Aerosols diagram, Classification, Components, Quality Control

Aerosols are pressurized packages in which products containing therapeutically active ingredients are dissolved, suspended, or emulsified in a propellant or solvent-propellant mixture intended for topical or intracavitary administration.

Synonyms:

1. Pressurized package

2. Pressurized packaging

3. Pressurized product

4. Pressure package

Advantages:

1. The pressure pack is easy and convenient to use.

2. In this dose can be removed without any contamination.

3. The sterility of the product can also be maintained.

4. The stability of drugs sensitive to oxygen and moisture can be increased.

5. The drug can be administered directly to the affected area in the desired form.

6. Irritation caused by mechanical application of topical medication is reduced or eliminated.

7. Dose regulation can be done using Metered valves.

8. Expensive drugs such as steroids and antibiotics may be delivered.

9. There is no risk of contamination of the unused part of the medicine in the container because the package is sealed

10. Ease of use and handling.

Disadvantage: 

1. It is expensive/ costly preparation.

2. Some of the propellants can be toxic.

3. It causes Allergic in some cases.

4. It may be Explosive.

5. Some formulations are difficult.

The Classification of Aerosols:

1. Based according to Particle Size:

(a) Space sprays

(b) Surface coating sprays

(c) Aerated sprays -foams

2. Based on Usage

(a) Topical aerosols -External use

(b) Inhalation aerosol / Oral aerosols- Internal use.

The Components of the Aerosol Package:

•  Propellant
•  Container
• Valve and actuator (valve assembly)
• Product Concentrate

1. Propellant

It is responsible for developing the power pressure within the container and also expelling the product when the valve is opened and in the atomization or foam production of the product.

Functions of propellants

1. Developing the correct pressure in the container.

2. Ejection of the product when the valve is opened.

3. Assist in atomizing or foaming the product.

4. Acts as a solvent and diluent.

5. Determination of product properties.

2. CONTAINERS FOR AEROSOLS

Containers used for aerosol production must withstand pressures up to 140 to 180 psig at 130oF. The following aerosol containers were used to package the aerosol products.

A: Metal Containers:

• Tin-plated steel:

1. Side-seam(Three-piece)
2. Two-piece or drawn
3. Tin free steeL

•  Aluminium: 

1. Two-piece
2. One-piece (extruded or drawn)

• Stainless steel 

B: Glass Containers:

• Uncoated glass
• Plastic-coated glass

A: Metal Containers

• Tin-plated Containers:

Tin-plated steel is used for aerosol cans to produce an aerosol can that is light and relatively cheap. A tin-plated steel container consists of a sheet of steel plate that is electroplated with tin on both sides.

B: Glass Containers

Advantages:

1. Glass containers are preferred containers for drugs/pharmaceuticals due to the absence of incompatibilities.

2. Glass containers look good.

3. Glass is fundamentally stronger than most metal containers.

4. The Glass allows a greater degree of freedom in the design of the container.

Limitations:

1. If the container is accidentally dropped, the container will break and the entire contents will be lost.

2. Glass containers are limited to lower and lower-pressure products

percentage of propellant.

Types of Glass Containers:

1. Uncoated glass containers

2. Plastic-coated glass containers

1. Uncoated glass containers:

These containers have the advantage of lower costs and high clarity. The Content can be viewed at any time through Uncoated glass containers

2. Plastic-coated glass containers:

These are protected by a coating that prevents the glass from breaking if broken.

3. VALVES

Use of valves:

1. The valve has a fundamental influence on the character of the product being dispensed.

2. The valve can be opened and closed easily.

3. The valve is capable of delivering the contents in the required amount iif necessary and preventing loss at other times.

4. The valve can deliver a given amount of medicine.

It consists of many parts made up of different materials

1. Ferrule or Mounting Cup:

 Ferrule is made up of tin-plated steel (rarely aluminum).

2. Valve Body or Housing:

• The case is made of nylon or Delrin.
• The housing contains a hole at the point of connection of the immersion tube, which varies from approximately 0.013 to 0.08 inches.

3. Stem:

• The stem is made from nylon, Delrin, Brass, and SS.
• The stem contains one or more orifices.

4. Gasket:

• The gasket is made from Buna-N and Neoprene rubber.
• These gasket materials are compatible with most pharmaceutical formulations.

5. Spring:

•  The spring is made from SS
• Thespringservestoholdthegasket.

6. Dip Tube:

• The dip tube is made from polyethylene or polypropylene.
• The inner diameter of the commonly used dip tube varies

7. Actuator:

The actuator is a specially designed button fitted to the valve stem.

They are:

(i) Spray actuators

(ii) Foamactuators

(iii) Solid stream actuators

 (iv) Special actuators

QUALITY CONTROL OF AEROSOLS:

A: Flammability and flammability tests

1. Flash point:

• A standard open cup apparatus is used to determine the flash point aerosol product.
• The product is cooled to -25oF.

2. Flame Projection:

• The product is sprayed for about 4 seconds in the flame. Depending on the nature of the formulation, the flame is prolonged.
• The length of the extended flame is measured.

B: Physico-chemical properties

1. Vapor pressure:

• Vapor pressure is determined by a pressure gauge.
• Fluctuations in the vapor pressure in the containers indicate the presence of air in the headspace of the container.

2. Density:

• The density of an aerosol system can be accurately determined using a hydrometer or pycnometer.

3. Moisture content:

• The Karl Fischer apparatus is used to determine moisture content.

4. Identification of propellants:

• Gas chromatography and infrared spectrophotometry were used to identify propellants.

C: Performance

1. Aerosol valve Discharge Rate:

2. Spray pattern : 

• The spray pattern of aerosol valve discharge is determined as follows.
• An apparatus consists of a motor-driven rotating disc with an adjustable slit.

3. Dosage with metered valves:

When one attempts to test this, then either of the following must be observed.

(i) Reproducibility of dosage each time the valve is depressed. 

(ii) Amount of medication received by the patient.

4. Foam Stability: 

The life of a foam can range from a few seconds to one hour or more.

5. Particle size determination: 

• To determine particle size cascade impactor is used. 
• The principle behind the working of cascade impactor.

6. Leakage:

• Pass the crimped aerosol containers through the water bath. If any leaks are present, the evolution of air bubbles can be observed and the container is rejected.

D: Biological Characteristics

1. Therapeutic Activity: 

Testing of aerosols for therapeutic activity is similar to testing of non-aerosol products. Apart from regular tests, dosage is testing for inhalation aerosols. 

2. Toxicity: 

Toxicity testing includes the following;

(i) Irritation of the affected area where the dose is administered.

(ii) Chillingofskinduetoevaporationofpropellants.

Frequently Asked Questions