Introduction to the Full Process of Pre-filled Syringe Product Filling Production

Originally, injections were administered using ampoules. Before injection, the neck of the ampoule was broken, and then the liquid medicine was drawn into a syringe and injected into the body. The risk with ampoules is that the sharp glass can easily cut the skin, and the remaining medication can cause adverse reactions in those who come into contact with it. In addition to ampoules, an additional syringe is also required. Therefore, after years of development, pre-filled syringes and injection pens, which load the medication into the syringe, have emerged.


Currently, pre-filled syringes are the preferred drug delivery devices for at least 50 types of injectable drugs and vaccines. Data shows that the global pre-filled syringe market is projected to reach $7.328 billion by 2027. Many pharmaceutical companies are increasingly inclined to use pre-filled syringes as a method of drug delivery, especially for antibody-based drugs. Compared to traditional syringes and drug packaging materials, pre-filled syringes have significant advantages, such as reducing preparation steps, lowering the risk of medical errors and microbial contamination, improving product utilization, saving time, and ensuring product quality and performance.


Pre-filled syringes and injection pens are new types of pharmaceutical packaging materials that are not considered medical devices but rather components of drug packaging systems. They have the functions of storing drugs and enabling injections. Pre-filled syringes and injection pens can be used for precise dose control in long-term care, improving treatment effectiveness and enhancing patients’ quality of life. Furthermore, they help eliminate intermittent treatment, achieve quantifiable adjustments, reduce adverse effects, and improve treatment efficiency. Pre-filled syringes are mainly used for packaging vaccines, biologics, biochemical products, anticoagulant drugs, and other products, while injection pens are commonly used for self-administration of insulin and similar medications by patients.

prefilled syringe

This article provides a brief introduction to the production process of aseptic filling for pre-filled syringes (also known as pre-filled needles), explaining how the liquid medication is filled into pre-filled syringes or injection pens through multiple steps. The production of aseptic filling generally uses ready-to-use pre-filled syringes and stoppers, employing ready-to-use packaging materials for production. The production process mainly includes unpacking the outer packaging, unpacking the inner packaging, filling, stoppering, inspection under light, rotating the plunger, labeling, and packaging.


The common production process for pre-filled syringe filling is as follows:

Key process control points for each operation:


01. Unpacking the outer packaging

The process of unpacking the outer packaging involves transferring commercially available ready-to-use pre-filled syringes into the filling machine. The unpacking process should be performed in an A-grade laminar flow protection environment. During the entire unpacking process, care should be taken to avoid contamination of the nest box and the environment by particles and microorganisms from the outer bag. Usually, the outer packaging needs to be manually cleaned, wiped, and disinfected before unpacking to reduce the presence of particles and microorganisms on the outer packaging bag.

02. Unpacking the inner packaging

The process of unpacking the inner packaging is performed in a sterile A-grade environment. To prevent particles from entering the syringe during film tearing and vacuum transfer, it is necessary to avoid excessive movement that may generate particles during film tearing and transfer of the pad. Additionally, laminar airflow should be utilized to protect the syringe from particle contamination. Real-time online particle monitoring should be conducted in this area to assess and control the impact of particles generated during the inner packaging unpacking process. To reduce the risk of microbial contamination and minimize manual operations in unpacking the inner packaging, an automated unpacking process is preferred.

03. Filling and stoppering

During the filling process, sterile operation by personnel should be ensured, and interference with the production process by personnel should be minimized. The filling speed should be controlled to ensure accuracy, and the filling volume should be regularly checked. The use of an online weighing system is recommended. If an online weighing system is employed, calibration should be performed before production. In the stoppering process, the rubber stopper is subjected to significant compression and friction when forced out of the sheath, which may lead to problems such as damage to the stopper, particle generation, and deformation of the sealing line. Therefore, during the debugging and confirmation of the stoppering equipment, inspection and confirmation of the size and roughness of the sheath are necessary to minimize stopper damage and ensure the sealing integrity and asepticity of the pre-filled syringe.

04. Sterilization

The sterilization process for pre-filled syringe products differs from that of other final sterilized products. In addition to controlling the temperature and time during sterilization, it is also necessary to maintain a balanced pressure difference inside and outside the product.

05. Inspection under light

If manual inspection is conducted, the illumination of the inspection equipment should be verified to ensure it meets the requirements. If an automated inspection machine is used, the equipment parameters should be confirmed to meet the process requirements, and the machine should be tested using defective products before inspection.

06. Plunger rod insertion and labeling

The torque rotation or force required during the plunger rod insertion should be verified. Excessive plunger rod insertion may cause displacement of the syringe barrel and stopper, resulting in abnormal sealing and compromising product asepticity. Therefore, challenges related to the plunger rod insertion process should be considered during media fill simulations.

07. Blister packaging

It should be confirmed that the pre-filled syringe is properly installed in the slot, and the placement direction of the syringe meets the specified requirements.

08. Boxing

Before boxing, it is necessary to confirm the accuracy of batch number, production date, and expiration date information. QA should verify the printed information before printing, and during production, periodic confirmation of complete and accurate printing information is necessary. If an online monitoring device is used, defective products should be used before production to confirm the effectiveness of the online monitoring device.

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