosage strengths.
A method of treating hypertension using the composition.

The patent's central combination is a beta blocker structurally corresponding to timolol and hydrochlorothiazide.

Patent element	Scope
Therapeutic class	Antihypertensive combination
Beta blocker	Formula-defined morpholino or piperidino compound
Relevant commercial compound	Timolol, particularly the (-) isomer
Salt form	Hydrogen maleate, corresponding to timolol maleate
Diuretic	1,2,4-benzothiadiazine or pharmaceutically acceptable salt
Principal commercial diuretic	Hydrochlorothiazide
Broad ratio	Beta blocker:diuretic of approximately 1:1 to 1:10
Narrow ratio	Approximately 1:1.25 to 1:5
Claimed dosage forms	Tablets
Specific dosage	10 mg beta blocker and 25 mg diuretic
Indication	Reduction of blood pressure in hypertensive animals, including humans

The claims do not cover every beta blocker and every diuretic. They require the specific chemical genus and the claimed benzothiadiazine class.

Which drug does the claimed beta blocker identify?

The claim limitations point to timolol and related analogs.

Timolol is a beta-adrenergic receptor antagonist whose chemical structure contains the morpholino-substituted thiadiazole portion and the tert-butylamino side chain described in the claims. Claim 6 narrows the alkyl group to tert-butyl. Claim 7 narrows the active ingredient to the salt of the (-) isomer. Claim 8 identifies the hydrogen maleate salt.

The relevant progression is:

Claim	Chemical limitation
Claim 1	Broad formula-defined beta blocker; salts and mixtures
Claim 3	Isopropyl or tert-butyl substituent
Claim 4	Morpholino member
Claim 6	tert-Butyl member
Claim 7	Salt of the (-) isomer
Claim 8	Hydrogen maleate salt

Taken together, claims 6 through 8 describe timolol hydrogen maleate, commonly called timolol maleate. The claim language is broader than timolol alone until those dependent limitations are applied.

The patent does not claim the basic timolol molecule as a standalone active pharmaceutical ingredient. A party manufacturing timolol without combining it with the claimed thiazide formulation would not infringe the composition claims solely by making or selling timolol.

How broad is claim 1?

Claim 1 is the principal composition claim. It requires all of the following:

A beta-blocking agent from the specified formula.
A non-toxic pharmaceutically acceptable salt of that compound, or a mixture of the compound and salt.
A 1,2,4-benzothiadiazine or pharmaceutically acceptable salt.
A beta blocker-to-diuretic weight ratio of approximately 1:1 to 1:10.
Use as a composition for treating hypertension.

The claim is composition-based. It does not require a particular tablet coating, excipient, dissolution profile, manufacturing process, packaging configuration, or release profile.

The ratio limitation is material. A formulation outside the claimed ratio range would have a potential noninfringement position, subject to claim construction and the doctrine of equivalents. The term "about" creates flexibility around the numerical endpoints, but it does not eliminate the ratio requirement.

Claim 1 also covers:

The free beta-blocker compound.
A pharmaceutically acceptable salt.
Mixtures containing both the compound and salt.
A broad class of benzothiadiazine diuretics.
Salts of the diuretic.

A product containing timolol maleate and hydrochlorothiazide would fall within claim 1 if its active-ingredient ratio remains within the stated range.

What formulations are protected by claims 2 through 12?

Claims 2 through 12 progressively narrow the composition.

Claims 2 and 12: thiazide selection

Claim 2 identifies:

Chlorothiazide.
Alkali-metal salts of chlorothiazide.
Hydrochlorothiazide.

Claim 12 lists a much broader set of benzothiadiazines:

Flumethiazide.
Benzthiazide.
Cyclopenthiazide.
Cyclothiazide.
Trichloromethiazide.
Benzhydroflumethiazide.
Methylcyclothiazide.
Polythiazide.
Thiabutazide.
Hydrochlorothiazide.
Chlorothiazide.
Pharmaceutically acceptable salts of those compounds.

Claim 12 is unusual in that it returns to the broader beta-blocker scope of claim 1 while specifying a closed or substantially enumerated group of diuretics. A product using a listed diuretic other than hydrochlorothiazide may fall within claim 12 if the remaining claim 1 elements are satisfied.

Claims 3 through 6: beta-blocker narrowing

These claims narrow the beta blocker by substituent and ring system:

Claim 3: isopropyl or tert-butyl group.
Claim 4: morpholino substituent.
Claim 5: hydrochlorothiazide.
Claim 6: tert-butyl group.

The claim 6 combination is therefore the morpholino, tert-butyl beta blocker with hydrochlorothiazide. In commercial terms, this is the timolol-hydrochlorothiazide combination.

Claims 7 and 8: stereochemistry and salt

Claim 7 requires the salt of the (-) isomer. Claim 8 specifies the hydrogen maleate salt.

These limitations are important because they distinguish the claimed commercial active from:

The opposite enantiomer.
The racemate.
Other pharmaceutically acceptable salts.
The free base, unless the claim is read through an applicable salt or mixture limitation.
Other beta blockers in the broader genus.

Claims 9 through 11: ratio and tablet strength

Claim 9 narrows the ratio to approximately 1:1.25 through 1:5.

Claim 10 covers tablets containing:

5 or 10 mg of the beta blocker; and
10, 25, or 50 mg of the diuretic.

Claim 11 narrows the formulation to a tablet containing 10 mg of the beta blocker and 25 mg of hydrochlorothiazide.

Claim	Commercial relevance
8	Timolol hydrogen maleate plus a listed diuretic
9	Preferred active-ingredient ratio
10	Tablet dosage-strength group
11	10 mg/25 mg timolol-hydrochlorothiazide tablet

What does claim 13 cover?

Claim 13 is a method-of-treatment claim. It covers administering a blood-pressure-reducing amount of a composition falling within claim 1 to a hypertensive animal.

The claim has three principal limitations:

The administered composition must satisfy claim 1.
The subject must be a hypertensive animal.
The administered amount must reduce blood pressure.

The method claim does not independently protect use of timolol or hydrochlorothiazide as monotherapies. It requires the claimed combination. It also does not cover every use of the combination outside hypertension treatment.

For current US enforcement, claim 13 would face practical limits because the patent expired in 1997. During the patent term, method claims could have been relevant to commercial promotion or prescribing-related allegations, subject to the applicable infringement standard and statutory safe harbors.

When did US Patent 4,238,485 lose exclusivity?

The patent issued December 9, 1980. Its ordinary expiration date was December 9, 1997, based on the 17-year term from grant applicable to pre-June 8, 1995 US applications under 35 U.S.C. § 154 in its then-applicable form.

Event	Date
Patent issued	December 9, 1980
Ordinary 17-year expiration	December 9, 1997
Current status	Expired
Current blocking effect	None from this patent

The patent predates modern patent-term adjustment and patent-term extension regimes. There is no apparent basis for treating it as a currently enforceable patent right.

Patent expiration removes the exclusionary right but does not erase historical relevance. The patent remains important for:

Historical product development.
Prior-art analysis.
Freedom-to-operate reviews involving expired claims.
Generic product and formulation history.
Assessment of Timolide's original patent position.

What is the Orange Book status of US Patent 4,238,485?

US Patent 4,238,485 was associated with the fixed-dose timolol-hydrochlorothiazide product concept rather than with timolol as a standalone active ingredient.

The patent cannot currently provide enforceable Orange Book exclusivity because it expired in 1997. Any historical Orange Book listing would have no remaining blocking term. The relevant regulatory distinction is:

Regulatory issue	Effect
Patent listing	Historical relevance only after expiration
Current ANDA block	None based on this expired patent
Paragraph IV risk	No current litigation risk based solely on this patent
30-month stay	Not available for an expired patent
Market entry	Not blocked by US 4,238,485
Product-specific exclusivity	Must be assessed separately from patent term

The regulatory status of the underlying product and any active NDA must be analyzed separately from patent status. A discontinued or inactive branded product does not revive an expired patent, and an active NDA does not create perpetual formulation exclusivity.

Are there Paragraph IV challenges or patent litigation involving this patent?

Because US Patent 4,238,485 expired in 1997, a present-day Paragraph IV challenge to this patent would have no practical legal objective. An ANDA applicant could not trigger a meaningful 30-month stay based on an expired patent.

The relevant litigation assessment is therefore historical:

The patent could have supported an infringement action during its term.
Any Paragraph IV certification filed before expiration would have had to address the patent's validity, enforceability, and infringement.
After expiration, the patent cannot support a new injunction against generic entry.
Any historical litigation would require review of PACER, Federal Circuit opinions, district court dockets, FDA patent-listing records, and settlement documents.

The supplied claim set does not identify a particular litigation matter or settlement agreement. No current settlement restriction can be attributed to US 4,238,485 solely from the patent claims.

How does the patent compare with the underlying timolol patent estate?

The patent estate has to be divided between the active ingredient and the fixed-dose combination.

Patent subject	Covered subject matter	Relevance today
Timolol compound patents	Timolol chemical entity and related compounds	Expired
Timolol salt or formulation patents	Salt selection, dosage form, stability, or delivery	Depends on individual patent
US 4,238,485	Timolol-class beta blocker plus benzothiadiazine diuretic	Expired
Method patents	Combination treatment for hypertension	Expired for this patent
Manufacturing patents	Synthesis, crystallization, or processing	Requires separate patent-by-patent review

US 4,238,485 does not establish ownership of all timolol formulations. It is a combination patent. A competitor using timolol in an ophthalmic product, for example, would not ordinarily practice the claimed oral antihypertensive combination unless it also used the required thiazide component and ratio.

What manufacturing and intellectual-property barriers remain?

The patent does not claim a manufacturing process. It contains no apparent process limitation requiring:

A particular synthetic route.
A specific reaction solvent.
A crystallization step.
A particle-size distribution.
A tableting process.
A coating process.
A dissolution profile.
A specific impurity threshold.

Consequently, the patent would not have prevented independent manufacture of timolol, hydrochlorothiazide, or a noncovered dosage form after expiration.

Potential barriers during the patent term would have included:

Designing around the claimed beta-blocker structure.
Using a nonlisted diuretic.
Selecting a ratio outside the claimed range.
Selling the actives separately rather than as a covered composition.
Avoiding the claimed salt or stereoisomer.
Developing a formulation not satisfying the claimed tablet-strength limitations.

Those barriers are no longer enforceable under this patent.

Does biosimilar law apply?

No. Timolol and hydrochlorothiazide are small-molecule drugs, not biologics. The relevant FDA pathway is an abbreviated new drug application, not a biosimilar application under the Biologics Price Competition and Innovation Act.

The principal market-entry pathway for a generic fixed-dose product would be an ANDA demonstrating pharmaceutical equivalence and bioequivalence to the applicable reference product, subject to FDA requirements and any remaining unexpired patents or regulatory exclusivities. US 4,238,485 would not block that pathway today.

What is the competitive landscape for timolol-hydrochlorothiazide?

The combination competes with:

Timolol monotherapy.
Hydrochlorothiazide monotherapy.
Other beta blocker-thiazide combinations.
ACE inhibitor-thiazide products.
Angiotensin receptor blocker-thiazide products.
Calcium-channel blocker combinations.
Generic antihypertensive regimens using separate tablets.

The commercial value of the patent was strongest when fixed-dose combination products offered dosing convenience and a branded alternative to separate beta blocker and diuretic therapy. After patent expiration, generic substitution and separate-component prescribing materially reduced the patent's commercial leverage.

No current revenue right can be inferred from the expired patent. Any revenue exposure would have depended on the branded product's sales, the status of the relevant NDA, generic competition, and payer substitution.

How strong was the patent estate?

The patent was relatively strong for the specific fixed-dose combination described in claims 6 through 11, but narrower than a basic compound patent.

Strengths

Claims covered a clinically useful combination.
Claim 8 targeted the commercially relevant hydrogen maleate salt.
Claim 11 targeted a specific 10 mg/25 mg tablet.
The patent included both composition and method claims.
The broad genus in claim 1 could capture multiple related beta blockers.

Limitations

The patent did not claim timolol as a standalone molecule.
It required a thiazide component.
It required a defined weight ratio.
It did not claim manufacturing processes.
It did not cover every timolol dosage form.
It expired in 1997.
It did not create biologic-style interchangeability or biosimilar barriers.

The patent was commercially meaningful as a combination-product patent but is no longer a live exclusionary asset.

Key Takeaways

US Patent 4,238,485 covers antihypertensive compositions combining a defined beta blocker with a 1,2,4-benzothiadiazine diuretic.
Claims 6 through 11 narrow to timolol maleate and hydrochlorothiazide, including the commercially relevant 10 mg/25 mg tablet.
Claim 12 covers a listed group of thiazide and benzothiadiazine diuretics.
Claim 13 covers treatment of hypertension using the claimed combination.
The patent issued December 9, 1980 and ordinarily expired December 9, 1997.
The patent does not currently block generic entry, an ANDA, or manufacture of timolol or hydrochlorothiazide.
The patent is not a biosimilar matter because both active ingredients are small molecules.
Any current freedom-to-operate risk must arise from later, unexpired patents, regulatory exclusivity, trademarks, or product-specific formulation rights, not US 4,238,485.

FAQs About US Patent 4,238,485

Does US Patent 4,238,485 cover Timolide?

Yes. The patent's narrower claims correspond to the timolol maleate-hydrochlorothiazide combination associated with Timolide, particularly the 10 mg/25 mg tablet described in claim 11.

Can a generic manufacturer rely on patent expiration?

Yes. The patent's expiration removes its infringement risk. A generic manufacturer must still satisfy FDA approval requirements and review other potentially unexpired patents, but US 4,238,485 itself is no longer a barrier.

Does the patent cover timolol ophthalmic products?

No, not by its claims alone. The claims require combination with a 1,2,4-benzothiadiazine diuretic in a specified ratio. A timolol ophthalmic product without the claimed diuretic would not ordinarily meet those limitations.

Is hydrochlorothiazide alone covered by this patent?

No. The claims require both the beta blocker and the diuretic. Hydrochlorothiazide monotherapy does not satisfy the claimed composition.

Does the patent cover a fixed-dose combination using a different beta blocker?

Potentially, if the beta blocker falls within the claimed formula and the product satisfies the other limitations. A beta blocker outside that chemical genus would not fall within the literal scope of claim 1.

References

United States Patent No. 4,238,485. (1980, December 9). Antihypertensive compositions. United States Patent and Trademark Office.
United States Code, 35 U.S.C. § 154. Patent term.
United States Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations. Center for Drug Evaluation and Research.
United States Food and Drug Administration. (n.d.). Orange Book: Approved drug products with therapeutic equivalence evaluations. Center for Drug Evaluation and Research.
United States Food and Drug Administration. (n.d.). Drugs@FDA. Center for Drug Evaluation and Research.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
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Details for Patent: 4,238,485

Summary for Patent: 4,238,485