COMPONENTS FOR AEROSOL FORMULATION

Presented by- Moriyom Akhter

World University of Bangladesh

Aerosols Aerosol are the products that depend on the power

of a compressed or liquefied gas to expel the contents from the container. Aerosols are termed also pressurized package.

Pharmaceutical aerosols:

Aerosol products containing therapeutically active ingredients dissolved, suspended or emulsified in a propellant or a mixture of solvent and propellant and intended for topical administration, for administration into one of the body cavities (ear, rectum and vagina) or intended for administration orally or nasally as fine solid particles or liquid mists through the pulmonary airways, nasal passages or oral cavity.

Aerosol

Components of aerosols:

Propellant

Container

Valve and actuator

Product concentrate

A propellant is a chemical with a vapor pressure greater than atmospheric pressure at 40°C (105°F).

PROPELLANTS

Function:

1) It is responsible for developing the vapor pressure within the container

2) Expel the product when the valve is opened and in the atomization or foam production of the product.

3) When the propellant is a liquefied gas or a mixture of liquefied gases, it can also serve as the solvent or vehicle for the product concentrate.

Types:1. Compressed Gas Propellants Inert gases

Carbon DioxideNitrous OxideNitrogen

2. Liquefied gas propellants

Hydrocarbons(HC)

Liquefied Petroleum Gases(Propane, Isobutane, n-Butane) Isopentane, n-Pentane.

Chloroflourocarbon (CFC)

Trichloro-mono-flouromethane (11), Di-chloro-diflouro-methane (12) , Di-chloro-tetra-flouro-methane (114)

Fluorinated hydrocarbons(FHC)

1,1 Diflouroethane (152a)

Ethers Dimethyl ether

PropellantsCompressed Gas Propellants Gases such as nitrogen, nitrous oxide, and carbon dioxide have been used

as aerosol propellants for products dispensed as fine mists, foams, or semisolids. Compressed gas propellants only occupy the head space above the liquid in the can.  When the aerosol valve is opened the gas 'pushes' the liquid out of the can. The amount of gas in the headspace remains the same but it has more space, and as a result the pressure will drop during the life of the can.

Liquefied gas Liquefied propellants are gases that exist as liquids under pressure.

 Because the aerosol is under pressure the propellant exists mainly as a liquid, but it will also be in the head space as a gas.  As the product is used up as the valve is opened, some of the liquid propellant turns to gas and keeps the head space full of gas. 

Compressed gas propellants

Advantages Low inhalation toxicity High chemical stability High purity Inexpensive No environmental problem

Disadvantages Require use of a nonvolatile

co-solvent Produce course droplet sprays Pressure falls during use

Liquefied gas propellants

Hydrocarbons It is mainly used for the preparation of topical preparation, chemically

stable, no hydrolysis, Inflammable , low toxicity. They are lighter than water.Chlorofluorocarbon (CFC) propellants

P-11, P-12, and P-114 are the CFCs of

choice for oral, nasal,

and inhalation aerosols.

Advantages  Low inhalation toxicity High chemical stability High purity CFC-11 is a good solvent

Liquefied gas propellantsHydrochlorofluorocarbons (HCFC) and Hydrofluorocarbons (HFC)

The hydrochlorofluorocarbons (HCFC) and hydrofluorocarbons (HFC) differ from CFCs in that they may not contain chlorine and have one or more hydrogen atoms. P-22, 142b, and 152a are used in topical pharmaceuticals. These three propellants have a greater miscibility with water and therefore are more useful as solvents. They are also slightly more flammable than the other propellants.

Ether Di Methyl Ether - This is an alternative liquefied propellant, and is more

common in personal care products, and some air fresheners. DME is significantly higher in price than hydrocarbon propellants. Classified as a flammable gas. It is a very strong and aggressive solvent. An advantage of DME is its solubility in and compatibility with aqueous formulas.

  Disadvantage of DME is that in aqueous formulas at levels at or above 19%,

the DME will attack the can lining thus requiring a corrosion inhibitor.   

Formulation :Contains two essential components: Product concentrate : contains ingredients or mixture of active

ingredients and other such as solvents, antioxidants and surfactants.

Propellant : Propellant May be single or blend of various propellants

The type of the system

selected depends on many

factors such as Physical, chemical and

pharmacological properties

of active ingredients Site of application

Formulation Depending on the type of aerosol system utilized, the pharmaceutical

aerosol may be dispensed as a fine mist, wet spray, quick-breaking foam , stable foam, semisolid or solid.

Type of systems are 1. Solution system : Consist of a solution of active ingredients in pure propellant or

a mixture of propellant and solvents. Easy to formulate, provided that the ingredients are soluble in

the propellantAerosol solutions have been used To make foot preparations Local anesthetics Spray on protective films Anti-inflammatory preparations and Aerosols for oral and nasal applications

2. Suspension or Dispersion systems

Active ingredients are suspended or dispersed throughout the propellant or propellant and solvent phase.

Anti-asthmatic drugs, steroids, and antibiotics are delivered as suspension aerosols. When the valve is actuated, the suspension formulation is emitted as an aerosol and the propellant rapidly vaporizes and leaves a fine dispersion of the product concentrate.

There are some problem arise for suspension aerosols that are include agglomeration, particle size growth, valve clogging, moisture content, and particle size of the dispersed aerosolized particles.

To overcome these problems: lubricants: isopropyl myristate , oleic acid Provide slippage between particles Lubricate components parts of the valve Surfactants: to disperse particles

3.Water based system ( Emulsion, dispersion ):

Relatively large amounts of water can be used to replace all part or part of the non aqueous solvents used in aerosol. These products are generally referred to as water-based aerosols and depending on the formulation are emitted as a spray or foam. To produce a spray the formulation must consist of a dispersion of active ingredients and the solvents in an emulsion system in which the propellants is external phase. In this way when the product is dispensed, the propellants vaporizes and disperses the active ingredients into many particles. Since propellant and water are not miscible a three phase forms (propellants phase, water phase and vapor phase) are used. To increase the solubility of propellants in water, ethyl alcohol can be added to the system. Ethanol has been used as a co solvent to solubilize some of the propellant in the water.

4. Foam system: Foams are produced when the product concentrate is dispersed

throughout the propellant and the propellant is in the internal phase; i.e., the emulsion behaves like o/w emulsion.

Aqueous stable foams-The techniques used in preparing an aerosol emulsion are the same as those used for non aerosol emulsions. This is generally used for steroid antibiotics.

Non-aqueous stable foams-Various medicinal agents can be formulated by this way.

Quick breaking foams-These type of system is specially applicable to medication, which can be applied to limited or to large areas without the use of mechanical force to dispense the active ingredients. Quick breaking foams aerosol may be formulated by ethyl alcohol, surfactant, water and hydrocarbon propellant.

Thermal foams - These are used when the warmness is required.

5. Intranasal aerosol: Drug delivery systems intended for the deposition of the

medication into the nasal passageways has long been used as a most effective, means of administering drugs intended to produce either a local action of systemic effect.

The Intranasal aerosol offers numerous disadvantage including the delivery of a measured dose of drug , excellent depth of penetration into the nasal passageways with minimal intervertent penetration into lungs, reduce droplet of particle size , lower dosage than a comparable system preparation maintenance of sterility from dose to dose.

The modes of administering of intranasal preparations have been limited to nasal drops, non-pressurized nasal sprays (mist), inhalants, intranasal gel, creams, ointments.

Wherever the medicament is needed, there the product can be delivered in the required form like foam, spray etc.

It have rapid onset of action. It will act on targeted area without any contamination.

In conclusion, aerosol dosage form is a dosage form with an easy administration. It’s main advantage is it requires lesser amount of active ingredients or medicaments.

THANK YOU