Scope and Claims Analysis for US Patent 4,628,051 (Triphasic Oral Contraceptives Using Low-Dose 17α-Ethinylestradiol and Norethindrone-Variant Progestogens)
US 4,628,051 claims a triphasic (21-unit) oral contraceptive regimen defined by (i) fixed estrogen daily equivalence across three active phases and (ii) phase-escalating progestogen doses across the same three phases, followed by an estrogen/progestogen-free interval. The patent’s enforceable core is sequence- and dosage-parameter-specific method claims and corresponding manufactured “triphasic unit” claims.
What exactly does US 4,628,051 claim: triphasic oral contraception method and product unit?
Featured-snip answer: The patent claims a 21-day triphasic oral contraceptive where 17α-ethinylestradiol equivalence is the same each phase (0.02–0.05 mg/day) while norethindrone (or specified progestogen variants) increases across phase 1 → phase 2 → phase 3, followed by 6–8 days without hormones.
Claim 1: method of contraception with phase-dependent progestogen escalation
Claim 1 is the foundational method claim and includes:
- 21 successive days of administration to a female of childbearing age.
- Three active phases with distinct dosing windows:
- First phase: 5–8 days
- Estrogen daily dosage equivalence: 17α-ethinylestradiol 0.02–0.05 mg/day
- Progestogenic activity equivalence: norethindrone 0.065–0.75 mg/day
- Second phase: 7–11 days
- Same estrogen equivalence: 0.02–0.05 mg/day
- Progestogenic activity equivalence: norethindrone 0.250–1.0 mg/day
- Third phase: 3–7 days
- Same estrogen equivalence: 0.02–0.05 mg/day
- Progestogenic activity equivalence: norethindrone 0.35–2.0 mg/day
- Followed by 6–8 days without estrogen and progestogen administration.
- Constraint: “provided that the estrogen daily dosage is the same for each period.”
- Administration concept: “administering … a combination of an estrogen and a progestogen” (with dependent claims narrowing routes, admixture, and selected identities).
Claim 2: oral administration and seven-day phases
Claim 2 narrows claim 1 by requiring:
- Oral administration of estrogen and progestogen.
- Each phase specified in claim 2 is seven days (i.e., a canonical 7-7-7 triphasic structure within the 21-day active period).
Claim 3: admixture
Claim 3 narrows to:
- Estrogen and progestogen are administered “in admixture” (i.e., co-formulated in the same unit per day).
Claims 4–6: selectable progestogen and estrogen identities
- Claim 4: Progestogen belongs to a closed list including:
- D-norgestrel
- Δ15 levonorgestrel and multiple Δ15 levonorgestrel derivatives
- norethindrone
- progesterone
- D-17β-acetoxy-13β-ethyl-17α-ethinyl-gon-4-en-3-one oxime (a specific progestin variant)
- Claim 5: Estrogen belongs to a closed list including:
- 17α-ethinylestradiol
- mestranol
- estrone
- estrone sulfate / salt
- estradiol
- estriol
- Claims 6 and 8–9: narrow combinations, including:
- estrogen = 17α-ethinylestradiol and progestogen = norethindrone (claim 6)
- estrogen and progestogen involving the D-17β-acetoxy… oxime (claims 8 and 9)
Claim 10 and 11–12: explicit dosage exemplars
- Claim 10: gives one explicit numeric set (with 0.035 mg estrogen per 7-day period and progestogen escalating 0.5 mg → 0.75 mg → 1.0 mg).
- Claim 11: explicitly recites a 7-day structured schedule:
- 7 days: 0.035 mg EE + 0.50 mg norethindrone
- 7 days: 0.035 mg EE + 0.75 mg
- 7 days: 0.035 mg EE + 1.0 mg
- then 7 days hormone-free
- Claim 12: provides explicit numeric dosing for estrogen = 0.035 mg EE and progestogen = the specific D-17β-acetoxy… oxime with escalating amounts:
- 0.180 mg → 0.215 mg → 0.250 mg across phases
- then 7 days hormone-free
Claim 1’s “real-world” infringement shape
To infringe claim 1 literally, an accused regimen must match the parameter geometry:
- Triphasic dosing totaling 21 consecutive days with the phase lengths within the claim windows (5–8 / 7–11 / 3–7).
- Estrogen fixed equivalence across phases (same daily dosage equivalence for all three phases).
- Progestogen dose escalation with phase-specific ranges relative to norethindrone activity.
- Hormone-free interval of 6–8 days.
Which formulations are captured: fixed-estrogen triphasic dosing with specific progestogen classes?
The patent captures a formulation design pattern rather than a single marketed product.
Estrogen scope
- Closed estrogen identity list in claim 5 (including EE and estrone-family estrogens).
- Claims 6, 16, 21, 23–24 explicitly anchor on:
- 17α-ethinylestradiol and/or
- 17α-ethinylestradiol 3-methyl ether.
Progestogen scope
The progestogen list in claim 4 is broad, covering multiple stereoisomeric and derivative forms. Two categories matter for designing-around:
- Norethindrone-path: claim 1’s ranges are expressed in “progestogenic activity … corresponding … to … norethindrone” and multiple dependent claims specify norethindrone as the progestogen.
- Oxime variant-path: claims 8–9 and 12, 20, 22, 24 specify D-17β-acetoxy-13β-ethyl-17α-ethinyl-gon-4-en-3-one oxime with explicit escalating phase doses.
Core constraint that drives product infringement
Across the triphasic day blocks, the estrogen daily dosage is the same in all three phases. Regimens that vary estrogen across phases are positioned outside the “provided that” constraint in claim 1 and its product analogues.
What patents protect in US 4,628,051’s claimed space: method claims vs “triphasic oral contraceptive unit” product claims?
Featured-snip answer: The estate claims both (i) how the drug is administered (method) and (ii) a manufactured dosage-unit package structure (unit) consisting of 21 separate units with defined compositions per day-block.
Claim 13: triphasic oral contraceptive unit with 21 separate dosage units
Claim 13 recasts claim 1 as a product configuration:
- Triphasic unit of 21 separate dosage units, adapted for successive daily oral administration.
- Three “phase” sub-sets:
- First phase: 7 units containing estrogen + progestogen at EE-equivalent 0.02–0.05 mg and norethindrone-equivalent 0.065–0.75 mg.
- Second phase: 7 units containing EE-equivalent 0.02–0.05 mg and norethindrone-equivalent 0.25–1.0 mg.
- Third phase: 7 units containing EE-equivalent 0.02–0.05 mg and norethindrone-equivalent 0.35–2.0 mg.
- Optional addition: 7 dosage units free of estrogen and progestogen.
- Same controlling constraint: estrogen daily dosage is the same in all three phases.
Claims 14–19: unit narrowing (tablets + estrogen/progestogen selection)
- Claim 14: dosage units are tablets.
- Claim 15: estrogen selection list (mirrors claim 5).
- Claim 16: estrogen specifically 17α-ethinylestradiol.
- Claim 17: estrogen specifically 17α-ethinylestradiol 3-methyl ether.
- Claim 18: progestogen selection list (mirrors claim 4).
- Claim 19: progestogen specifically norethindrone.
- Claim 20: progestogen specifically the oxime variant.
Claims 21–22: specific combinations
- Claim 21: EE 3-methyl ether + norethindrone.
- Claim 22: EE 3-methyl ether + oxime variant.
Claims 23–24: explicit numeric composition equivalents for each phase
- Claim 23: estrogen fixed at 0.035 mg EE each phase; progestogen:
- 0.50 mg norethindrone (phase 1)
- 0.75 mg norethindrone (phase 2)
- 1.0 mg norethindrone (phase 3)
- Claim 24: estrogen fixed at 0.035 mg EE; progestogen:
- 0.180 mg oxime variant
- 0.215 mg oxime variant
- 0.250 mg oxime variant
Claim 25: flexible phase lengths version of the “unit” claim
Claim 25 broadens from the strict 7-7-7 structure:
- 5–8 units (phase 1) with norethindrone-equivalent 0.065–0.75 mg
- 7–11 units (phase 2) with norethindrone-equivalent 0.25–1.0 mg
- 3–7 units (phase 3) with norethindrone-equivalent 0.35–2.0 mg
- optionally 6–8 units free of estrogen/progestogen
- estrogen daily dosage same across phases
How broad are the claim ranges: where do design-arounds likely sit?
The patent is range-based, so practical noninfringement is often about moving outside a numerical band or breaking a structural condition.
Key infringement-sensitive parameters
- Estrogen daily equivalence must stay within 0.02–0.05 mg/day (and be the same across phases).
- Progestogen activity equivalence must match the three phase-specific ranges (norethindrone-equivalence).
- Phase lengths (in claim 1 and 25) must fit the 5–8 / 7–11 / 3–7 windows.
- Hormone-free interval must be 6–8 days (claim 1) or optional 6–8 in claim 25.
- “Admixture” and “tablets” apply only when those dependent claims are asserted; claim 1 and 13 are not limited to those.
Design-around levers implied by claim text
- Change estrogen across phases (break the “same estrogen daily dosage” condition).
- Use a progestogen whose dose does not map into the norethindrone-equivalent bands across the three phases.
- Alter the day-count geometry (phase lengths outside the specified windows).
- Extend or shorten hormone-free days outside 6–8 (for claim 1).
How does the patent landscape likely map to this estate: method vs product claims and numeric exemplars?
The internal structure of US 4,628,051 suggests a two-layer protection strategy common in hormonal regimen patents:
- Broad regimen method capture (claim 1 + range logic).
- Product form capture (claim 13 + “triphasic unit” physical packaging configuration), plus explicit exemplars (claims 10, 11, 12, 23, 24).
Why this matters for licensing and litigation posture
- Manufacturers and labelers can be pulled into disputes through method-use framing (claim 1) and through product configuration (claim 13/25).
- Numeric exemplar claims (11, 12, 23, 24) make it easier to target a specific accused product with a clear dosing chart.
Claim chart style mapping (high-level) for infringement triage
Below is a structured mapping of each claim to “what must be true” in an accused regimen.
| Accused product/regimen element |
Claim 1 (method) |
Claim 13 (unit/product) |
| Female of childbearing age receives hormones in triphasic pattern |
Yes (method) |
Yes (adapted for successive daily oral administration) |
| Total active dosing = 21 consecutive days |
Yes |
Yes (21 separate dosage units for successive daily administration) |
| Phase lengths |
5–8 / 7–11 / 3–7 |
7 / 7 / 7 |
| Estrogen daily dosage equivalence |
0.02–0.05 mg, same across phases |
0.02–0.05 mg, same across all three phases |
| Progestogen activity escalation (norethindrone-equivalent) |
0.065–0.75 → 0.250–1.0 → 0.35–2.0 |
0.065–0.75 → 0.25–1.0 → 0.35–2.0 |
| Hormone-free interval |
6–8 days |
Optional 7 hormone-free units in claim 13; 6–8 in claim 25 |
| Route and co-formulation |
Dependent (claim 2, 3) |
Dependent (claim 14 tablets; admixture is embedded in “containing … in admixture”) |
| Specific estrogen/progestogen identities |
Dependent |
Dependent |
What is the practical scope of progestogen identity coverage (norethindrone vs oxime variant)?
Two dependent claim sets create distinct “identity lanes.”
Lane A: norethindrone-specific
- Claim 6 (EE + norethindrone)
- Claim 10, 11 (explicit norethindrone doses)
- Claim 19, 23 (unit composition with norethindrone)
Lane B: D-17β-acetoxy… oxime-specific
- Claim 8–9 (EE or EE 3-methyl ether + oxime)
- Claim 12 (explicit oxime dose escalation)
- Claim 20, 22, 24 (unit composition with oxime)
This split is material for patent infringement analysis because the “activity equivalence” language in claim 1 and product claims allows mapping to norethindrone activity, but identity-dependent claims can narrow to exact progestogen chemicals.
When does US 4,628,051 lose exclusivity?
No complete exclusivity timeline can be produced from the claim text alone. The expiration of a US patent depends on its filing date, priority chain, term adjustments, and any terminal disclaimers, none of which are included in the provided record.
What generic entry risks exist for the triphasic EE/norethindrone regimen space?
No Orange Book status or FDA regulatory pathway data is included in the provided information, so a Paragraph IV risk assessment cannot be grounded in facts here.
Key Takeaways
- US 4,628,051 protects a triphasic low-estrogen oral contraceptive regimen built on constant estrogen equivalence (0.02–0.05 mg EE/day) across phases and phase-escalating progestogen (norethindrone-equivalent) doses across three active blocks, followed by a hormone-free interval.
- The claims cover both method of contraception (claim 1 and dependents) and a manufactured triphasic oral contraceptive unit (claim 13 and dependents), increasing enforcement leverage against product configuration and dosing instructions.
- Litigation targeting is likely to focus on numeric exemplar claims (notably claims 10, 11, 12, 23, 24) because accused products have fixed phase dose tables that can be compared directly to the claim charts.
- The most direct design-around routes are to break the “same estrogen daily dosage across phases” condition and/or move dosing schedules outside the specified phase-length and hormone-free interval windows.
FAQs
- How do the claim ranges interpret “norethindrone-equivalent progestogenic activity”?
- Does using a different estrogen identity avoid infringement if the estrogen daily equivalence stays within 0.02–0.05 mg EE?
- Can a regimen with estrogen varied across phases avoid claim 1 and claim 13?
- Are “admixture” and “tablets” limitations required for infringement of the independent claims?
- How do claims 1 vs 25 differ for phase-length and hormone-free interval flexibility?
References
- United States Patent No. 4,628,051.
