List of Excipients in Branded Drug DILTIAZEM HYDROCHLORIDE EXTENDED-RELEASE

Generic Drugs Containing DILTIAZEM HYDROCHLORIDE EXTENDED-RELEASE

Company	Ingredient	NDC	Excipient
AvKARE	diltiazem hydrochloride	42291-028	BLACK CURRANT
AvKARE	diltiazem hydrochloride	42291-028	DIETHYL PHTHALATE
AvKARE	diltiazem hydrochloride	42291-028	FD&C RED NO. 40
AvKARE	diltiazem hydrochloride	42291-028	GELATIN
AvKARE	diltiazem hydrochloride	42291-028	HYPROMELLOSE
AvKARE	diltiazem hydrochloride	42291-028	METHACRYLIC ACID - METHYL METHACRYLATE COPOLYMER

What are the Most Frequently-Used Excipients in DILTIAZEM HYDROCHLORIDE EXTENDED-RELEASE?

# Of NDCs	Excipient
4	BLACK CURRANT
4	DIETHYL PHTHALATE
4	FD&C RED NO. 40
4	GELATIN
4	HYPROMELLOSE
4	METHACRYLIC ACID - METHYL METHACRYLATE COPOLYMER

# Diltiazem Hydrochloride Extended-Release Excipient Strategy and Commercial Opportunities

Last updated: August 24, 2026

Diltiazem hydrochloride extended-release products compete through release control, food-effect performance, capsule or tablet usability, dose flexibility, and manufacturing cost. The active ingredient is off-patent and widely genericized, so commercial value depends on differentiated delivery systems rather than chemical exclusivity. The strongest opportunities are sprinkle-capable capsules, robust alcohol-resistance, lower-cost multiparticulate manufacturing, and clinically meaningful once-daily formulations.

What is the commercial profile of diltiazem hydrochloride extended-release?

Diltiazem hydrochloride is a calcium-channel blocker approved for hypertension and chronic stable or vasospastic angina. Immediate-release diltiazem requires multiple daily doses, while extended-release products generally provide once-daily administration.

Attribute	Commercial significance
Active ingredient	Diltiazem hydrochloride
Therapeutic class	Non-dihydropyridine calcium-channel blocker
Main indications	Hypertension and angina
Common extended-release strengths	120, 180, 240, 300 and 360 mg, depending on product
Administration	Generally once daily
Dosage forms	Extended-release capsules and tablets
Reference products	Cardizem CD, Tiazac, Dilacor XR and Cardizem LA-type products
Primary generic pathway	ANDA for products matching a reference listed drug
Key regulatory tests	Comparative dissolution, fasting and fed bioequivalence, dose proportionality where applicable
Principal commercial barriers	Release-profile matching, food effect, manufacturing consistency and product-specific substitution status

Diltiazem undergoes extensive first-pass metabolism and has a relatively short immediate-release half-life, which supports modified-release development. The drug is also subject to CYP3A4-mediated interactions and has clinically relevant cardiac conduction effects. Release control must therefore avoid excessive early exposure and preserve adequate exposure through the dosing interval.[1]

What excipients are used in diltiazem extended-release products?

Diltiazem extended-release products generally use one of three excipient architectures: coated multiparticulates, hydrophilic or insoluble matrix tablets, or combinations of immediate-release and extended-release populations.

Multiparticulate capsule systems

Multiparticulate capsules contain drug-loaded beads or pellets with polymeric release coatings. The pellets may use sugar spheres, microcrystalline cellulose or other inert cores. The active layer commonly uses a binder such as povidone or hydroxypropyl cellulose. Release is controlled by an outer polymer coating.

Typical excipient functions include:

Function	Representative excipient classes
Inert core	Sucrose spheres, microcrystalline cellulose
Binder	Povidone, hydroxypropyl cellulose
Film former	Ethylcellulose, hypromellose
Permeability modifier	Methacrylate copolymers, pore-forming polymers
Plasticizer	Polyethylene glycol, triethyl citrate
Anti-tacking agent	Talc, colloidal silicon dioxide
Capsule shell	Gelatin or hypromellose
Colorant and opacity	Titanium dioxide, approved colorants

The commercial advantages are dose flexibility and the ability to combine bead populations with different coating thicknesses. The system can also support capsule opening and sprinkling if the beads remain intact and the label permits that use.

The disadvantages are higher process complexity, greater coating-equipment requirements and sensitivity to coating uniformity. Small changes in polymer weight gain, curing conditions, residual solvent and pellet size distribution can alter dissolution.

Matrix tablet systems

Matrix tablets embed diltiazem in a polymeric or wax-based system. Hydrophilic matrices commonly use hypromellose or related cellulose ethers. Insoluble matrices may use ethylcellulose, acrylic polymers or lipid excipients.

Hydrophilic matrix tablets are generally less expensive to manufacture than multiparticulates. They can be compressed using conventional equipment and scaled through established high-shear granulation, dry granulation or direct-compression processes.

Their principal risks are:

• Food-dependent swelling or erosion.
• Dose dumping under high mechanical stress.
• Incomplete dose delivery at the end of the release period.
• Sensitivity to tablet hardness, porosity and compression force.
• Difficulty reproducing the reference product's dissolution curve across multiple media.

A matrix tablet is often commercially attractive when the target product is a tablet-based reference listed drug. It is less attractive when the reference product uses a bead-based capsule and the sponsor cannot demonstrate equivalent in vivo performance.

Mixed-population systems

A mixed-population system combines immediate-release particles with one or more extended-release populations. This design can provide a loading phase followed by maintenance exposure.

The approach creates additional formulation variables, including:

• Immediate-release to extended-release dose ratio.
• Number of polymer coating populations.
• Relative dissolution rates.
• Stability of each population.
• Capsule fill-weight control.

Mixed-population technology can support a differentiated pharmacokinetic profile, but an ANDA applicant must still match the reference product sufficiently for bioequivalence and product-specific substitution. A clinically different profile may require a 505(b)(2) strategy rather than a conventional ANDA.

What excipient strategy best fits a new diltiazem extended-release product?

The most commercially practical strategy is usually a low-solubility polymer-coated multiparticulate system or a robust hydrophilic matrix tablet, selected according to the intended reference product and regulatory pathway.

Strategy 1: Low-cost matrix tablet

A matrix tablet is appropriate when the target is a tablet reference product and the sponsor prioritizes manufacturing efficiency.

The development focus should be:

1. Polymer grade and viscosity.
2. Drug-to-polymer ratio.
3. Tablet porosity and hardness.
4. Fasting and fed dissolution.
5. Alcohol challenge testing.
6. Stability under high humidity.
7. Scale-up control of granule density and compression force.

A high-viscosity hypromellose matrix can reduce manufacturing cost, but excessive polymer can delay release and produce a dissolution profile that differs from the reference. A lower polymer level may produce an initial burst or insufficient late-period release.

Strategy 2: Coated multiparticulate capsule

A coated-pellet capsule is appropriate when the sponsor seeks sprinkle capability, dose flexibility or a profile closer to established capsule products.

The development focus should be:

1. Narrow pellet-size distribution.
2. Uniform drug-layering efficiency.
3. Consistent polymer weight gain.
4. Controlled curing of acrylic or ethylcellulose films.
5. Capsule fill-weight precision.
6. Prevention of pellet agglomeration.
7. Retention of release performance after capsule opening.

This strategy has a higher cost base but offers more control over the release curve. It also permits multiple pellet populations, which can help match complex reference-product profiles.

Strategy 3: Excipient-enabled differentiation

A sponsor can create commercial differentiation through excipient selection without changing the active ingredient. Potential attributes include:

• Sprinkle administration for patients with swallowing difficulty.
• Lower pill burden through strength rationalization.
• Reduced food effect.
• Improved physical stability in high humidity.
• Lower alcohol-induced release acceleration.
• Color-coded strengths for medication management.
• Reduced use of lactose or gelatin for selected markets.
• More consistent capsule opening and pellet recovery.

The strongest claims must be supported by labeling, comparative clinical data or validated performance testing. Excipient novelty alone generally does not create durable market protection.

What formulations are protected by diltiazem extended-release patents?

The original diltiazem compound is an established generic active ingredient. Any remaining intellectual-property value is more likely to arise from dosage-form design, release kinetics, manufacturing processes, particle engineering or specific methods of use than from the active molecule.

Potentially protectable subject matter includes:

IP category	Potential claim focus
Formulation	Polymer matrix, coated pellets or multilayer dosage form
Release profile	Defined dissolution windows or pharmacokinetic parameters
Sprinkle product	Capsule-opening and food-administration configuration
Manufacturing	Drug layering, coating, curing or compression process
Stability	Moisture-control or impurity-reduction system
Method of use	Specific dosing regimens or patient populations
Combination product	Diltiazem with another cardiovascular agent

Patent relevance is product-specific. Cardizem CD-type capsules, Tiazac-type capsules and Cardizem LA-type tablets may have different reference products, labeling and historical patent positions. Current Orange Book listings must be reviewed by reference product, strength and dosage form before relying on any patent conclusion.[2]

When does diltiazem extended-release lose exclusivity?

Diltiazem hydrochloride extended-release products have generally operated in a mature generic market. Compound exclusivity for diltiazem has expired, and the commercial market is primarily governed by ANDA approvals, product-specific patents and regulatory exclusivities.

Exclusivity category	Current commercial effect
Active-ingredient exclusivity	Expired for diltiazem hydrochloride
Original extended-release product exclusivity	Historical and expired for major products
Product-specific formulation patents	Must be checked in the Orange Book and patent records
Pediatric exclusivity	Not generally a central barrier for mature products
Orphan exclusivity	Not applicable to routine hypertension or angina use
Generic competition	Established across multiple strengths and manufacturers

Generic entry is therefore possible where the applicant meets the relevant bioequivalence and labeling requirements and addresses any listed patents through certification. The precise launch date depends on the ANDA's approval status, patent certifications, 180-day exclusivity and litigation outcome.

What is the Orange Book status of diltiazem extended-release products?

The Orange Book identifies reference listed drugs, approved generic equivalents and, where applicable, patents and exclusivity information. Diltiazem extended-release entries are product-specific and should not be treated as interchangeable across all formulations.

Important distinctions include:

• Extended-release capsules versus extended-release tablets.
• Different reference listed drugs.
• Different strengths.
• Different release mechanisms.
• Therapeutic equivalence codes assigned to individual products.
• Labeling differences affecting administration and substitution.

A generic capsule equivalent to one reference product is not automatically equivalent to a tablet-based product or to another capsule reference with a different release system. Orange Book status should be evaluated at the application, dosage-form, strength and reference-product level.[2]

Which companies are challenging diltiazem extended-release products?

The market has historically included major generic manufacturers such as Actavis, Teva, Mylan, Sandoz, Lupin and other FDA-approved suppliers, along with branded or authorized-generic channels. The competitive field changes by strength, dosage form and manufacturing site.

The main competitive groups are:

1. Large generic companies with established modified-release manufacturing.
2. Contract manufacturers supplying smaller label owners.
3. Brand-linked authorized-generic suppliers.
4. Specialty manufacturers pursuing differentiated capsules or tablets.
5. Regional suppliers competing on shortages and hospital-channel supply.

Public patent-litigation risk is generally lower for a mature diltiazem product than for a newly launched protected medicine. The material risks are product-specific Paragraph IV certifications, ANDA approval timing, therapeutic-equivalence status and manufacturing continuity.

What Paragraph IV challenges affect diltiazem extended-release?

A Paragraph IV certification states that a listed patent is invalid, unenforceable or will not be infringed by the proposed generic product. For diltiazem extended-release, the relevant issue is usually whether a formulation or method-of-use patent remains listed against the specific reference product.

A generic sponsor considering Paragraph IV entry should evaluate:

• Whether the patent is listed for the exact reference product.
• Whether the claims cover the proposed polymer system or release profile.
• Whether the ANDA contains a non-infringement position.
• Whether a notice letter would trigger litigation.
• Whether a 30-month stay could delay approval.
• Whether 180-day generic exclusivity is available.
• Whether the commercial value justifies litigation costs.

Because the active ingredient is old and multiple products compete, a Paragraph IV strategy is most attractive when the targeted product has meaningful sales and limited substitutable supply. It is less attractive when several approved generic alternatives already exist.

How strong is the patent estate for diltiazem extended-release?

The patent estate is likely weak at the active-ingredient level and potentially moderate at the dosage-form level. Its strength depends on whether a sponsor has a live, enforceable patent that covers the commercial product rather than a broad historical formulation concept.

Patent factor	Assessment
Compound patent position	Weak or expired
Basic therapeutic use	Weak for ordinary hypertension and angina
Multiparticulate formulation	Potentially relevant if claims remain live
Matrix formulation	Potentially relevant but vulnerable to design-around
Manufacturing process	Moderate if process-specific and difficult to avoid
Sprinkle administration	Potentially valuable if linked to a defined dosage form
Method-of-use claims	Limited value unless narrowly differentiated
Freedom to operate	Requires product-specific claim mapping

Design-around options are extensive. A sponsor can change polymer type, coating architecture, pellet size, matrix composition, capsule fill, manufacturing sequence or release mechanism. This generally reduces the blocking power of a single formulation patent unless the claims cover broad functional parameters that are difficult to avoid.

What manufacturing and IP barriers affect commercial entry?

Manufacturing is a more important barrier than active-ingredient IP for most diltiazem extended-release opportunities.

Multiparticulate manufacturing barriers

Key process risks include:

• Uneven drug layering.
• Nonuniform coating thickness.
• Pellet breakage during handling.
• Electrostatic charging.
• Agglomeration during curing.
• Capsule fill-weight variability.
• Dissolution drift after scale-up.

A sponsor needs process analytical controls for pellet size, coating weight gain, moisture, assay, content uniformity and dissolution.

Matrix-tablet manufacturing barriers

Matrix products face different risks:

• Granulation variability.
• Compression-induced changes in porosity.
• Tablet-to-tablet weight and hardness variation.
• Lubricant overmixing.
• Sticking and picking.
• Sensitivity to storage humidity.
• Release changes after packaging transitions.

The manufacturing route should be selected with commercial scale in mind. A formulation that performs well at laboratory scale but requires slow coating, extensive manual handling or narrow process windows may not support competitive pricing.

What FDA regulatory pathway applies to a new formulation?

An applicant seeking a generic version of an existing extended-release product would generally use an ANDA. The application must demonstrate pharmaceutical equivalence and bioequivalence to the selected reference listed drug.

A materially different release mechanism, new dosage form, new indication or clinically meaningful administration attribute may require a 505(b)(2) application. That route can support differentiated formulation claims but normally carries higher development and regulatory costs.

FDA evaluation typically includes:

• Comparative dissolution in multiple media.
• Fasting pharmacokinetic studies.
• Fed pharmacokinetic studies.
• Assessment of food effect.
• Strength bridging.
• Stability data.
• Alcohol-induced dose-dumping assessment where relevant.
• Labeling review.
• Manufacturing-process validation.

For modified-release products, dissolution is a critical quality attribute and may be a stronger predictor of regulatory risk than simple assay or content uniformity.[3]

What commercial opportunities exist for diltiazem extended-release?

Sprinkle capsules

A sprinkle product can address patients who cannot swallow intact capsules. The commercial value is highest when the beads maintain release performance after capsule opening and administration with a compatible soft food.

The product must control:

• Bead recovery from the capsule.
• Resistance to crushing or chewing.
• Food compatibility.
• Dose uniformity after sprinkling.
• Labeling instructions.
• Stability after temporary exposure to moisture.

Low-cost generic substitution

A reliable, low-cost product can compete where the market has multiple label owners but intermittent supply. The opportunity depends on manufacturing cost, FDA approval status and pharmacy substitution.

Strength and pack rationalization

A manufacturer can improve inventory efficiency by focusing on high-volume strengths, usually 120, 180, 240 and 300 or 360 mg depending on the target product. A smaller strength portfolio reduces tooling, validation and inventory costs but may limit formulary coverage.

Reduced food effect

A formulation with lower fed-versus-fasted variability can be commercially attractive, but the claim must be supported by comparative pharmacokinetic data. A lower food effect may also reduce prescribing friction and improve adherence.

Hospital and institutional supply

Extended-release diltiazem is less central to acute hospital dosing than immediate-release or intravenous diltiazem, but institutional purchasers may value dependable supply, standardized strengths and unit-dose packaging.

International markets

Geographic opportunities exist in markets where extended-release cardiovascular products remain branded, under-supplied or less developed. Regulatory requirements differ by jurisdiction, particularly for bioequivalence, modified-release testing, excipient acceptability and therapeutic substitution.

How does diltiazem extended-release compare with competing calcium-channel blockers?

Diltiazem competes with amlodipine, felodipine, verapamil and other antihypertensive products. Amlodipine has a longer effective half-life and simpler immediate-release tablet design, which reduces formulation complexity. Verapamil competes in overlapping cardiovascular indications but has its own extended-release technologies and dose forms.

Product characteristic	Diltiazem ER	Amlodipine	Verapamil ER
Release challenge	Moderate to high	Lower for standard tablets	Moderate to high
Main differentiation	Once-daily exposure and cardiac rate effects	Long half-life and simple dosing	Cardiac and antihypertensive use
Formulation complexity	Capsules and tablets	Usually lower	Often high
Generic competition	Mature	Very mature	Mature
Excipient opportunity	Stronger for release engineering	Limited for basic products	Strong for delivery systems
Key clinical constraint	Bradycardia, conduction effects, CYP3A4 interactions	Edema and reflex effects	Bradycardia, constipation, conduction effects

Diltiazem's formulation opportunity is greater than its molecule-level opportunity because the product still requires controlled delivery to manage exposure and dosing frequency.

Key Takeaways

• Diltiazem hydrochloride extended-release is a mature generic market with expired compound exclusivity.
• Commercial differentiation depends on release technology, food-effect control, sprinkle administration, supply reliability and cost.
• Multiparticulate capsules provide the strongest platform for dose flexibility and sprinkle products.
• Matrix tablets offer lower manufacturing cost but require tight control of polymer grade, porosity and compression.
• Product-specific Orange Book analysis is essential because capsules and tablets may reference different listed drugs.
• Paragraph IV opportunities depend on live formulation or method-of-use patents and the sales value of the targeted reference product.
• Manufacturing consistency, dissolution matching and scale-up are usually greater barriers than active-ingredient IP.
• A new ANDA is most practical for a product that closely matches an approved reference listed drug.
• A 505(b)(2) strategy is more appropriate for a materially differentiated release profile, dosage form or administration method.
• The strongest commercial concept is a once-daily, sprinkle-capable, alcohol-resistant multiparticulate capsule with competitive manufacturing economics.

FAQs on diltiazem hydrochloride extended-release excipients and market entry

Which polymer is most suitable for diltiazem extended-release pellets?

Ethylcellulose and acrylic methacrylate copolymers are common starting points for insoluble or pH-independent coating systems. The final selection depends on dissolution matching, food effect, alcohol resistance, stability and regulatory acceptability.

Can diltiazem extended-release capsules be opened and sprinkled?

Only products specifically labeled for that administration method should be opened and sprinkled. Crushing or chewing extended-release beads can alter exposure and compromise controlled release.

Is a diltiazem matrix tablet easier to approve than a coated-pellet capsule?

Not necessarily. Matrix tablets are often easier to manufacture, but approval depends on reference-product matching, pharmacokinetics and dissolution. A capsule may be the lower-risk regulatory design when the reference product is also a multiparticulate capsule.

Does diltiazem extended-release require a food-effect study?

Modified-release products generally require evaluation under fasting and fed conditions. The study design and acceptance criteria depend on the reference listed drug and applicable FDA requirements.[3]

What is the most defensible IP strategy for a new diltiazem extended-release product?

A sponsor should focus on claims directed to a specific release architecture, manufacturing process, stability profile or clinically supported administration method. Broad claims covering conventional diltiazem extended-release concepts are more vulnerable to prior-art and design-around challenges.

References

1. U.S. Food and Drug Administration. (2024). Diltiazem hydrochloride extended-release capsules: Prescribing information. DailyMed.

2. U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations. FDA Orange Book.

3. U.S. Food and Drug Administration. (1997). Extended release solid oral dosage forms: Development, evaluation, and application of in vitro/in vivo correlations. Guidance for Industry.

4. U.S. Food and Drug Administration. (2002). Food-effect bioavailability and fed bioequivalence studies. Guidance for Industry.

5. National Library of Medicine. (2024). Diltiazem hydrochloride drug labeling and inactive ingredient information. DailyMed.