Creating a contaminant and/or vacuum-free drug delivery device, such as an inhaler, nasal pump, or eye dropper, is a difficult task. This article examines a venting option that enables a closed, equalized system for multiunit-dose drug packaging.

By Michele Crane
As the pharmaceutical industry moves toward delivering multi-dose preservative-free products, the delivery device manufacturer faces a three-fold challenge—creating a system that guarantees accurate dosage, maintains a sterile environment inside the container, and minimizes leakage and exposure to the pharmaceutical agent.

Gore membranes breathe while repelling liquid, particles and bacteria.
When using a drug delivery device such as a pump, dropper, or squeeze bottle, the force used to dispense each dose creates a sudden drop of pressure that must be equalized inside the device. Allowing the device simply to draw in air through the dispenser prevents a vacuum from forming, but the air drawn in from the outside environment may contain bacteria that can potentially contaminate both the pharmaceutical product and the dispensing chamber. So, the device designer is faced with the problem of allowing for the free exchange of airflow without compromising the sterile environment of the drug and without allowing the drug to leak out of the container.

While mechanical closed systems can manage the pressure differential that occurs with dispensing, these systems are complex, expensive to implement, and can often stick and leak during use. Also, the outside unfiltered air that is drawn into the dispenser may compromise the efficacy and sterility of the drug.

An alternative solution to this design issue is to create a closed system using a microporous material that allows air to flow freely in and out of the device but, at the same time, creates a barrier against contaminants and other microorganisms. Replacing the dispensed drug with filtered air equalizes the pressure and eliminates the vacuum inside the device. Using a venting material as the air intake-source, rather than the nozzle or dropper, minimizes the ingress of contaminated fluids or air. The problem then becomes preventing the pharmaceutical agent from leaking out of the device while preventing contaminants from entering the device through the vent, thus compromising the sterility of the drug.

Using a Gore membrane made of expanded polytetrafluoroethylene (ePTFE) addresses all three issues: airflow, contamination, and leakage. First, the microporous structure of the membrane allows for the free exchange of airflow, equalizing the pressure in the dispenser after each dose is administered. Because of their optimized airflow and filtration efficiency, Gore membranes have been used as bacterial barriers in medical devices such as IV spike vents and filter vents, reconstitution devices, and gas analyzers for over 25 years.

Second, ePTFE is naturally hydrophobic and inert. In addition, it has low extractables, making it ideal for pharmaceutical contact. Gore membranes repel fluids and other aerosols that threaten the sterility of multi-dose pharmaceutical products by blocking airborne particulates and pathogens from entering the device. Combining the hydrophobic and porous characteristics of Gore membranes means that as air flows in and out of the device, it is filtered for liquid and solid contaminants, which reduces the risk of viral and bacterial contamination of the drug.Third, because the ePTFE membrane repels fluids, it prevents the pharmaceutical agent from leaking out of the mechanism, maintaining package integrity and minimizing unnecessary exposure to the active components of the drug.

Drawing on nearly 50 years of research in expanded polymer technology, W. L. Gore & Associates Inc. has developed a complete line of ePTFE membranes with a microbial barrier protection efficiency of up to 99.9999%. According to John Tomanovich, senior product specialist for Gore, “The key to successful venting is selecting the right membrane. Factors that affect this decision include such things as the surface tension of the pharmaceutical agent, sterilization methods, chemical compatibility, storage temperature, size of the device, and integration of the vent into the device.”

At one time, determining dosage of a drug was solely the responsibility of the drug manufacturer. However, as the pharmaceutical industry continues to move toward multi-dose, preservative-free products, the delivery device manufacturer is becoming much more involved in maintaining the integrity and accuracy of each dose. Tomanovich adds, “Using closed systems for this purpose is clearly the direction to go with device design, but the device manufacturer must also consider reliability, cost, and design integration. Gore membranes have demonstrated that they enable a cost-effective, safe, and effective closed system for multi-dose delivery of pharmaceutical products.”

For additional information on the technologies and products discussed in this article, visit W. L. Gore & Associates Inc. at

Michele Crane is a new business development associate for W. L. Gore & Associates Inc. She is responsible for new product and market development for non-implantable, external medical devices and pharmaceutical applications. Ms. Crane can be reached at 410-506-8833 or