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Patent landscape, scope, and claims: |
United States Patent 5,456,925 Scope and Claims: Ranitidine–Bismuth Carboxylate Tablet Formulations and Alkaline-Salt Fast Disintegration
Executive summary: U.S. Patent 5,456,925 claims a tablet formulation built around a ranitidine–bismuth carboxylate (bismuth complexed with a carboxylic acid selected from tartaric acid or citric acid) plus a specific alkaline salt load (2–8% w/w) chosen from carbonates, bicarbonates, citrates, acetates, where the alkaline salt is selected and dosed to increase post-swallow disintegration and dissolution rate. Independent claim scope is constrained by (i) tablet dosage form, (ii) specific actives/complexes, (iii) relative composition bands, and (iv) an explicit function/efficacy limitation (“effective to increase” disintegration/dissolution after swallowing). Dependent claims narrow to dose ranges, % w/w of ranitidine bismuth carboxylate, enumerated ranitidine salt complex identities, and alkaline salt specific species (notably sodium carbonate).
What does US Patent 5,456,925 claim for ranitidine bismuth carboxylate tablets?
Core claim architecture: Claim 1 is a formulation claim with a tight composition definition and a post-administration performance function.
Independent claim 1 (composition and composition-effect limitations)
Claim 1 requires all of the following elements:
-
Dosage form and weight
- “pharmaceutical composition in tablet form”
- tablet weight: about 400 to about 900 mg
-
Chemical core
- salt formed between ranitidine and a complex of bismuth with a carboxylic acid selected from:
- tartaric acid
- citric acid
-
Alkaline salt excipient with a performance purpose
- effective amount of 2 to 8% w/w of an alkaline salt
- alkaline salt is selected from:
- carbonates
- bicarbonates
- citrates
- acetates
- limitation: amount is “effective to increase the rate of disintegration and dissolution … after swallowing by a patient”
-
Overall combination
- The alkaline salt is a required component, not optional, and is tied to the defined functional outcome.
Claim 1 practical scope statement (what falls inside):
- Any tablet (400–900 mg) containing ranitidine–bismuth carboxylate (tartarate or citrate-based bismuth complex) in combination with 2–8% w/w of a listed alkaline salt family member that is present in a quantity alleged to boost disintegration/dissolution in vivo.
Claim 1 practical scope statement (what falls outside):
- Anything outside the tablet weight band.
- Ranitedine–bismuth complexes where the carboxylic acid is not tartaric or citric (e.g., other bismuth carboxylates).
- Formulations where the alkaline salt is <2% or >8% w/w.
- Formulations substituting alkaline salts not in the enumerated families.
- Non-tablet dosage forms (capsules, syrups, powders).
- Uses where alkaline salt is present but not in the claimed “effective” amount for the disintegration/dissolution outcome.
Which alkaline salts and what percentage limits define infringement risk under claim 1?
Alkaline salt scope is broad in genus but narrow in percent and families.
Allowed alkaline salt classes
Claim 1 enumerates:
- carbonates
- bicarbonates
- citrates
- acetates
Critical quantitative band
- 2–8% w/w alkaline salt, “effective” for the disintegration/dissolution rate.
How dependent claims tighten alkaline salt species
- Claim 5: alkaline salt is selected from alkali metal and alkaline earth metal carbonates and bicarbonates and mixtures.
- Claim 6: alkaline salt is sodium carbonate and mixtures.
- Claim 7: ranitidine bismuth carboxylate is a specific citrate complex and alkaline salt is sodium carbonate.
- Claim 10: alkaline salt is at about 5% by weight.
Infringement mapping:
- A product with 2–8% of an allowed alkaline salt class can implicate claim 1.
- If the alkaline salt is restricted to carbonates/bicarbonates only (and especially sodium carbonate), claims 5–7 and 10 provide narrower footholds.
What are the ranitidine–bismuth carboxylate identities covered by the patent?
Claim 4 enumerates two specific bismuth complex embodiments, both tied to ranitidine salt formation.
Claim 4: enumerated ranitidine bismuth complex species
Claim 4 specifies:
- N-[2-[[[5-[(dimethylamino)methyl]-2-furanyl]methyl]thio]ethyl]-N'-methyl-2-nitro-1, 1-ethenediamine 2-hydroxy-1,2,3-propanetricarboxylate bismuth (3+) complex
- N-[2-[[[5-[(dimethylamino)methyl]-2-furanyl]methyl]thio]ethyl]-N'-methyl-2-nitro-1, 1-ethenediamine [R-(RR)]-2, 3-dihydroxybutanedioate bismuth (3+) complex
Practical interpretation of the enumerations:
- Both enumerated complexes correspond to the earlier claim 1 requirement that the bismuth complex is associated with a carboxylic acid selected from tartaric or citric acid.
- The first reads as the citric acid-based tricarboxylate; the second reads as the tartaric acid-based dihydroxybutanedioate.
Claim 7/9: explicit linking to citrate complex + sodium carbonate
- Claim 7: ranitidine bismuth carboxylate is the citric acid-based complex and alkaline salt is sodium carbonate.
- Claim 9: contains the same linkage to citric acid complex and sodium carbonate (claim redundancy suggests multiple fallback dependent claim strategies).
How do the ranitidine bismuth dose and loading limits narrow claim scope?
Dose range dependent claims
- Claim 2: 200 to 800 mg of ranitidine bismuth carboxylate per unit dose
- Claim 3: 50 to 95% w/w of ranitidine bismuth carboxylate
Specific alkaline salt and dose subrange
- Claim 10: alkaline salt about 5% by weight
- Claim 11: about 400 mg of ranitidine bismuth citrate
Scope impact
- Products that meet claim 1 but miss claim 2/3 are still potentially within claim 1.
- Products that match the alkaline salt and weight band but change the ranitidine bismuth carboxylate loading percentage may fall out of claims 2–3 while retaining exposure on claim 1 if within the functional genus boundaries.
What is the effective tablet weight envelope and why it matters?
Claim 1 fixes the tablet weight to about 400 to about 900 mg.
Scope consequences:
- If the same API/excipient blend is pressed into smaller or larger tablets outside the envelope, it can avoid claim 1 while still using the same chemical entities.
- If a generic attempts reformulation to change tablet size but keeps the same core chemistry and alkaline percentage, the exposure becomes dependent on whether an examiner/court treats “about” as flexible enough to cover the actual weight.
How broad is “increased disintegration and dissolution after swallowing” as a claim limitation?
Claim 1 ties alkaline salt quantity to performance:
- the alkaline salt is “effective to increase the rate of disintegration and dissolution after swallowing”.
Claim scope implications for a competitor:
- Simply including an alkaline salt within 2–8% may still be argued not to meet the functional outcome if the formulation does not achieve faster disintegration/dissolution “after swallowing.”
- Conversely, if the competitor’s formulation demonstrably increases disintegration/dissolution, the functional limitation can be satisfied even if the developer did not intend the same mechanism.
Tactical litigation note from a landscape perspective: A functional “effective to increase” term typically drives reliance on:
- dissolution/disintegration test evidence,
- in vivo surrogates or correlates,
- formulation-specific measurements tied to tablet properties.
How many claims are directly “composition-only” vs “composition plus excipients” in this patent?
From the provided claim set, the following are composition-defining and excipient-permissive:
Composition-only core
- Claim 1 is fully compositional with defined components and bands.
Excipient allowance
- Claim 8: “also containing one or more physiologically acceptable carriers or excipients.”
Scope effect:
- Competitors can add common excipients (binders, lubricants, disintegrants) without automatically exiting the claim.
- However, adding excipients does not remove the required elements: tablet weight band, ranitidine-bismuth carboxylate presence, alkaline salt at 2–8% and in allowed families.
What is the claim-by-claim scope map for infringement coverage?
| Claim |
Key additional limitations beyond claim 1 |
Narrowing axis |
| 1 |
Tablet; 400–900 mg; ranitidine–bismuth complex with tartaric or citric acid; alkaline salt 2–8% w/w from carbonates/bicarbonates/citrates/acetates; “effective to increase” disintegration/dissolution after swallowing |
Independent scope gate |
| 2 |
200–800 mg ranitidine bismuth carboxylate per unit dose |
API dose |
| 3 |
50–95% w/w ranitidine bismuth carboxylate |
API loading |
| 4 |
Two enumerated complex identities (citric-based tricarboxylate and tartaric-based dihydroxybutanedioate bismuth complexes) |
Chemical species |
| 5 |
Alkaline salt limited to alkali/alkaline earth carbonates and bicarbonates |
Salt genus narrowed |
| 6 |
Sodium carbonate |
Specific salt species |
| 7 |
Citric complex + sodium carbonate |
Combined species |
| 8 |
Allows physiologically acceptable carriers/excipients |
Excipients permitted |
| 9 |
Duplicates claim 7 structure (citric complex + sodium carbonate) |
Additional dependent fallback |
| 10 |
Alkaline salt about 5% w/w |
Specific loading |
| 11 |
About 400 mg ranitidine bismuth citrate |
Specific dose |
What generic entry risks exist for ranitidine bismuth carboxylate tablets under this claim set?
Primary entry risk profile
- A generic or follow-on tablet that uses the same API complex and includes an alkaline salt in the 2–8% band from the allowed families can face direct claim 1 exposure even if excipient package changes.
Secondary entry risk drivers
- Switching from sodium carbonate to another allowed alkaline species does not eliminate claim 1, but may impact dependent claims 5–7/10.
- Changing tablet weight outside 400–900 mg is one of the clearer design-around levers.
- Changing the bismuth carboxylate from citric/tartaric to a different carboxylic acid is another design-around lever, but it changes the chemical core and risks different regulatory/clinical positioning.
How does this patent constrain formulation freedom compared with typical ranitidine/bismuth competitors?
Compared with broader bismuth/acid formulations, claim 1 is restrictive in three ways:
- Chemical identity: bismuth carboxylate is tethered to citric or tartaric acid plus a ranitidine salt.
- Dosage form: must be a tablet within a narrow weight envelope.
- Disintegration/dissolution mechanism: alkaline salt amount is bound to a functional outcome after swallowing.
Key takeaways
- U.S. Patent 5,456,925 protects a tablet formulation combining ranitidine–bismuth carboxylate (citric or tartaric-derived bismuth complex) with 2–8% w/w of an alkaline salt (carbonates/bicarbonates/citrates/acetates) that is effective to increase disintegration and dissolution after swallowing.
- The independent claim is gated by tablet form and weight (about 400–900 mg) and a performance-based functional limitation tied to the alkaline salt quantity.
- Dependent claims narrow to:
- ranitidine bismuth carboxylate dose (200–800 mg) and loading (50–95% w/w),
- enumerated citric- and tartaric-based bismuth complex identities,
- alkaline salt species (notably sodium carbonate) and about 5% w/w,
- a specific target about 400 mg ranitidine bismuth citrate.
- Excipients are permitted (claim 8), so product differentiation via “standard excipient swaps” does not avoid core coverage if the required components and quantitative bands remain.
FAQs
-
Does claim 5 require only carbonates/bicarbonates, or does it also allow citrates/acetates?
Claim 5 restricts the alkaline salt to alkali/alkaline earth carbonates and bicarbonates (and mixtures), excluding citrates and acetates.
-
If a tablet uses sodium bicarbonate instead of sodium carbonate, is it still within the independent claim 1?
Yes. Sodium bicarbonate falls within claim 1’s allowed families (bicarbonates), subject to the 2–8% w/w limit and the functional disintegration/dissolution requirement.
-
Can a competitor add standard excipients and still infringe?
Yes. Claim 8 explicitly allows physiologically acceptable carriers or excipients, without modifying the required alkaline salt and ranitidine bismuth complex limitations.
-
What is the easiest design-around lever shown in the provided claims?
Changing the tablet weight outside about 400–900 mg or changing the bismuth carboxylate away from citric/tartaric are the clearest levers visible from the claim text.
-
Which dependent claims most closely target sodium carbonate formulations?
Claims 6, 7, 9, and 10.
References
No external sources were provided or cited in the prompt.
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