Aerosols _ ICRI , Bangalore , India

7/30/2019 Aerosols _ ICRI , Bangalore , India

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Aerosols

Vijayalakshmi


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Definition

Pressurized dosage forms that upon

actuation emit a fine dispersion of liquid or

solid material containing one or more active

ingredients in a gaseous medium

Aerosols expel their contents as fine mist,

coarse, wet or dry spray, a steady steam or astable or a fast breaking foam

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Advantages

Uncontaminated delivery of a portion of drug

Hermetic containers--- protected from oxygen

Opaque containers ----- protected from

atmospheric light

Sterility due to aseptic packing

Topical application feasible

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Advantages

Particle size of the emitted product and its

physical form may be controlled

Dosage can be controlled through the use of

metered valves

Aerosol application is a clean process

requiring little or no wash up by the user

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Principle

Formulation consists of two component parts

Product concentrate

Propellant

Product concentrate is active ingredient

Combined with antioxidants , surface active

agents and solvents

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Principle

Propellant is a liquefied gas or a mixture ofliquefied gases

Responsible for maintaining pressure

Acts as solvent or vehicle for the productconcentrate

Compressed gases like carbondioxide,nitrogen,nitrous oxide are employed aspropellants

Chloro-fluorocarbons were used aspropellants

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Propellants

Eg:dichloro-difluoro methane, dichloro

tetrafluoro ethane, trichloromonofluoro

methane

Fluorinated hydrocarbons are gases at roomtemperature but can be liquefied by cooling

or by compression at room temp.

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Aerosol systems

Pressure and performance

Pressure can be controlled by

Type and amount of propellant

Nature and amount of product concentrate

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Types

Solution system

Two phase system vapor phase and liquid

phase

Active ingredients are soluble in the propellant

Water based system

Water replaces the non aqueous solvents

Depending on the formulation emitted as spray orfoam.

Surfactants, cosolvents are used

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Types

Suspension or disperse systems

Foam systems

Non aqueous stable foams

Quick breaking foams

Thermal foams

Intranasal foams

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Selection of a propellant

Blends of various LG propellants

Non reactive with formulation ingredients orvalve components

Eg:trichloromonofluoro methane tends to formhydrochloric acid with water or ethyl alcohol

No physiological effects

Non irritant

No effect on the absorption of drugs

No cardiotoxic effects

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Two phase systems

Contains liquid phase containing propellant

and product concentrate

Vapor phase

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Three phase systems

Three phases consisting of

Immiscible liquid propellant

Highly aqueous product concentrate

Vapor phase

Dip tube extends only up to product

concentrate (aqueous phase)

Vapor phase is replenished from thepropellant

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Compressed Gas systems

Pressure of the compressed gas in the head

space of the container forces the product

concentrate up the diptube and out of the

valve Nitrogen is the inert gas that can be used

Other gases that can be used are

carbondioxide, nitrous oxide Pressure decreases as the product is used

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Aerosol container and valve assembly

Proper combination of formulation, containerand valve assembly.

Formulation must not chemically interact with

the container or valve components Container and valve must be capable of

withstanding the pressure

Resist corrosion

Valve must contribute to the form of theproduct

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Containers

Glass, uncoated or plastic coated

Metal including tin plated steel, aluminum andstainless steel

Plastics Selection :

Adaptability to production methods

Compatibility with formulation components Sustainability to pressure

Design and aesthetic appeal

cost

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Glass containers

Disadvantage:

Brittleness and danger for breakage

Properly designed to sustain pressure

Advantages

Chemical compatibility

More adaptive

Plastic coated glass containers are used

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Tin plated steel containers

Most widely used metal containers

Starting material is in sheets

Completed aerosol cylinders are seamed and

soldered to provide a sealed unit

Corrosion and leak test perfomed

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Aluminum containers

Manufactured by methods that make them

seamless

Greater safety against leakage,

incompatibility and corrosion

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Stainless steel

Certain small volume containers

Corrosion resistant

Main limitation is higher cost

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Plastic containers

Vapor permeates within the container

Drug plastic interactions

Affect the release of the drug

Reduce the efficacy of product

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Valve assembly

Function :To permit expulsion of the contents of the can

In the desired form ,

At the desired rate and

In the metered dose in the proper amount ofdose

Materials used in the manufacture of valvesmust be

Inert to the formulations Approved by FDA

Plastic ,rubber, aluminum and stainless steel

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Valve assembly

Actuator

Stem

Gasket

Spring

Mounting cap

Housing

Dip tube

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Actuator

The button the user presses to activate the

valve assembly for the emission of the

product

Permits easy opening and closing of thevalve

Product is discharged from the orifice

Type and quantity of propellant used controlthe particle size

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Stem

Supports the actuator

Delivers the formulation in the proper form to the

chamber of the actuator

Gasket

Placed closely with the stem Prevents leakage of the formulation when the

valve is closed

Spring Holds gasket in place

Helps in returning valve to the closed position

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Mounting cap

Attached to the aerosol can or container

Holds the gasket in place Inner part is in contact with the formulation

Housing

Is directly below the mounting cap

Links the dip tube and the stem and actuator Dip tube

Extends from housing down into the product

Brings the formulation from the container to the valve

Diameter of the tube depends on the viscosity of theproduct and intended delivery

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Materials used

Actuator ,stem ,housing and dip tube ---

plastic

Mounting cup and spring --- metal

Gasket --- rubber or plastic resistant to

formulation.

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Metered dose inhalers

Used when the formulation is a potent

medication

Amount of material discharged is regulated

by an auxiliary valve chamber

Single depression of the actuator causes

evacuation of this chamber and delivery of its

contents Controlled by dual valve mechanism

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Metered dose inhalers

Actuator valve closed , chamber is sealed from theatmosphere

In this position chamber is filled with the contents ofthe chamber

Depression of the actuator causes simultaneousreversal of positions

Chamber becomes open to the atmosphere

Release its contents

Becomes sealed from the contents of the container

Upon release of the actuator system is restored forthe next dose

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Filling operations

Cold filling

Both propellant and product concentrate are

cooled to -30 to -40 degrees F

Water systems cannot be filled

Pressure filling

Product concentrate is quantitatively placed in

aerosol container

Liquified gas under pressure is metered into the

valve stem from a pressure burette

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Testing the filled containers

Leak test

Valve functioning

Valve discharge rate

Spray pattern for particle size distribution of

the spray

Accuracy and reproducibility of dosage in

metered valves

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Documents

Aerosols _ ICRI , Bangalore , India