Therapeutic Equivalence (Orange Book)
Therapeutic equivalence is the FDA designation indicating that a generic drug product is both pharmaceutically equivalent and bioequivalent to a reference brand-name drug, as published in the FDA's Orange Book with AB-rated approval codes.
Exam Tip
AB-rated = therapeutically equivalent, can substitute. B-rated = NOT equivalent, cannot substitute. Orange Book is the FDA reference. Know NTI drugs (warfarin, levothyroxine) may have extra restrictions on the ExCPT.
What Is Therapeutic Equivalence?
Therapeutic equivalence means that a generic drug can be expected to produce the same clinical effect and safety profile as its brand-name counterpart. The FDA publishes therapeutic equivalence evaluations in "Approved Drug Products with Therapeutic Equivalence Evaluations," commonly known as the Orange Book.
Requirements for Therapeutic Equivalence
A drug must meet ALL of the following:
| Requirement | Description |
|---|---|
| Pharmaceutical equivalence | Same active ingredient, dosage form, strength, and route of administration |
| Bioequivalence | Same rate and extent of absorption (AUC and Cmax within 80-125% of reference) |
| Adequate labeling | Compliant with FDA labeling requirements |
| cGMP compliance | Manufactured under current Good Manufacturing Practice |
| Same batch-to-batch consistency | Meets approved specifications |
Orange Book Rating Codes
| Code Prefix | Meaning |
|---|---|
| A | Therapeutically equivalent (can substitute) |
| B | NOT therapeutically equivalent (cannot substitute) |
Common A-Rated Codes
| Code | Meaning |
|---|---|
| AB | Bioequivalence demonstrated; most common for substitution |
| AA | No known or suspected bioequivalence problems (solutions, gases) |
| AP | Injectable aqueous solutions |
| AT | Topical products |
| AN | Solutions, aerosol (nasal) |
Common B-Rated Codes
| Code | Meaning |
|---|---|
| BC | Extended-release products NOT shown to be bioequivalent |
| BD | Documented bioequivalence problems |
| BP | Potential bioequivalence problems |
| BX | Insufficient data for determination |
Generic Substitution Rules
| Factor | Details |
|---|---|
| AB-rated | Can be substituted in all states (unless prescriber writes DAW) |
| B-rated | Cannot be automatically substituted |
| State laws | Most states require or permit generic substitution for AB-rated products |
| Narrow therapeutic index (NTI) | Some states restrict substitution for NTI drugs (warfarin, levothyroxine, phenytoin) |
Pharmacy Technician's Role
- Check Orange Book ratings when selecting generic alternatives
- Verify AB rating before generic substitution
- Apply correct DAW code on insurance claims
- Understand that B-rated products require specific prescriber approval to substitute
Exam Alert
Therapeutic equivalence is tested in both the Dispensing Process and Drugs/Drug Therapy domains. Key points: AB = can substitute, B = cannot substitute. Know that Orange Book ratings determine generic substitution and that NTI drugs may have additional state restrictions.
Study This Term In
Related Terms
DAW Codes (Dispense As Written)
DAW codes are standardized numeric codes (0-9) used on pharmacy claims to indicate whether a brand-name or generic drug should be dispensed and who is requesting the specific product.
NDC Number (National Drug Code)
The NDC (National Drug Code) is a unique 10-digit, 3-segment numeric identifier assigned to each medication product in the United States, identifying the labeler, product, and package size.
Formulary
A formulary is a list of prescription drugs approved for coverage by a health insurance plan, pharmacy benefit manager (PBM), or healthcare institution, organized into tiers that determine patient cost-sharing.
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