Intranasal Drug Delivery Development: Engineering Reliable Nasal Spray Products

Introduction: Nasal Delivery – A Route with Untapped Potential

 

For a route that is easy to use, fast-acting, and non-invasive, intranasal drug delivery is still surprisingly underutilized in modern drug development.

 

At a time when patients and providers are both looking for simpler, faster, and more effective treatment options, nasal spray drug products offer a compelling alternative to traditional oral and injectable routes. It combines convenience with pharmacokinetic advantages that are difficult to achieve elsewhere.

From a clinical and patient standpoint, intranasal drug delivery enables:

• Rapid absorption through the highly vascular nasal mucosa

• Fast onset of action, particularly in acute settings

• Avoidance of hepatic first-pass metabolism

• Improved patient compliance due to ease of administration

 

Despite these advantages, the route has historically been associated with localized therapies, primarily for conditions such as rhinitis, sinusitis, and nasal congestion. As a result, its broader potential has often been overlooked.

 

However, this perception is beginning to shift. Increasingly, intranasal drug delivery is being explored for systemic applications, including therapies where rapid absorption or bypassing biological barriers is critical. Its ability to enable drug entry into the systemic circulation, and, in some cases, to support CNS-targeted delivery, positions it as a versatile platform rather than a niche option.

 

How is perception changing?

 

What is becoming clear is that intranasal drug delivery is not limited by its biology, but by how it is perceived and developed.

 

Developing a reliable nasal product, however, is inherently multidisciplinary. It requires close alignment across:

• Formulation design

• Device performance

• Analytical characterization

• Regulatory expectations

 

Unlike conventional dosage forms, where these elements can often be optimized independently, intranasal drug delivery demands that they be developed in parallel to ensure consistent dosing and performance.

 

Here, we explore the scientific and development considerations that shape successful nasal spray products and what it takes to fully realize the potential of intranasal drug delivery.

 

Understanding the Nasal Environment

 

Why Biology Shapes Formulation Strategy

 

The effectiveness of intranasal drug delivery depends on how well a formulation performs within the constraints of the nasal environment. Unlike oral routes, nasal drug absorption occurs in a limited and highly variable biological setting.

 

The nasal cavity consists of distinct regions — the nasal vestibule, atrium, respiratory region, olfactory region, and nasopharynx — each with different permeability and functional roles in nasal drug absorption.

 

Several factors directly influence nasal drug absorption:

• Epithelial permeability

• Enzymatic activity in the nasal mucosa

• Blood flow and neuronal regulation

• Nasal secretions (pH, viscosity, composition)

 

A key constraint is the limited absorption surface area, which also varies across patients, making consistent absorption challenging.

 

“The area available for nasal administration is relatively small and varies across patients, which affects drug absorption,” he continues.

In addition, mucociliary clearance (MCC) removes substances from the nasal cavity within ~20 minutes, further restricting the window for nasal drug absorption.

 

As a result, successful intranasal drug delivery must account for limited residence time, physiological variability, and disease-related changes, ensuring that formulations are designed to work with the nasal environment — not against it.

 

Designing the Nasal Spray Formulation

 

Effective intranasal drug delivery begins with a well-designed nasal spray formulation, where both composition and performance must be carefully aligned.

 

Nasal spray drug products typically consist of drug substances dissolved or suspended in aqueous systems, delivered through a metered spray device to ensure reproducible dosing.

 

Core components of nasal spray formulation play specific functional roles:

• Buffers maintain physiological pH.

• Solubilizers enhance drug solubility.

• Preservatives prevent microbial contamination.

• Antioxidants protect against chemical degradation.

• Humectants maintain mucosal hydration.

• Surfactants improve stability and membrane permeability.

• Mucoadhesive polymers increase residence time on the nasal mucosa.

 

A key decision in intranasal formulation development is whether to design a solution or suspension spray. Solution formulations offer uniformity and ease of dosing, while suspension systems are often required for poorly soluble drugs, introducing additional complexity around particle size and dispersion.

 

To enhance nasal drug absorption, formulations may also incorporate permeation enhancers or absorption-modifying excipients, although their impact on safety and nasal tolerability must be carefully evaluated.

 

Critical parameters that define the performance of a nasal spray formulation include:

• pH (aligned with nasal physiology)

• Osmolality

• Viscosity (impacting residence time and clearance)

• Drug solubility

• Particle dispersion characteristics

 

Ultimately, successful intranasal formulation development requires balancing three interdependent factors

• Drug stability
• Absorption efficiency
• Nasal tolerability

 

Achieving this balance is central to ensuring that intranasal drug delivery systems are both effective and patient-friendly.

 

Drug–Device Combination Challenges

 

Nasal sprays are drug device combination products, which means performance depends not just on what's inside the bottle, but how it is delivered.

 

In intranasal drug delivery, the device plays a central role in ensuring the drug reaches the right part of the nasal cavity, in the right amount, every time.

 

Key components of the device include:

• Spray pump mechanism

• Actuator

• Nozzle design

• Metering chamber

 

These directly influence:

• How much dose is delivered

• How the spray spreads (plume)

• The size of droplets generated

 

Together, these factors shape how consistently the product performs.

 

“The drug–device combination is always a challenge. Even if the formulation is optimized, the way the device delivers the dose can vary,” comments Sudarshan.

There's also a practical layer to this — how patients actually use the device. Small variations in use can impact dosing, such as:

• How long the spray is actuated

• How deeply the nozzle is inserted

• The angle of administration

 

This makes intranasal drug delivery different from many other dosage forms. It's not enough to get the formulation right; the delivery system has to work just as reliably in the patient's hands.

 

That's why the successful development of drug-device combination products depends on designing the formulation and the device together, not separately.

 

Critical Quality Attributes in Nasal Spray Development

 

Consistent performance in intranasal drug delivery depends on how well key attributes are controlled during nasal spray characterization. These parameters ensure that every spray delivers the intended dose, in the intended way.

 

Core attributes include:

• pH : Formulations are typically aligned with nasal physiology (~5.0–6.5) to support tolerability and stability.

• Osmolality : Influences both drug permeability and patient comfort, making it an important design consideration.

• Viscosity : Affects how long the formulation stays in the nasal cavity, while also influencing mucociliary clearance.

• Spray Content Uniformity (SCU) : Ensures consistent drug delivery across sprays, containers, and batches.

• Droplet Size Distribution : A key determinant of deposition, with typical droplet sizes ranging from 30–120 µm.

• Spray Pattern and Plume Geometry : Used to confirm that the device delivers a consistent and reproducible spray profile.

• Particle Size Distribution : Particularly relevant for suspension formulations, where particle behavior can impact delivery and stability.

 

Additional performance-linked parameters also play a role in nasal spray characterization, including:

• Shot weight, which reflects dose consistency per actuation.

• Pump reproducibility, ensuring uniform delivery across units.

• Actuation force, which can influence real-world usability and dosing consistency.

 

Together, these attributes provide a complete picture of how reliably a nasal spray performs, ensuring that intranasal drug delivery systems deliver consistent dosing, predictable deposition, and reproducible device performance.

 

In Vitro Testing of Nasal Spray Products

 

In vitro nasal spray testing is central to demonstrating that intranasal drug delivery systems perform consistently and as intended. Because these are drug-device combination products, testing must evaluate both formulation and device together.

 

At a high level, nasal spray analytical methods are used to confirm:

• Delivered dose consistency per actuation.

• Spray pattern and plume geometry for reproducible spray formation.

• Droplet size distribution, which impacts nasal deposition.

• Particle size distribution (for suspensions) to ensure uniform dosing.

 

These in vitro assessments provide an early, controlled way to ensure that the product will deliver the right dose, in the right form, to the right location, before moving into further stages of development.

 

Stability and Compatibility Considerations

 

In intranasal drug delivery, stability is closely linked to how the product performs over time. Even small changes during storage can influence dose delivery through the device.

 

Nasal spray stability testing typically evaluates:

• Chemical degradation.

• Changes in viscosity.

• Color or appearance shifts.

• Microbial growth.

 

“Stability is critical because changes in viscosity or appearance during storage can affect how the dose is delivered through the device,” he says.

The role of the container closure system, including the bottle, pump, and actuator, is also important. These components are in continuous contact with the formulation and can influence product quality over time.

 

This is where extractables and leachables in nasal sprays need careful evaluation. Materials from pump components or packaging may migrate into the formulation, potentially affecting safety and performance.

“Because nasal products may enter systemic circulation directly, extractables and leachables from the container system must be carefully monitored,” he continues.

For intranasal drug delivery, stability and compatibility are assessed together to ensure consistent dosing and product quality throughout shelf life.

 

Manufacturing Considerations in Nasal Spray Development

 

Translating intranasal drug delivery from development to commercial scale requires tight control across formulation, device, and packaging.

 

In nasal drug product manufacturing, consistency depends on how well these elements are brought together during production. This includes both the formulation process and the integration of the delivery device.

 

Key considerations in nasal spray manufacturing include:

• Formulation preparation, ensuring consistent pH, viscosity, and drug dispersion.

• Nasal spray fill finish, where accurate filling supports dose uniformity across units.

• Container and closure systems, which must maintain product integrity and performance.

• Pump and actuator assembly, directly influencing spray characteristics and delivery.

• Quality control testing, confirming consistent formulation and device performance.

 

Because performance is closely tied to both formulation and device, early alignment between development teams, device suppliers, and manufacturing specialists helps reduce scale-up risks and supports smoother commercialization of intranasal drug delivery products.

 

Regulatory Expectations for Nasal Spray Products

 

Regulatory agencies classify intranasal drug delivery products as complex drug-device combinations, with a strong emphasis on demonstrating equivalence in both formulation and performance.

 

For generics, development programs typically focus on:

• Q1/Q2 formulation equivalence.

• Comparable spray pattern and plume geometry.

• Equivalent droplet size distribution.

• Similar viscosity and suspension characteristics.

Given this, analytical characterization and device testing are central to regulatory approval, particularly for demonstrating consistent dose delivery and performance.

 

Regulatory expectations for intranasal drug delivery are further guided by established frameworks such as:

• FDA nasal spray guidance.

• EMA nasal product guidance.

• The FDA complex generics program, which outlines expectations for demonstrating equivalence in complex drug–device products.

• Together, these requirements reinforce the need for a well-integrated approach in which formulation, device, and analytical data collectively support approval.

 

Emerging Opportunities in Intranasal Drug Delivery

 

The scope of intranasal drug delivery is expanding well beyond traditional allergy and congestion treatments. Increasingly, it is being explored across a wider range of therapeutic areas, including:

 

 

These approaches are designed to address core challenges, improving drug absorption, enhancing stability, and making products easier for patients to use.

 

A key area of interest is nose-to-brain drug delivery, where the nasal route offers a pathway to bypass the blood–brain barrier and enable more direct access to the central nervous system. This has opened up possibilities for CNS-active therapies and more targeted treatment approaches.

 

There is also growing interest in intranasal biologics, including peptides and other complex molecules, where the nasal route can help avoid degradation associated with gastrointestinal delivery.

 

On the formulation side, several advances are shaping the next phase of intranasal drug delivery, such as:

 

 

Conclusion

 

De-Risking Nasal Spray Development with the Right CDMO Partner

 

Successful intranasal drug delivery depends on how well formulation, device, analytics, and regulatory strategy come together — early and consistently.

Each stage brings its own challenges, from dose reproducibility to stability and regulatory alignment. Managing these in isolation increases risk; integrating them reduces it.

Experienced CDMO partners like Strides Pharma support this integration by:

• Aligning formulation and device performance from the outset.

• Designing fit-for-purpose analytical and characterization strategies.

• Addressing stability, compatibility, and regulatory requirements.

• Enabling efficient scale-up and manufacturing readiness.

 

“With the right partner, that complexity becomes manageable, turning development risk into a clear path to market.”

 

FAQs

 

Q. What makes nasal spray drug product development more complex than other dosage forms?

Intranasal drug delivery involves both a formulation and a device working together. Performance depends on how well dose delivery, spray characteristics, and patient use align, making it more interdependent than conventional dosage forms.

 

Q. What are the key challenges in nasal spray formulation development?

Balancing drug stability, absorption, and nasal tolerability within a limited absorption window. Factors such as pH, viscosity, solubility, and excipient selection all directly impact performance.

 

Q. What are the most critical formulation parameters to control in nasal spray formulations?

pH, osmolality, viscosity, drug solubility, and particle or droplet characteristics are central to ensuring consistent intranasal drug delivery.

 

Q. What factors influence nasal drug absorption?

Nasal drug absorption is influenced by epithelial permeability, enzymatic activity, blood flow, nasal secretions, mucociliary clearance, and patient-specific variability.

 

Q. Why is droplet size distribution such an important parameter in nasal spray performance?

Droplet size determines where the drug deposits. Larger droplets may remain in the anterior nose, while very small droplets risk being inhaled, making controlled distribution critical for effective intranasal drug delivery.

 

Q. How is droplet size measured in nasal spray products?

Droplet size distribution is typically measured using techniques such as laser diffraction, reported as parameters like D10, D50, and D90 to characterize the spray profile.

 

Q. How does the delivery device influence dose consistency and drug deposition in the nasal cavity?

Device design, including the pump, nozzle, and actuator, controls emitted dose, spray pattern, and plume geometry, all of which impact deposition and consistency.

 

Q. What analytical tests are required to characterize nasal spray performance?

Key tests include spray content uniformity, droplet size distribution, spray pattern, plume geometry, particle size (for suspensions), and pump performance.

 

Q. What regulatory tests are required for nasal spray drug products?

Regulatory expectations typically include demonstrating formulation equivalence, device performance (spray pattern, droplet size), dose uniformity, and stability through validated analytical testing.

 

Q. What stability challenges are unique to nasal spray drug products?

Changes in viscosity, appearance, or microbial growth can affect how the formulation is delivered through the device. Compatibility with the container-closure system and with extractables and leachables in nasal sprays are also key considerations.

 

Q. At what stage of development should device selection be integrated into formulation design?

Device selection should begin early in development. In intranasal drug delivery, formulation and device need to be optimized together to ensure consistent performance in real-world use.

 

Key Takeaways

 

• Intranasal drug delivery offers a fast, non-invasive route with clear advantages in absorption and patient convenience.

• Successful development depends on aligning formulation science with the biological constraints of the nasal environment.

• Device performance plays a critical role in ensuring consistent dose delivery and deposition.

• Stability, analytical characterization, and regulatory alignment are central to building reliable nasal spray products.

• With integrated expertise across development and manufacturing, partners like Strides can help simplify complexity and accelerate intranasal drug delivery to market.

 

References

 

• Hanson LR, Frey WH 2nd. Intranasal delivery bypasses the blood-brain barrier to target therapeutic agents to the central nervous system and treat neurodegenerative disease. BMC Neurosci. 2008;9 Suppl 3(Suppl 3):S5.

• Nasal Spray and Inhalation Solution, Suspension, and Spray Drug Products – Chemistry, Manufacturing, and Controls Documentation. https://www.fda.gov/media/70857/download

• FDA Complex Generics Program. https://www.fda.gov/drugs/generic-drugs/complex-generics

• Guideline on the Pharmaceutical Quality of Inhalation and Nasal Products. https://www.ema.europa.eu/en/documents/scientific-guideline/guideline-pharmaceutical-quality-inhalation-nasal-products_en.pdf

• Wu X, Zang R, Qiu Y, et al. Intranasal Drug Delivery Technology in the Treatment of Central Nervous System Diseases: Challenges, Advances, and Future Research Directions. Pharmaceutics. 2025;17(6):775.

• Crowe TP, Hsu WH. Evaluation of Recent Intranasal Drug Delivery Systems to the Central Nervous System. Pharmaceutics. 2022;14(3):629.