The formulation of aerosols requires careful selection and combination of ingredients to achieve desired performance.
Formulation Components of Aerosols:
Active Pharmaceutical Ingredient (API): Must be stable and uniformly dispersed or dissolved.
Propellant: As discussed, it drives the delivery mechanism and must be chosen based on its compatibility.
Co-solvents: Sometimes used to aid solubility or improve spray characteristics (e.g., ethanol).
Surfactants/Dispersants: Ensure proper dispersion in suspension aerosols and prevent aggregation.
Stabilizers and Antioxidants: Prevent degradation of sensitive APIs or excipients.
Manufacturing Process:
Batch Preparation: The API is combined with excipients under controlled conditions. For solutions, complete dissolution is necessary; for suspensions, uniform dispersion is critical.
Filling Process: The formulation is filled into pre-sterilized, pressurized containers using automated, high-precision filling lines designed to prevent air inclusion and contamination.
Addition of Propellant: The propellant is either introduced in bulk under pressure (in canister-based systems) or loaded separately in dual-chamber systems.
Crimping/Sealing: A valve is affixed to the container, and the system is sealed to maintain internal pressure and sterility.
Quality Assurance: In-process controls and final product testing (such as weight, fill volume, and dose uniformity) are essential.
Process Considerations:
Aseptic Processing: In many cases, especially for parenteral formulations, an aseptic environment is required.
Environmental Controls: Temperature, humidity, and particulate matter must be controlled during manufacturing.
Automation and Validation: The use of automated filling and sealing ensures uniformity and reproducibility.