Media Fill Test for Sterile API Manufacturing Process

Media Fill Test for Sterile API Manufacturing Process

Know about the process simulation test for the active pharmaceutical ingredient (API) manufacturing process.

Media fill test is done to verify the sterility of the sterile manufacturing process. Media fill validation for sterile API is different from the sterile formulation media fill.

There are different processes in the sterile API manufacturing as filtration, crystallization, drying, milling etc. These all are different from the sterile formulation process where the sterile material is filled in sterile containers in aseptic conditions. Lactose powder is used in the process simulation.

The whole media fill process is carried out in two phases

1) Wet Phase 

2) Dry phase

1) Wet Phase: 

Non-sterile lactose powder is used in the wet phase. Wet phase simulates the liquid processing steps of the manufacturing process i.e. aseptic filtration of lactose solution from controlled area reactor to crystallizer of the aseptic zone. The non-sterile lactose solution is sterilized by aseptic filtration, through filtration train of sterilizing-grade filters.

A solution of non-sterilized lactose powder is prepared with water for injection (WFI) and filtered through the plate & frame filter and lactose solution is transferred to the crystallizer. Water is added as a solvent in the crystallizer through the solvent transfer line. Now complete solution from the crystallizer is filtered through a pre-sterilized 0.45µm filter of 142 mm diameter, under air pressure of NMT 1.0 Kg under aseptic conditions.

After the completion of filtration, the filter is aseptically removed and placed onto pre-incubated 200 mm diameter SCDA media plates. These SCDA media plates are immediately transferred to the microbiology laboratory and incubated at 22.5 + 2.5°C for 7 days and 32.5 + 2.5°C for next 7 days and count the colony forming units (cfu).

2) Dry Phase: 

Pre-sterilized lactose powder is used in the dry phase of the process simulation test. This phase simulates the powder processing steps of the manufacturing process i.e. from Nutsche Filter, Vacuum Tray Drying, Powder Filling, Milling, Blending and filling in a sterilized aluminum canister.

Pre-sterilized lactose powder is charged in Nutsche filters and kept on hold for a time period of 6 hours, to simulate the slurry filtration time during normal production batches. Nutsche filter is transferred to VTD room. Lactose is transferred to VTD trays by using pre-sterilized scoops. The total quantity is distributed in VTD trays. On completion of the contact time of Lactose in VTD, the VTD trays are unloaded in pre-sterilized SS Bins.

Lactose is passed through the Multi-mill and the milled lactose powder is collected in sterilized SS Bins. Lactose powder is further charged in the blender and blending is done for 2 hours to simulate the longest blending time. Lactose is unloaded in depyrogenated aluminum canisters to simulate the filling operations. These canisters are sealed and manually rotated & shaken so that lactose can get in contact with the internal surface of the canister as well as the closure.

Now sterile lactose (5 kg capacity canisters) is charged aseptically in a blender. Blended lactose is filled in aluminum canisters to simulate blend batches. As a parallel activity, the critical area crystallizer is charged with 1100 liters of WFI through 1.2 µm, 0.2 µm & 0.2 µm filters, for dissolving lactose (less than 10 % Lactose solution).

Lactose from the filled aluminum canister is charged aseptically into the crystallizer through the manhole and agitated to dissolve lactose.

A filtration assembly, with a membrane filter holder, is attached to the bottom line of crystallizer and the complete lactose solution is aseptically filtered through pre-sterilized 0.45 µm filter of 142 mm diameter, under air pressure of NMT 1.0 Kg.

After the completion of filtration, the filter is placed on 200 mm diameter, pre-incubated SCDA media plates. These SCDA media plates are immediately transferred to the microbiology laboratory and incubated at 22.5 + 2.5°C for 7 days and 32.5 + 2.5°C for next 7 days and count the colony forming units (cfu).

Samples can be collected for sterility at the completion of various stages as at the time of unloading of VTD, multi mill and blending.

Note: Time for each activity must be similar to the actual manufacturing process for the product.

Acceptance Criteria: Contamination in one unit in 10,000 units is acceptable for media fill; it means 0.01% contamination is acceptable. In bulk manufacturing where sterile API is filled in large quantities in containers; how to calculate the percentage of units?

Therefore, in API media fill the acceptance criterion is different from the formulation. Here the whole batch is converted into the number of units. For example: Ceftriaxone Sodium batch of 160.00 Kg has injectable formulation units of 250 mg, 500 mg and 1 g available in the market, then 100.00 Kg batch is to be converted into 1gm (highest strength) vial units i.e. number of vials = 160,000gm / 1gm/vial = 1,60,000 units.

a) Now, suppose 10 CFUs (colony forming units) are observed after incubation period is over, the contamination rate calculation shall be (10 units/1,60,000 units) x 100 = 0.00625 %. Since actual contamination of 0.00625% is less than the limit of 0.01%, therefore this contamination rate would be acceptable.

b)  Suppose 16 CFUs (colony forming units) are observed after incubation period is over, the contamination rate calculation shall be (16 units/1,60,000 units) x 100 = 0.01 %. Therefore this contamination rate shall not be acceptable.