Glass Containers used in Pharmaceuticals

Types of Glass Containers used in Pharmaceuticals

Pharmaceutical glass containers are designed to come into direct touch with pharmaceutical products.

Glass used for pharmaceutical containers is mainly two types (As per USP),

Borosilicate (neutral) glass (Type I)
Soda-lime-silica glass. (Type II & Type III)

The glass network of borosilicate glass contains considerable concentrations of (80%) Silica, boric oxide (10%), aluminium oxide, and alkali and/or alkaline earth oxides.
Borosilicate glass considers being to have a high thermal shock resistance & a high hydrolytic resistance due to the chemical composition of the glass. So, it is classified as Type I glass.
The glass network of soda-lime-silica glass consist of alkaline metal oxides, primarily sodium oxide, and alkaline earth oxides, primarily calcium oxide.
Because of its chemical composition, soda-lime-silica glass has a low hydrolytic resistance; it is categorised as Type III glass.
The hydrolytic resistance of Type III soda-lime-silica glass containers will be increased from a moderate to a high level after “suitable treatment,” changing the categorization of the glass from Type III to Type II.
Type IV glass containers (Type NP glass/General-purpose soda lime glass): The hydrolytic resistance of this sort of glass container is low. This sort of glass container should not be used for autoclaved products since it will enhance the glass container’s erosion reaction rate.

The Different types of glass containers used in pharmaceuticals are briefly discussed below,

Glass Classification	Name of Glass
Type I	Neutral glass. Type 1 glass is also known as Borosilicate glass
Type II	High level of hydrolytic resistance (soda-lime-silica glass)
Type III	Moderate hydrolytic resistance (Regular or Uncoated soda lime glass)

Types of Glass Containers used in Pharmaceuticals

Use of Glass Containers used in Pharmaceuticals based on Type of Glass.

Type of Glass	Uses
Type I (Borosilicate (neutral) glass)	Type I glass containers are appropriate for most products for parenteral and non-parenteral uses.
Type II (soda-lime-silica glass/ treated soda-lime glass/ De alkalized soda lime glass)	Most acidic and neutral aqueous products for parenteral and non-parenteral use can be stored in Type II glass containers. When stability data proves their compatibility, Type II glass containers can be utilised for alkaline parenteral materials/products.
Type III (Regular soda lime glass)	Except if sufficient stability test findings indicate that Type III glass is satisfactory, Type III glass containers are rarely utilised for parenteral medications or powders for parenteral use.
Type IV glass containers (Type NP glass)	It can be used to store topical products and oral dosage forms.

Glass Containers for Pharmaceutical Use

Evaluation studies on glass containers:

Hydrolytic resistance – inner surfaces of glass containers

Surface glass test (USP <660>): Type I and Type II glass containers are distinguished from Type III glass containers by this symbol. It is based on the hydrolytic resistance of glass container interior surfaces.

Surface test (As per Test A – EP Chapter 3.2.1)

Hydrolytic resistance of glass grains:

Powdered glass test (USP <660>) and

Glass grains test (Test B – EP Chapter 3.2.1): Type I glass is distinguished from Type II and Type III glass by the usage of this term.

Arsenic Release (containers for aqueous parenteral preparations)

USP <211> Arsenic and
EP Chapter 2.4.2 Arsenic

Spectral transmission for coloured glass containers (Specifically Amber coloured):

light transmission and
UV resistance (applies to coloured containers)

Others,

Testing USP <1660>, Delamination and ICHQ3D Studies
Surface etching test : Useful to determine whether the containers have been surface-treated or not.
Delamination assessments in accordance with the guidance in <1660>
Extractables testing as per ICH Q3D

Factors which influence a glass container’s selection

A number of factors influence the decision to choose glass containers as primary packaging. These elements include:

The glass container’s alkalinity limit and hydrolytic resistance
The glass container’s thermal expansion properties (freeze-drying)
The glass container’s sensitivity to barium or calcium ions

Advantages glass containers

Because of their rigidity and better protective characteristics, glass containers are commonly used to package liquid solutions.
Its extreme transparency makes it simple to inspect its contents.
Because it is relatively impervious to air and moisture, it provides excellent protection.
Most therapeutic products are chemically resistant to it.
Certain wavelengths of ultraviolet light and certain wavelengths can be protected by coloured glass (amber glass and red coloured glass).
Heat sterilisation of glass containers is simple.

Disadvantages glass containers

Glass containers are costly to produce.
They’re delicate and somewhat weighty.
Some types of glass containers have a tendency to lose some silica into the formulation during heat sterilisation.

General Process for Glass Container Forming:

The process of glass container forming involves several steps to shape molten glass into the desired container shape.

The most common method used in the pharmaceutical industry is the glass-blowing technique. Here is an overview of the glass container forming process:

1. Glass Melting: The process begins with the melting of raw materials, such as silica sand, soda ash, limestone, and other additives, in a furnace at high temperatures. This results in molten glass.

2. Glass Gob Formation: The molten glass is then fed into a machine called a gob feeder. The gob feeder shapes the molten glass into small, uniformly sized portions known as gobs. The size of the gob determines the size of the final glass container.

3. Mold Preparation: The molds used in glass container forming are typically made of metal and consist of two halves, the blow mold, and the neck ring. The molds are carefully cleaned and coated with a lubricant to prevent sticking.

4. Gob Delivery: The gobs are transported to the forming machine, which positions them above the open molds. The gob is then dropped into the mold cavity.

5. Container Formation: The two halves of the mold close together around the gob. Compressed air is then blown into the mold through the blowhead, which causes the molten glass to expand and take the shape of the mold. The air pressure is carefully controlled to ensure uniform container thickness.

6. Parison Formation: The initial expansion of the molten glass forms a shape called a parison. The parison is a hollow glass container with a small opening at the top, known as the finish. The finish will later be formed into the desired shape for attaching closures.

7. Cooling and Annealing: Once the container shape is formed, the molds open, and the newly formed glass container is transferred to a conveyor system. The containers are then cooled gradually in a controlled manner to relieve internal stresses and improve their strength and durability. This process is known as annealing.

8. Finishing Operations: After annealing, the glass containers undergo various finishing operations, including trimming excess glass, flame polishing to smooth the edges, and inspecting for any defects or imperfections.

9. Quality Control Testing: Samples from each batch of glass containers may undergo quality control testing to ensure their dimensional accuracy, strength, and integrity. Tests such as burst pressure testing, leak testing, and visual inspection are commonly performed.

10. Packaging and Storage: The finished glass containers are then packaged, usually in protective trays or boxes, to prevent breakage during transportation and storage. Proper labeling and documentation are essential for traceability and regulatory compliance.

Reference:

<660> CONTAINERS—GLASS

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