Containers and Closures of Parenteral Product

Any container for parenteral product should maintain the integrity of the product as a sterile, pyrogen-free, high purity preparation till it is used. It should also be attractive, allow the withdrawal of the contents and be strong enough to withstand processing and shipping; and finally it should not interact with the product.

Glass seems to be the material of choice for containers for parenteral products. Glass containers may either be sealed or closed with rubber stoppers. Containers of Type-I glass are best for aqueous preparations.

Siliconization i.e. the application of a thin film of silicone to coat the inside surface of the vials and ampoules, has been employed to prevent interaction of the product with the glass surface. The process also minimizes adsorption of active ingredients from homogeneous solutions, prevents adsorption of solids from suspensions and prevents aggregation at the glass surface in colloidal preparations.

Plastics used in the packaging of parenteral products are based on polyethylene or polypropylene. Plastic containers are much less used as compared to glass but the former are becoming increasingly popular for intravenous fluids.

Only polypropylene containers can withstand sterilization by autoclaving. Many plastics contain additives like plasticizers, antioxidants, antistatic agents and lubricants. These additives may leach out from the plastic into the product. Most plastics selectively permit passage of chemical molecules and are permeable to gases. Plastics are extensively used for containers of administration sets particularly disposable type.

As compared to glass, plastics are light weight, less fragile and easy to handle but most of them are not as clear as glass.

Rubber is the material of choice for closures for multi-dose vials, intravenous fluids bottles, plugs for disposable syringes and bulbs for ophthalmic pipettes. Rubber closures permit the introduction of a needle from a hypodermic syringe into a multi-dose vial and provide for resealing of the vial after the needle is withdrawn.

Rubber closure is held in place by an aluminium band. Such closures are composed of several ingredients, basic structural unit being a linear unsaturated hydrocarbon, isoprene. All or part of the natural polymer is sometimes replaced by a variety of synthetic rubber polymers. In addition, a vulcanizing agent usually sulphur; an accelerator e.g., 2-mercaptobenzothiazole; an activator, usually zinc oxide; fillers such as carbon black or limestone; antioxidants and lubricants etc., may also be present in rubber closures. These substances may be leached into the product or may cause chemical interaction.

Lacquer or plastic coating applied to the surface of the rubber closures in contact with the product may partially reduce leaching and also permeation. Another most commonly encountered problem with rubber closures is that of coring i.e., the generation of rubber particles cut from the closures when needles are inserted; the particles are known as cores. Selection of the proper gauge needle and its proper use may minimize the problem of coring.