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How do you prepare a generic drug versus RLD comparison?
Compare the proposed product with the actual RLD using controlled evidence for both sides. Address active ingredient, route, dosage form and strength, then link labeling, formulation and BE assessments. Give each difference or unknown a supported disposition. The comparison organizes evidence of sameness and permitted differences; matching product names or numbers alone does not establish either.
Before you begin
ANDA administrative comparison under 314.94(a)(5)–(6), linked to scientific and labeling evidence.
What you will prepare: An annotated comparison that distinguishes established sameness, permitted differences and unresolved questions.
Use a comparison with evidence, not a column of yes answers
Set columns for attribute, proposed generic, RLD, source for each, difference and regulatory/scientific disposition. Start with active ingredient identity, route, dosage form and strength. Use the precise units and expression of strength; do not compare a salt quantity with active-moiety quantity without explaining the conversion.
Add relevant conditions of use and labeling cross-references without replacing the separate labeling comparison. Where product-specific composition questions matter, reference the controlled formulation and supporting CMC rationale. Do not invent the RLD's confidential quantitative formula or infer it from the label alone.
Explain differences at the correct level
A statement of active-ingredient sameness should point to the relevant identity evidence, not merely repeat a shared nonproprietary name. For a permitted difference supported by an approved suitability petition, identify the exact approval and explain how the proposed product stays within it. The ability to purchase or formulate a product does not establish that an ANDA is the correct pathway.
The administrative comparison is an index to evidence. It does not itself demonstrate bioequivalence, interchangeable labeling or acceptable quality. Link the BE strategy, quality data and labeling assessment, and identify which specialist owns each conclusion. Keep unresolved differences visible until their disposition is supported.
Worked review: identical numbers conceal different strength expressions
Fictional editorial exercise: both columns say “10 mg,” but one describes salt mass and the other active-moiety equivalent. The author marks strength as identical.
Obtain the approved strength expression and the proposed product's controlled composition. Reconcile units and scientific meaning, then have the regulatory owner confirm the comparison. If the RLD source is missing, leave the row unresolved. A neat table does not justify guessing the reference value.
Make every comparison row lead to a reviewable conclusion
Avoid a table whose only outcome is “same.” A reviewer needs the compared values, their sources and the meaning of any difference. Maintain separate statuses for supported sameness, a difference supported by an applicable pathway, and an unresolved question. These are editorial review statuses, not FDA classifications.
| Attribute | Proposed generic evidence | RLD evidence | Disposition to document |
|---|---|---|---|
| Active ingredient | Controlled identity and relevant CMC support | Approved ingredient identity and labeling | Same ingredient or the exact applicable approved-petition basis |
| Route and dosage form | Proposed product definition and labeling | Approved route and dosage form | Supported match or a specifically assessed difference |
| Strength | Exact expression, units and composition | Approved strength expression | Compare the same scientific quantity before deciding sameness |
| Conditions of use and labeling | Annotated proposed labeling | Currently approved RLD labeling | Cross-reference the separate labeling comparison and explain omissions |
| Inactive ingredients | Controlled formulation and amounts | Available authoritative formulation information | Identify product-category requirements and any justified difference; do not invent missing quantities |
| BE evidence | Study product identity and report, or waiver rationale | RLD identity and FDA-selected reference-standard record | Explain the scientific comparison and any distinct comparator role |
Under 314.94(a)(9), inactive-ingredient expectations vary by product category. For example, the regulation generally expects parenteral products to have the same inactive ingredients at the same concentrations, with specified possibilities for differences in preservative, buffer or antioxidant supported by appropriate evidence. Do not apply a general “generics may use different excipients” statement to every route. Equally, do not assume every excipient must always be identical for every product. Read the applicable provision and product-specific evidence.
Fictional strength exercise: the proposed composition lists a salt mass per unit, while the RLD label expresses the equivalent active-moiety amount. Put the exact source expressions into the table before normalizing anything. Add the documented chemical basis and calculation reviewed by the CMC owner, then show the comparable value. If the conversion basis or approved expression is missing, mark the row unresolved. Matching the printed number while changing what it measures produces a false sameness claim.
Fictional formulation exercise: FDA has selected a generic product as the reference standard, and the team copies that product's excipient list into the RLD column. The October 2020 guidance says the formulation comparison is against the RLD, even when the study reference standard differs. Restore the correct reference and identify any information gap. A comparator's public label cannot establish the confidential quantitative formula of another product.
For a petitioned ANDA, quote neither the team's requested difference nor a competitor's approval as if it were this application's permission. Identify the approved petition and explain how the proposed product remains within its scope. A permitted change does not remove the need for the remaining scientific and labeling evidence.
Review the table after formulation, labeling or reference-product changes. A row can become stale even when its wording still looks correct. Give the ANDA basis statement owner the final RLD identifiers and give the biowaiver request owner the controlled formulation version. That handoff prevents a sound comparison from being paired with an obsolete justification.
Your preparation checklist
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Frequently asked questions
Does the same active-ingredient name prove sameness for an ANDA?
A shared name is not the entire evidentiary assessment. Section 314.94 addresses information showing active-ingredient sameness and the relevant labeling references. Connect the administrative statement to controlled identity evidence, and assess any combination-product or approved-petition difference under its actual applicable provisions.
Should the comparison use the reference standard when it differs from the RLD?
Keep the roles separate. FDA’s guidance directs the labeling and formulation comparison to the RLD even when another product is selected as the reference standard for in-vivo BE testing. Identify the study comparator in its own record rather than silently substituting it in the RLD column.
Can all generic drug products use different inactive ingredients?
No single rule covers every product category. Section 314.94(a)(9) sets different provisions for parenteral, ophthalmic, otic and other products. Determine the applicable category, identify the actual qualitative and quantitative differences, and provide the required supporting assessment. A broad statement about generics is insufficient.
What should the table say when the RLD quantity or strength basis is unknown?
Show the exact available information and the unresolved question. Identify the evidence and owner needed to resolve it rather than filling the cell with an estimate and marking sameness. Public labeling and another product’s formula cannot establish an undisclosed RLD quantity; scientific and regulatory conclusions need an adequate basis.
Sources and revisions
Requirements, source recommendations and editorial preparation advice have different roles. Review the scope and revision of the source you use.
Regulation
21 CFR 314.94: content and format of an ANDA ↗Paragraphs (a)(3)–(6), (a)(8); eCFR current through September 18, 2026.
Guidance
Referencing Approved Drug Products in ANDA Submissions ↗October 2020 final guidance; III.B–D. Reopened September 22, 2026.
Technical specification · placement only
FDA eCTD v4.0 comprehensive hierarchy ↗Version 2.2, February 2025. Section 1.12.12. A heading identifies placement, not mandatory applicability.