Considerations for the Development of Nasal Dosage Forms
5.6 Manufacturing and Filling Nasal Delivery Systems
5.6.1 Aseptic Manufacture
Various sterilization processes are employed for both the container/closure system (for example, glass containers are subjected to dry heat; suitable plastic containers such as high density polyethylene are subjected to ionizing radiation; rubber clo-sures are subjected to moist heat) and the dosage form. Some options for producing a sterile dosage form are presented below.
5.6.1.1 Sterile Filtration
If the dosage form is a liquid solution, or a very low viscosity emulsion, sterilization can be affected by passing the solution through a fi lter with a pore size small enough to trap out any microbial contamination (0.2 μm). The fi ltered dosage form is then kept sterile until it is enclosed in the fi nal container/closure system (see Fig. 5.11 ).
During process development, an assessment of the fi lter and fi ltration process must be carried out—including:
• Retention of the drug substance by the fi lter/loss of potency—by testing the dos-age form pre- and post-fi ltration
• Testing the fi lter for potential extractables and leachables
• Testing the fi lter for microbial retention
Fig. 5.10 Unit-dose powder (UDP) and bi-dose powder (BDP) devices (courtesy of Aptar Pharma)
The bioburden of the pre-fi ltered solution must be evaluated as part of the in- process testing to ensure that the fi lter does not become overloaded with contami-nants. The integrity of the fi lter must also be checked following the fi ltration process.
Filtration cannot be used as the sole means of achieving a sterile bulk formula-tion in the case where the dosage form is viscous or contains suspended particles (for viscous or suspension formulations, see Sect. 5.6.1.2 ). The following case study summarizes work carried out to validate a sterilizing fi lter.
Case Study: Sterilizing Filter Validation Purpose
The purpose of this study was to demonstrate that the sterilizing fi lter was acceptable and capable for the sterile fi ltration of the product base. This was achieved through a review of the supplied fi lter documentation, and by carrying out various verifi ca-tion activities.
Fig. 5.11 Sterile fi ltered dosage form
Verifi cation Requirements and Results
The critical operating parameters associated with the sterile fi ltration of the product base (temperature, fl ow rate, and pressure) that could potentially impact the perfor-mance and integrity of the fi ltration process must be within the design capability of the fi lter cartridge/membrane. Table 5.6 lists the verifi cation requirements for the sterilizing fi lter, the acceptance criteria, and the results obtained.
5.6.1.2 Combination Processes
In cases where fi ltration cannot be used as the sole means of sterilization (for example, for viscous or suspension formulations), there are several combination processes available.
Dry Heat or Ionizing Radiation of Powders Followed by Aseptic Addition to Pre-fi ltered Base
Here, the powders are fi rst packed into a suitable container, and then subjected to sterilization by dry heat (e.g., 170 °C for 1 h) or ionizing radiation (gamma or elec-tron beam). The liquid formulation base is sterilized by fi ltration. The sterile powder is then added to the sterile formulation base by aseptic addition—for example, via a presterilized isolator attached to the mixing vessel (Fig. 5.12 ). Factors to consider when presterilizing powdered active ingredients include heat stability of the active ingredient; stability to ionizing radiation; packaging of the active ingredient; com-patibility between the active ingredient and the packaging; and extractables and leachables from the packaging .
Aseptically Combining Phases Sterilized by Different Methods
Here, the bulk formulation is split into two distinct phases—for example, the oil and aqueous phases of an emulsion. The drug substance is dissolved in one of the phases.
The oil phase is then sterilized by passing it from a phase tank into the fi nal mixing tank, via a 0.2 μm fi lter; the aqueous phase is autoclaved in a second phase tank.
These two phases are then combined in a fi nal mixing tank, and held sterile until packaging (Fig. 5.13 ).
Once the bulk formulation has been produced sterile, the manufacturing environ-ment for the downstream processes (fi lling and closing the nasal delivery system) needs to be kept and monitored at a very high quality (low bioburden and particulate levels). The whole manufacturing process needs to be validated at regular intervals (usually every 6 months) to demonstrate that the aseptic handling techniques and manufacturing operations do not compromise the sterility of the fi nal product.
This validation exercise involves carrying out media simulations, processing micro-biological growth media through the entire process train and into the fi nal container/
Table 5.6 Verifi cation requirements for fi lter sterilization
Test Description Acceptance criteria Results Membrane
attributes
Verifi cation performed to document the pore size of the fi lter membrane in order to assess the retention capability by design
Filter membrane pore size, by process design, is to be a 0.22 μm size for microbial retention
Pore size was confi rmed to be 0.22 μm
Verify physical size—for information only
Document membrane characteristics for information only
Thirty (30) inches in length, with an effective fi ltration membrane surface area of 22 ft 2 (2.1 m 2 ) Pyrogens Verify that the fi lter is
appropriate for use with sterile processes
USP Pyrogen test was performed to confi rm that the fi lter cartridges are non-pyrogenic and suitable for parenterals
Meets current USP
<151>
requirements
Bacterial endotoxin
Verify that the fi lter cartridge meets USP requirement for parenteral use,
<0.5 EU/mL
USP Bacterial Endotoxin test was run (using a solution of cartridge extract mixed with Limulus Amebocyte Lysate) to confi rm that the fi lter cartridges are not contaminated with endotoxin
Extractables contain
<0.066 EU/mL bacterial endotoxin (as determined using LAL test)
Material compatibility
Verify that the membrane meets USP require-ments for the intended application (non- shedding/nonreactive)
Filter membrane must be constructed of non-shedding and nonreactive material
Polyvinylidene fl uoride (PVDF) membrane and polypropylene components USP Class VI Plastic Meets criteria for
non-fi ber releasing fi lters as defi ned per Title 21 of the Code of Federal Regulations (CFR) parts 211.72 and 210.3 (b) (6) Process
capability
Verify that the fi lter membrane is designed to meet the require-ments of the
manufacturing process
Must meet the following:
• Max. 25 psi pressure at 80 °C (product temp)
• Sterilizing grade (capable of tempera-tures ranging from 121 to 123 °C)
Membrane design attributes:
• ≥25 psi at 80 °C • Sterilizing grade
(for temperatures up to 126 °C)
(continued)
closure system—and needs to include all anticipated process interventions, manual and mechanical manipulations, and machine downtime. The media is then incu-bated to determine if the process is contamination-free. If contamination is found, the contaminants need to be identifi ed, and causes assigned to the failure of the aseptic operation.
In an aseptic operation, controlling the sterility of the drug product and con-tainer/closure system is relatively straight forward; it is the human interface that provides the biggest challenge and the most likely cause of contamination.