The success of a pharmaceutical product hinges not only on the active ingredient, but also on how that ingredient is formulated. Strategic formulation decisions can dramatically influence both drug product stability, how well it maintains its integrity over time, and bioavailability, or how efficiently it’s absorbed by the body.
Key Takeaways
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- Formulation design plays a crucial role in ensuring the drug remains chemically and physically stable over time and the drug product provides a consistent therapeutic effect.
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- Poor formulation choices can lead to reduced shelf life, poor absorption, or treatment failure.
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- Factors like solubility, excipient selection, and dosage form all impact drug product stability and bioavailability.
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- Pharmaceutical companies must conduct robust preformulation and formulation studies to optimise outcomes.
Why Formulation Matters in Drug Development
Formulation development is more than mixing ingredients – it’s a critical phase in drug development that ensures your drug product is safe, stable, and effective. During the development phase, formulation scientists make key decisions about excipients, delivery methods, and dosage forms that directly impact how a drug behaves in the body and on storage.
Poorly designed formulation studies can result in:
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- Degradation of the active pharmaceutical ingredient (API) over time
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- Unpredictable release and dissolution profiles that affect therapeutic outcomes
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- Inconsistent bioavailability, especially in poorly soluble drugs
By contrast, a well-formulated product ensures consistent performance and supports a successful regulatory submission.
Factors That Influence Drug Stability
Drug stability refers to how well a pharmaceutical product maintains its quality and safety over time under various environmental conditions. Several formulation variables can influence this, including:
1. Excipient Compatibility
Excipients must not interact with the API. Compatibility studies identify potential reactivity that could lead to degradation.
2. Dosage Form Selection
The intended route of administration and physicochemical properties of the drug facilitates the selection of the most appropriate dosage form (eg. tablets, suspension, creams)
3. pH and Buffer Systems
Many drugs are pH-sensitive. Formulators can use buffering agents to maintain an optimal pH and improve product solubility and stability.
4. Polymorphism
Different crystalline forms of the same API can have varying stability and solubility characteristics. Controlling polymorphic forms is critical to minimize impact on bioavailability and stability of the drug product.
5. Packaging
Primary packaging, such as blister packs or glass vials, is often chosen based on how it protects the formulation from environmental factors (such as light, moisture, heat and oxygen) and chemical interaction with the packaging.
The Role of Formulation in Enhancing Bioavailability
Bioavailability refers to the extent and rate at which the API reaches systemic circulation. Many promising drug candidates fail in development due to poor solubility or permeability—issues that can often be addressed at the formulation stage.
Key formulation techniques to improve bioavailability include:
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- Particle size reduction (micronisation or nanonisation)
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- Use of surfactants or solubilising agents
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- Salt formation to enhance solubility
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- Lipid-based delivery (eg. nanoemulsions, liposomes)
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- Solid dispersions or amorphous formulations
Understanding the Biopharmaceutics Classification System (BCS) helps guide the formulation strategy, especially for BCS Class II and IV compounds where solubility and permeability are challenging.
Integrating Stability and Bioavailability into a Formulation Strategy
Optimising both stability and bioavailability is a delicate balancing act. For instance, a formulation that improves solubility might introduce new stability issues. This is why preformulation studies are essential—they help predict how various formulation approaches will perform under real-time and accelerated conditions.
Best practices include:
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- Characterising the API by evaluating solubility, physical and chemical stability, and identification of degradation pathways
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- Designing drug product with ICH stability guidelines in mind
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- Validating analytical methods to monitor degradation and performance
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- Using Quality by Design (QbD) principles to ensure reproducibility and regulatory compliance
PharmSky’s Approach to Formulation and Analytical Support
At PharmSky, we support pharmaceutical clients by developing formulations that optimise both stability and bioavailability, while remaining compliant with global regulatory expectations. Our integrated services include:
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- Pharmaceutical formulation development for oral and parenteral dosage forms
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- Stability testing under ICH conditions
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- Excipient screening and compatibility studies
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- Bioavailability-enhancing formulation strategies
We collaborate closely with clients across preclinical, clinical, and commercial stages to ensure formulation choices align with their development goals and timelines. For tailored support in improving drug stability or enhancing bioavailability, contact the PharmSky team to discuss your development goals.
