4. Emulsion Dosage Form.pdf

Emulsion Dosage Form : Manufacturing and Quality Control SHAHIRAH YASIN  INTRODUCTION Emulsion dosage form – type of pharmaceutical formulation composed of 2 immiscible liquids, typically oil and water, stabilized by emulsifying agent. Emulsion are colloidal system where...

Emulsion Dosage Form : Manufacturing and Quality Control SHAHIRAH YASIN  INTRODUCTION Emulsion dosage form – type of pharmaceutical formulation composed of 2 immiscible liquids, typically oil and water, stabilized by emulsifying agent. Emulsion are colloidal system where one liquid (dispersed phase) is dispersed in the form of small droplets within the other liquid (continuous phase). The emulsifying agent often a surfactant helps prevent coalescence and provides stability to the emulsion, allowing it to remain in a dispersed state and maintain the stability of the emulsion Importance of Emulsion in Pharmaceuticals Versatility – can be tailored to accommodate a wide range of drugs, both hydrophilic and lipophilic Flexibility in drug delivery – adapted for different routes of administration (oral, topical, intravenous) Improved drug stability – protect drug from degradation and improved chemical stability Enhanced bioavailability – increase drug absorption and bioavailability, leading to improved therapeutic outcome Localized drug delivery – allow targeted drug delivery to specific sites Formulation of combination products – facilitate the combination of incompatible drugs in a single dosage form Classification Classification Based on nature Based on of dispersed globule size phase Oil-in-water Water-in-oil Micro emulsion Fine emulsion (o/w) (w/o) (0.01um) (0.25 – 25 um)  Water-in-oil (w/o) emulsion Water droplets are dispersed in an oil continuous phase. The water droplets are surrounded by the emulsifying agent, which has its hydrophilic (water-loving) part oriented towards the water droplets and its lipophilic (oil-loving) part oriented towards the oil phase. This type of emulsion if often used when the drug is hydrophilic, and a slower release is desired. Eg: Cold Cream Used in skincare. It typically consists of water droplets dispersed in an oil continuous phase, along with emulsifier and other skin-nourishing ingredients. Cold creams are used to moisturize and protect the skin, and they are particularly suitable for dry and sensitive skin types  Oil-in-water (o/w) emulsion Oil droplets are dispersed in a water continuous phase The oil droplets are surrounded by the emulsifying agent, with its hydrophilic part oriented towards the continuous water phase and its lipophilic part oriented towards the oil droplets. This type of emulsion is commonly used for drugs that are lipophilic and require rapid release and absorption Eg: Milk In milk, fat droplets are dispersed in a continuous phase of water, along with other components like proteins, lactose and minerals. The emulsifying agents in milk, such as phospholipid and proteins, help stabilize the emulsion and prevent separation of fat Emulsifying agents Emulsifying agent is also known as surfactant – essential components in emulsion formulations. They have a unique structure with both hydrophilic and lipophilic groups. The surfactant molecules align at the interface between the oil and water phases, reducing the surface tension and preventing the droplets from coalescing Eg of emulsifying agents Tweens (Polysorbates) Spans (Sorbitan fatty acid esters) Sodium lauryl sulfate (SLS) Cetyltrimethylammonium bromide (CTAB) Lecithin ✓HLB Concept ✓Hydrophilic-Lipophilic Balance ✓Numerical scale ranging from 1-20 that quantifies the hydrophilic and lipophilic properties of a surfactant ✓HLB value indicates how much a surfactant prefers to be in the water phase (higher HLB) or the oil phase (lower HLB) ✓The selection of an appropriate surfactant with the right HLB value is crucial in formulating emulsion with desired properties ✓Surfactant with low HLB (10) are more hydrophilic and are suitable for oil-in-water emulsions ✓The HLB concept helps formulators choose the right combination of emulsifier to achieve stable emulsions with the desired characteristics for a specific pharmaceutical application Composition Co- Oil Phase emulsifier Emulsifying Water agent Phase Oil phase Aqueous Phase Emulsifying Co –emulsifiers Non polar liquid Polar liquid agents Used in conjunction Constitutes the Form continuous (surfactant) with emulsifying dispersed phase in phase emulsion agent to improve Molecule with both stability and the emulsion It can be water or hydrophilic and Composed of water-based consistency of the lipophilic regions emulsion various oils, or solutions To stabilize the oil lipids, depending They enhance the and water phases, emulsification on the specific drug preventing from and formulation process and separating and contribute to the requirements forming droplets formation of a stable system  Selection of oils and surfactant Choose an oil phase that can solubilize the drug effectively, especially for Drug solubility lipophilic drug Water soluble drugs are better suited for emulsion with an oil-in-water type Sustained release – w/o emulsion preferred Drug release profile Rapid release – o/w- emulsion Some drugs may degrade or react in the presence of specific oils or surfactants Drug stability Select components that ensure drug stability throughout the shelf life of the emulsion Consider the route of administration and target site action Target site Certain oil and surfactants are better suited for topical formulations, while other may be more appropriate for oral or parenteral administration  Emulsification Technique Emulsification – process of dispersing one immiscible liquid phase into another with the help of emulsifying agent Homogenization (https://www.youtube.com/watch?v=Ed0K5Cjbmr0) High-pressure homogenization is a widely used method that involves forcing the emulsion through a small nozzle or valve under high pressure This process breaks down the large droplets into smaller, more uniform droplets, resulting in stable emulsion Phase Inversion temperature (PIT) (https://www.youtube.com/watch?v=YbfsNEtCFPw) The emulsion is prepared at a specific temperature where the emulsifier exhibits a transition from water water-in-oil to oil-in-water or vice versa By adjusting the temperature, the emulsion type can be controlled  Ultrasonication (https://www.youtube.com/watch?v=UU1RJVzEoww) Involves the application of high-frequency sound waves, which create cavitation and shear forces, breaking down large droplets and promoting emulsification Micro fluidization (https://www.youtube.com/watch?v=VnvT2AlGycs) Technique that utilizes high-pressure pumps to force the emulsion through small channels or chambers. This process provides efficient and uniform droplet size reduction Equipment used in manufacturing emulsions Homogenizer High-pressure homogenizers, such as piston-gap homogenizers or high-shear homogenizers, are commonly used for emulsion preparation. They provide the necessary shear forces to reduce droplet size and create stable emulsions. Microfluidizer Microfluidizers are specialized equipment used for micro fluidization. They use high-pressure pumps and interaction chambers to achieve uniform droplet size reduction. Stirrers and mixers Conventional emulsions can be prepared using stirrers or mixers, which are suitable for small-scale and simple emulsions. Phase Inversion Temperature (PIT) PIT apparatus is used to prepare emulsions with controlled phase inversion by adjusting the temperature during emulsification.  Key consideration during emulsion manufacturing process Emulsifier selection: Choosing the right emulsifier(s) and co-emulsifiers is critical to achieving stability and ensuring compatibility with the drug and other excipients. Phase order and rate of addition: Proper sequence and rate of addition of components (oil, water, emulsifiers) can impact the quality and stability of the emulsion. Shear rate and time: The intensity and duration of shear forces during emulsification affect droplet size and stability. Optimizing these parameters is crucial for obtaining the desired emulsion characteristics. Temperature control: Temperature can influence emulsion stability and phase inversion. Maintaining the appropriate temperature during the process is essential.  Hygiene and contamination control: Ensuring a clean and sterile manufacturing environment is vital to prevent contamination and extend shelf life. Quality control: Regular quality checks during and after emulsion preparation, such as droplet size analysis, pH measurement, and stability testing, are essential to ensure the consistency and quality of the final product. Scale-up considerations: If the emulsion is intended for commercial production, scalability should be taken into account during the development process to ensure reproducibility.  Factors affecting emulsion stability ❑ Emulsifier concentration: The concentration of emulsifier(s) in the formulation affects the stability of the emulsion. Insufficient emulsifier may lead to coalescence and phase separation, while excessive emulsifier may cause flocculation or Ostwald ripening. ❑ Droplet size: Smaller droplet size generally contributes to improved stability. Larger droplets are more likely to coalesce and separate over time. ❑ Emulsification technique: The method used to prepare the emulsion can influence its stability. High-pressure homogenization and microfluidization generally result in smaller and more uniform droplets, leading to enhanced stability compared to conventional methods. ❑ Temperature: Emulsions may be affected by temperature changes. Some emulsions may exhibit phase separation or instability at extreme temperatures. ❑pH: The pH of the emulsion can impact the charge and solubility of the emulsifiers, affecting the stability of the system. ❑Ionic strength: Changes in ionic strength can influence the stability of emulsions, especially for emulsifiers with charged groups. ❑Presence of electrolytes: Electrolytes can disrupt the stabilization of emulsions by affecting the emulsifier's interfacial properties. ❑Oil phase composition: The choice of oil or lipid used in the formulation can influence emulsion stability, as some oils may interact differently with the emulsifiers.  Stability Testing Freese-thaw Centrifugation Heat stability cycles Particle size Visual analysis inspection 1.Centrifugation: Emulsions are subjected to centrifugal forces to assess their resistance to phase separation or creaming. 2.Freeze-thaw cycles: Emulsions are subjected to multiple freeze-thaw cycles to assess their stability under temperature fluctuations. 3.Heat stability: Emulsions are exposed to elevated temperatures to evaluate their stability under heat stress. 4.Particle size analysis: Measuring the droplet size distribution over time helps monitor changes in emulsion stability. 5.Visual inspection: Emulsions are visually inspected for signs of phase separation, creaming, or coalescence. Techniques to enhance emulsion stability Cosurfactants: Cosurfactants are often used in conjunction with primary emulsifiers to improve emulsion stability. They can reduce interfacial tension and enhance the emulsifying properties of the system. Coalescence inhibitors: Additives known as coalescence inhibitors can be incorporated to hinder droplet coalescence, maintaining droplet size and overall stability. pH adjustment: Optimizing the pH of the emulsion can enhance stability by ensuring appropriate emulsifier solubility and charge.  Electrolyte control: Controlling the ionic strength and concentration of electrolytes can minimize their destabilizing effects on the emulsion. Particle size reduction: Techniques like high-pressure homogenization and microfluidization can reduce droplet size, leading to more stable emulsions. Use of stabilizing polymers: Polymers can be added to the formulation to provide steric stabilization, preventing droplet aggregation.  Parameter of quality control ▪ Physical appearance: Emulsions should be visually inspected for color, homogeneity, presence of sedimentation, creaming, or phase separation. ▪ Droplet size: Measuring droplet size distribution using techniques like laser diffraction or dynamic light scattering helps assess emulsion stability and uniformity. ▪ pH: pH measurement is essential to ensure that the emulsion remains within the desired range for stability and compatibility with the drug and skin (in the case of topical formulations). ▪ Viscosity: Viscosity determination is crucial for evaluating the flow properties and handling characteristics of the emulsion. ▪ Particle charge: For charged emulsions, zeta potential analysis provides information about the stability of the emulsion by assessing the electrostatic repulsion between particles. ▪ Density: Density measurement helps ensure proper mixing and uniformity in the emulsion.  Analytical techniques for emulsion characterization ✓Microscopy: Microscopic analysis allows visual inspection of emulsion droplets and can provide information about droplet size, shape, and distribution. ✓Droplet size analysis: Techniques like laser diffraction, dynamic light scattering (DLS), and nanoparticle tracking analysis (NTA) provide information on droplet size distribution and stability. ✓Rheology: Rheological measurements help determine the flow and viscoelastic behavior of the emulsion, which is crucial for topical applications and product stability. ✓Fourier-transform infrared spectroscopy (FTIR): FTIR can be used to analyze the interactions between the drug and excipients in the emulsion. ✓Differential scanning calorimetry (DSC): DSC helps evaluate the compatibility of the emulsion components and detect any phase transitions or incompatibilities. ✓High-performance liquid chromatography (HPLC): HPLC is used to quantify the drug content and assess drug stability in the emulsion. ✓Nuclear magnetic resonance (NMR): NMR spectroscopy can provide information about the molecular structure and interactions in the emulsion.  Quality check during manufacturing ✓Emulsification efficiency: Check the homogeneity and droplet size of the emulsion during the emulsification process. ✓pH adjustment: Monitor and adjust the pH as needed to ensure it remains within the desired range. ✓Viscosity measurement: Regularly measure the viscosity to ensure consistent product characteristics. ✓Emulsifier concentration: Check the emulsifier concentration to ensure proper stabilization. ✓Mixing time and speed: Monitor mixing time and speed to ensure proper dispersion of components. ✓Temperature control: Maintain proper temperature during the manufacturing process to prevent phase separation or other stability issues. ✓Visual inspection: Conduct visual inspections at various stages of production to detect any abnormalities or deviations from the desired physical appearance.  Challenges ❖Stability: Emulsions can be inherently unstable, with droplet coalescence and phase separation being common challenges during formulation and storage. ❖Particle size control: Achieving consistent and uniform droplet size distribution can be challenging, especially for large-scale manufacturing. ❖Compatibility: Some drugs may interact with emulsifiers or oils, affecting drug stability and efficacy. Formulators must carefully select excipients to ensure compatibility. ❖Manufacturing complexity: Emulsion manufacturing can be complex, especially for large- scale production. Achieving reproducibility and scalability can be challenging. ❖Regulatory compliance: Meeting regulatory requirements, such as cGMP, is crucial for emulsion manufacturers. Ensuring compliance and documentation throughout the process can be demanding. ❖Sensory attributes: Some emulsions, particularly for topical formulations, may have specific sensory attributes (e.g., appearance, texture) that need to be carefully controlled to ensure patient acceptability.