Evaluation of Aerosol | Pharmaceutics

Evaluation of pharmaceutical aerosol can be done by a series of physical, chemical, and biological tests to ensure proper performance of the package and safety during use and storage.

Flammability, Combustibility, Flash point, Flash Extension & Flashback, Vapour Pressure, Density, moisture content, Propellants, Valve Discharge rate, Foam stability, Net Content, Spray Pattern, meter value, safety, — Evaluation of Pharmaceutical Aerosol

1. Flammability & Combustibility

a) Flash Point

b) Flash extension & Flashback

2. Biological Testing

i) Therapeutic efficacy/activity &
ii) Toxicity

3. Physicochemical characteristics

i) Vapour Pressure

ii) Density

iii) Moisture content

iv) Identification of Propellants

v) Concentration propellants ratio

4. Performance

a) Aerosols valve discharge rate

b) Leakage

c) particle size determination

d) Foam stability

e) Net content

f) Spray pattern

g) Dosage with meter valve

1. Flammability & Combustibility

a) Flash Point

In order to determine the flash point of an aerosol, two basic apparatus types are available which are an open cup and closed cup.

Apparatus: Open Cup Tag Apparatus

Flash-point test is done by cooling the temperature of the aerosol product to 25F.

Test liquids temp. is allowed to increase slowly & temp. at which vapors Ignite is called as Flash Point.

Open cup tag apparaturs, Aerosol, Flash point — **Open Cup Tag Apparatus**

Closed cup tests

Closed cup tests purpose to simulate the situation of a fluid spill in a closed environmental condition.

In closed cup tests to determine the flash point the investigated sample is placed inside a sealed test cup and introduced to a potential ignition source, determining the temperature at which the sample flashes.

An open cup apparatus will constantly give a higher flash point than a closed cup one as the open cup permits loss of internal vapors to the atmosphere above the apparatus.

b) Flash extension & Flashback

This type of evaluation test is also known as the flame projection test. Product is sprayed through an open candle flame for about 4 seconds at a fixed distance of 6 inches. (15 cm), & the flame’s extension is measured in (cm) and recording the length of the flame projection. An aerosol product is judged flammable if its flame extends 18 inch. (46 cm) or more through an open flame, or if the flame flashes back to the actuator.

2. Biological Testing

i) Therapeutic efficacy/activity

For Inhalation Aerosols is depends on the particle size.
For Topical Aerosols is applied to test areas & adsorption of therapeuticingredient is determined.

ii) Toxicity

For Inhalation Aerosols:- exposing test animals to vapor sprayed fromAerosol container.
For Topical Aerosols:- Irritation & Chilling effects are determined

3. Physicochemical characteristics

Property	Method
Vapour Pressure	Can Puncturing Device Pressure Gauge
Density	Hydrometer Pycnometer
Moisture content	Karl Fisher method Gas Chromatography
Identification of Propellants	Gas Chromatography IR Spectroscopy

Physicochemical characteristics of Aerosols

4. Performance

a) Aerosols valve discharge rate

Content of the aerosol product of known weight is discharged for a specific period of time.
By reweighting the container after the time limit, the change in the weight per time dispensed gives the discharge rate (gram per second).

b) Leakage

It is done by measuring the Crimp’s dimension & comparing. Final testing of valve closure is done by passing filled containers through water bath.

c) particle size determination

Particle size of aerosol product are determined by Cascade Inspector and light scattering decay.

Cascade Inspector

Principle: Stream of particles projected through a series of nozzle and glass slide at high velocity, larger particles are impacted first on lower velocity stages and smaller particles are collected at Higher velocity stage.

Light scattering decay

Principle: An aerosol settles under turbulent conditions the change in the light intensity of a tyndall beam is measured.

d) Foam stability

some foam have a lifetime of a limited few seconds and those known as “quick breaking” foam, while other foams can persist up to hours.

Various Methods to check foam stability are:

Visual methods
Time for given mass to penetrate the foam &
Time for given rod that is inserted into the foam to fall.
Rotational viscometer

e) Net content

Tared Cans that have be placed on to filling line are reweighted and the different in the weight is equal to the net content.
In destructive method, weighting a full container and then dispensing as much as possible of the content. The content are then weighted. This gives the net content.

f) Spray pattern

The method is based on impingement of spray on piece of paper that has been treated with Dye-Talc mixture.
The particles that strike the paper cause that die to go into solution and to be added onto paper.

g) Dosage with meter valve

Reproducibility e of disease can be determined by assay technique
Assay technique
- Accurate weighing of field container followed by dispensing of several dosages.
- Containers are reweighted and difference in weight divided by the number of dosage dispensed gives average dose.

Evaluation of Packaging components of Aerosol

I. Protection

II. Compatibility

III. Safety

I. Protection

A light-resistant container that proposed to offer protection from light was evaluated by performing the Light transmission test.
Water Vapor Permeation test, the capability of a container closure system to protect against transmission of moisture could be evaluated.