List of Excipients in Branded Drug DIPHENHYDRAMINE HCL

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Generic Drugs Containing DIPHENHYDRAMINE HCL

Company	Ingredient	NDC	Excipient
Redmont Pharmaceuticals LLC	diphenhydramine hydrochloride	71741-511	ALCOHOL
Redmont Pharmaceuticals LLC	diphenhydramine hydrochloride	71741-511	ANHYDROUS CITRIC ACID
Redmont Pharmaceuticals LLC	diphenhydramine hydrochloride	71741-511	D&C RED NO. 33
Redmont Pharmaceuticals LLC	diphenhydramine hydrochloride	71741-511	FD&C RED NO. 40
Redmont Pharmaceuticals LLC	diphenhydramine hydrochloride	71741-511	SODIUM CITRATE

What are the Most Frequently-Used Excipients in DIPHENHYDRAMINE HCL?

# Of NDCs	Excipient
1	ALCOHOL
1	ANHYDROUS CITRIC ACID
1	D&C RED NO. 33
1	FD&C RED NO. 40
1	SODIUM CITRATE

Diphenhydramine HCl Excipient Strategy and Commercial Opportunities

Last updated: August 29, 2026

Diphenhydramine hydrochloride is an established, low-cost active pharmaceutical ingredient used in antihistamine, nighttime sleep-aid, cough-and-cold, antiemetic, and topical products. Its principal commercial opportunity is not new chemical entity protection. It is differentiated delivery: alcohol-free liquids, sugar-free pediatric products, orally disintegrating formats, softgels, unit-dose sachets, preservative-reduced products, and combination products with clear consumer-use advantages.

The API is generally suited to immediate-release dosage forms. Excipient strategy should prioritize taste masking, physical stability, dose uniformity, preservative control, manufacturability, and age-appropriate dosing. Regulatory and patent barriers are relatively low compared with newer pharmaceutical products, but FDA monograph compliance, labeling, abuse-risk management, and formulation-specific intellectual property remain important.

What is diphenhydramine hydrochloride used for?

Diphenhydramine HCl is a first-generation H1 antihistamine with sedative and anticholinergic effects. In the United States, it is marketed in prescription and nonprescription products for allergy symptoms, nighttime sleep relief, cough-and-cold symptoms, motion sickness, and selected topical indications.

Common oral strengths include 25 mg and 50 mg. Pediatric liquid products commonly use lower concentrations, with dosing controlled by age and weight restrictions on the label. Topical products use materially different concentrations and excipient systems from oral products.

Product category	Typical dosage form	Primary commercial use	Key formulation issue
Allergy relief	Tablet, capsule, liquid	Oral antihistamine	Taste, dose uniformity, sedation labeling
Nighttime sleep aid	Tablet, softgel, liquid	Short-term sleep relief	Rapid release, swallowability, misuse prevention
Cough-and-cold combination	Liquid, tablet, capsule	Symptomatic relief	Compatibility with multiple APIs
Pediatric product	Oral solution or suspension	Age-restricted allergy or cold relief	Taste, preservative safety, dosing accuracy
Topical antipruritic	Cream, gel, spray	Itching and minor skin irritation	Local tolerability and penetration control
Travel-sickness product	Tablet, chewable	Motion sickness	Fast onset and portability

FDA OTC monograph conditions and product-specific labeling determine whether a diphenhydramine product can be marketed without an approved new drug application. The applicable requirements depend on indication, route, dosage form, strength, labeling, and active ingredient combination.[1]

Which excipients are most suitable for diphenhydramine HCl tablets and capsules?

Immediate-release tablets and capsules offer the lowest development risk. The formulation objective is usually rapid dissolution with adequate mechanical strength and acceptable mouthfeel.

Tablet excipient strategy

A conventional immediate-release tablet may use:

• Microcrystalline cellulose or dibasic calcium phosphate as filler
• Lactose, mannitol, or sorbitol for bulk and mouthfeel
• Crospovidone, croscarmellose sodium, or sodium starch glycolate as disintegrant
• Povidone or copovidone as binder
• Colloidal silicon dioxide as glidant
• Magnesium stearate or sodium stearyl fumarate as lubricant
• Film-coating polymers such as hypromellose or polyvinyl alcohol
• Titanium dioxide or approved colorants where permitted

Diphenhydramine HCl is used at a sufficiently high dose that content uniformity is generally less difficult than for highly potent low-dose drugs. The more important manufacturing risks are blend segregation, lubricant overmixing, tablet sticking, and dissolution changes caused by excessive hydrophobic lubrication.

A direct-compression platform can reduce processing steps. Wet granulation may be justified when the API-excipient blend has poor flow or compression performance. Dry granulation is an alternative where moisture exposure should be limited.

Capsule excipient strategy

Hard capsules can use a simpler blend based on microcrystalline cellulose, lactose, starch, crospovidone, colloidal silicon dioxide, and a lubricant. Capsule products support rapid development and can accommodate powder blends, pellets, or mini-tablets.

Softgels are commercially attractive for nighttime sleep products because they provide a smooth dosage form, support liquid or semisolid fills, and can improve swallowability. The shell typically contains gelatin or a vegetarian polymer, plasticizers such as glycerol or sorbitol, water, and colorants. The fill must be evaluated for shell compatibility, migration, brittleness, and long-term leakage.

What excipients improve diphenhydramine HCl liquid products?

Liquid products provide the strongest opportunity for formulation differentiation, particularly in pediatric, geriatric, and dysphagia markets. The main problems are bitterness, sedimentation, microbial control, dosing accuracy, and chemical stability.

Oral solution

An oral solution can include:

• Purified water
• Glycerin, sorbitol, or propylene glycol as cosolvent and humectant
• Sucrose or high-intensity sweeteners for taste
• Citric acid, citrate, phosphate, or other buffers
• Flavor systems such as cherry, grape, berry, or mint
• Sodium benzoate, potassium sorbate, or other permitted preservatives
• Chelating agents such as disodium EDTA where justified
• Colorants compatible with the target market

Alcohol-free formulations have a clear commercial advantage. They support broader household use and avoid the labeling and consumer concerns associated with ethanol-containing products. Sugar-free versions can use sorbitol, glycerin, sucralose, acesulfame potassium, or combinations of sweeteners. Excessive polyol content can create gastrointestinal tolerability problems, so the sweetener system requires dose-volume assessment.

The principal development challenge is taste masking. Diphenhydramine is strongly bitter and may leave a lingering sensory effect. Flavor alone may be inadequate. Useful approaches include polymeric taste-masking systems, ion-exchange resins, cyclodextrins, coated particles, and pH-controlled formulations. Each approach must preserve rapid release and avoid excessive viscosity or dose nonuniformity.

Oral suspension

A suspension can reduce the amount of dissolved bitter drug in the mouth and may improve palatability. Candidate excipients include:

• Microcrystalline cellulose and carboxymethylcellulose sodium
• Xanthan gum
• Hydroxypropyl methylcellulose
• Sodium carboxymethylcellulose
• Polysorbates or other wetting agents
• Structured vehicles such as glycerin or sorbitol
• Preservatives and buffers

A suspension must demonstrate redispersibility, sedimentation control, pourability, and dose uniformity after storage. The label should include a suitable shaking instruction. Unit-dose cups or oral syringes can reduce dosing error, particularly for pediatric products.

What formulation patents can protect diphenhydramine products?

The diphenhydramine molecule and its hydrochloride salt are long-established. Commercially relevant protection is therefore more likely to arise from formulation, delivery, packaging, or combination claims than from basic API composition claims.

Potentially protectable subject matter includes:

IP category	Example claim focus	Commercial value
Taste masking	Resin complexes, coated particles, polymer matrices	High for pediatric liquids and chewables
Modified release	Extended-release matrices or multiparticulates	Moderate, but must justify clinical and commercial need
Orally disintegrating tablets	Porous matrix, superdisintegrant system, fast dispersion	Moderate
Softgels	Fill composition, shell compatibility, dissolution profile	Moderate
Topical delivery	Gel, spray, film, emulsion, penetration control	Moderate
Combination products	Compatibility and stability of multiple APIs	Moderate to high
Preservative-free packaging	Unit-dose or sterile/nonsterile multidose system	Niche
Manufacturing process	Granulation, coating, particle engineering	Depends on enforceability and design-around risk

A formulation patent must provide a real technical distinction. Broad claims covering routine use of common sweeteners, binders, lubricants, or preservatives are vulnerable to enablement, written-description, obviousness, and design-around challenges. Trade-secret protection may be more practical for flavor systems, process parameters, and supplier-specific excipient blends.

What is the FDA regulatory status of diphenhydramine HCl?

Diphenhydramine HCl is an established FDA-regulated drug ingredient. Its regulatory pathway depends on the intended use.

OTC status

FDA OTC monographs address active ingredients and conditions for use in therapeutic categories such as antihistamines, nighttime sleep aids, and cough-and-cold products. A manufacturer must conform to the applicable monograph, labeling requirements, dosage restrictions, warnings, and general OTC rules.[1][2]

A product that falls outside monograph conditions may require an approved NDA or another applicable regulatory pathway. Combination products require particular attention to ingredient compatibility, permitted indications, dosing instructions, and duplicate-ingredient warnings.

Prescription products

Prescription diphenhydramine products can use dosage forms and indications outside OTC monograph conditions. A formulation change may require an approved supplement or new application depending on the product and the scope of the change.

Inactive ingredient review

Excipients should be screened against the FDA Inactive Ingredient Database and relevant compendial standards. The database provides precedent for route, dosage form, and maximum potency but does not automatically establish approval for every new formulation.[3] Excipient levels, route, patient population, and product use must remain within the applicable regulatory framework.

What is the Orange Book status of diphenhydramine HCl?

The Orange Book lists approved drug products and patent or exclusivity information where applicable. Diphenhydramine HCl products are predominantly mature generic or OTC products, and the commercial significance of any Orange Book listing must be assessed at the individual product level.[4]

For a new oral generic or prescription product, the relevant questions are:

1. Does the reference product have current listed patents?
2. Are any listed patents formulation, method-of-use, or drug-delivery patents?
3. Is pediatric exclusivity attached?
4. Does the applicant need a Paragraph IV certification?
5. Are the proposed labeling and dosage form identical or materially different from the reference product?

Because diphenhydramine has been marketed for decades, basic composition-of-matter exclusivity is not a meaningful barrier. The principal risks are product-specific patents, regulatory exclusivity, labeling differences, and litigation over a differentiated dosage form.

When does diphenhydramine HCl lose exclusivity?

Diphenhydramine HCl does not have a commercially relevant near-term loss-of-exclusivity event comparable to a modern branded small molecule. Its foundational chemical exclusivity expired long ago. Competition is already established across tablets, capsules, liquids, topical products, and combination medicines.

The relevant commercial timeline is therefore based on product entry and formulation differentiation rather than a single patent expiration date.

Exclusivity issue	Diphenhydramine HCl position
Basic compound protection	Expired
Generic competition	Established
OTC monograph access	Available only if product conditions are met
Product-specific formulation patents	Possible, but narrow and claim-dependent
Method-of-use patents	Possible for specific approved indications
Biosimilar exclusivity	Not applicable
Paragraph IV risk	Product-specific and generally limited to listed patents
Brand loyalty	Can remain important in pediatric, sleep, and combination segments

Are Paragraph IV challenges relevant to diphenhydramine products?

Paragraph IV litigation is relevant only when an ANDA applicant identifies an Orange Book-listed patent for the reference product and certifies that the patent is invalid, unenforceable, or will not be infringed. A generic applicant may also use other certifications depending on the patent and product circumstances.[5]

For mature diphenhydramine products, the greater practical risk is often not a basic API patent challenge. It is a challenge involving:

• A softgel fill composition
• A controlled-release dosage form
• A chewable or orally disintegrating tablet
• A combination product
• A specific method of treating insomnia, allergy, or motion sickness
• A formulation using a particular taste-masking or coating system

A company developing a differentiated product should conduct a product-by-product Orange Book and patent-family review rather than assume that the age of the API eliminates all IP exposure.

Is there biosimilar risk for diphenhydramine HCl?

No. Diphenhydramine HCl is a chemically synthesized small molecule, not a biologic. Biosimilar regulation under the Public Health Service Act does not apply. Competitive entry occurs through generic-drug, OTC, prescription, or monograph pathways rather than the biosimilar pathway.

Which commercial opportunities are strongest for diphenhydramine HCl?

The highest-value opportunities are dosage forms that solve a consumer or caregiver problem without introducing complex clinical requirements.

Alcohol-free and sugar-free liquids

These products can target families seeking easier-to-use formulations. Differentiation depends on taste, dosing accuracy, packaging, and label clarity. A calibrated oral syringe is more defensible commercially than a conventional measuring cup alone.

Pediatric taste-masked products

Taste masking can support premium positioning, but pediatric use requires strict attention to age restrictions, dosing instructions, excipient exposure, and accidental-ingestion risk. The product should not create a dosing or sedative-risk perception that conflicts with its intended market.

Orally disintegrating tablets

ODTs can target adults with swallowing difficulty and consumers seeking portable nighttime products. Mannitol, crospovidone, low-substituted hydroxypropyl cellulose, and flavor systems are common development tools. Mechanical strength, friability, moisture sensitivity, and mouthfeel require optimization.

Softgels

Softgels can differentiate a mature ingredient through appearance, swallowability, fill uniformity, and premium packaging. Their main technical risks are shell-fill interaction, leakage, oxygen and moisture transmission, and dissolution performance.

Topical gel and spray products

Topical diphenhydramine products can target localized itching. A gel or spray may offer a cleaner application than a cream, but penetration, irritation, application frequency, and warnings require careful evaluation. Topical products should not be assumed to have the same regulatory status as oral antihistamine products.

Combination products

Combination products can create retail differentiation but carry higher regulatory and manufacturing risk. Common combinations may include analgesics, antacids, cough suppressants, decongestants, or other cold-and-flu ingredients. The principal risks are duplicate active ingredients, additive sedation, dose complexity, stability interactions, and label congestion.

How strong is the patent estate for diphenhydramine HCl?

The foundational patent estate is weak because the compound is old and widely genericized. A new product can still obtain meaningful protection if it has a technically specific and commercially useful formulation.

Patent strength is highest when the product has:

• A defined particle or coating architecture
• Demonstrated taste-masking performance
• A measurable dissolution or pharmacokinetic advantage
• A non-obvious excipient ratio or processing sequence
• A dosage form that solves a clinically relevant administration problem
• Data supporting stability, bioavailability, or tolerability

Patent strength is lower when claims rely only on selecting common excipients from known alternatives. A formulation strategy should combine patent claims with trade secrets, distinctive packaging, trademarks, supply agreements, and regulatory execution.

How should manufacturers select excipients and suppliers?

Manufacturers should use a risk-ranked excipient selection process covering:

1. FDA inactive-ingredient precedent
2. USP-NF or equivalent compendial status
3. Pharmacopoeial impurity limits
4. Residual solvents and elemental impurities
5. Microbial limits and preservative performance
6. Global acceptability for target markets
7. Supply continuity and dual sourcing
8. Compatibility with manufacturing equipment
9. Stability under intended packaging
10. Labeling and allergen implications

For liquids, packaging is part of the excipient strategy. High-density polyethylene, polyethylene terephthalate, glass, child-resistant closures, induction seals, and unit-dose systems can materially affect sorption, leachables, oxygen exposure, and shelf life.

What generic launch scenarios exist for diphenhydramine HCl?

A conventional tablet or capsule faces immediate price competition. A differentiated launch is more viable when it targets a defined gap:

Launch scenario	Competitive position	Main risk
Standard 25 mg tablet	Low-cost, high-volume	Commodity pricing
Alcohol-free liquid	Household and pediatric appeal	Taste and preservative stability
Sugar-free liquid	Specialty retail and dietary positioning	Polyol tolerability
ODT	Convenience and swallowing benefit	Moisture and packaging
Softgel	Premium OTC positioning	Manufacturing cost
Taste-masked chewable	Pediatric and travel use	Palatability validation
Preservative-reduced unit dose	Sensitive-user niche	Packaging cost
Combination cold product	Retail differentiation	Regulatory and safety complexity
Topical gel or spray	Application convenience	Monograph and local tolerability issues

Key Takeaways

• Diphenhydramine HCl is a mature, highly genericized small molecule with no biosimilar pathway.
• The strongest commercial opportunities are formulation-led: alcohol-free liquids, sugar-free products, taste-masked pediatric formats, ODTs, softgels, and topical delivery systems.
• The main technical challenge is bitterness in oral products, followed by preservative control, dose uniformity, and physical stability.
• Basic API patents are not a meaningful commercial barrier. Formulation, delivery, manufacturing, packaging, and method-of-use claims can still create narrower protection.
• OTC monograph compliance, FDA inactive-ingredient precedent, product labeling, and dosage-form-specific requirements determine regulatory feasibility.
• Standard tablets face commodity pricing. Premium opportunities require a measurable administration or consumer-use advantage.
• Trade secrets and commercial execution may provide more durable value than broad formulation patent claims based on routine excipient selection.

FAQs

Can diphenhydramine HCl be formulated as a preservative-free oral liquid?

Yes. A preservative-free product may use unit-dose packaging, sterile manufacturing where appropriate, reduced-use packaging, or a validated formulation and container system. The commercial benefit must justify higher packaging and manufacturing costs.

Which sweetener is best for diphenhydramine HCl?

No single sweetener is universally optimal. Sucrose provides bulk and familiar taste, while sucralose, acesulfame potassium, sorbitol, and glycerin support sugar-free products. A combination system is often required to address bitterness, aftertaste, and viscosity.

Is an extended-release diphenhydramine product commercially attractive?

Potentially, but the opportunity is limited. Extended release would need to provide a clear benefit over inexpensive immediate-release products while addressing sedation, next-day impairment, dose accumulation, and abuse-risk concerns.

Can a diphenhydramine formulation receive patent protection?

Yes. Protection may cover taste masking, particle coating, ODT architecture, softgel fills, topical delivery, controlled release, combination stability, manufacturing processes, or packaging. The claims must be technically specific and supported by data.

Does diphenhydramine HCl require a new drug application for every new dosage form?

No. The pathway depends on the indication, route, strength, labeling, formulation, reference product, and OTC monograph status. Some products may qualify under monograph conditions, while others may require an NDA, ANDA, supplement, or another FDA submission.

References

1. U.S. Food and Drug Administration. (2024). Code of Federal Regulations, Title 21, Part 341: Cold, cough, allergy, bronchodilator, and anti-asthmatic drug products for over-the-counter human use. https://www.ecfr.gov/

2. U.S. Food and Drug Administration. (2024). Code of Federal Regulations, Title 21, Part 338: External analgesic drug products for over-the-counter human use. https://www.ecfr.gov/

3. U.S. Food and Drug Administration. (2024). Inactive Ingredient Database. https://www.accessdata.fda.gov/scripts/cder/iig/index.cfm

4. U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book. https://www.fda.gov/drugs/drug-approvals-and-databases/approved-drug-products-therapeutic-equivalence-evaluations-orange-book

5. U.S. Food and Drug Administration. (2024). Guidance for industry: 180-day exclusivity when multiple first applicants are eligible for approval. https://www.fda.gov/regulatory-information/search-fda-guidance-documents/180-day-exclusivity-when-multiple-first-applicants-are-eligible-approval