- Valves
- Actuators
- Types of aerosols system
• VALVES :- A valve must be capable of delivering the content in desired form and amount. There are two forms of valves
1. Continuous spray valve
2. Metering valve
• Continuous spray valve :- It is used mainly tropical aerosols. It is consists of different parts
1. Ferrule or mounting cap :- It is used to connect valve to container. It is consists of aluminium and brass. Epoxy coating must be done to protect the corrosion.
2. Valve body or housing :- It is manufactured from nylon or delrin. Its opening is 0.013 inch to 0.08 inch. It is attached with dip tube.
3. Stem :- It is made of nylone or delrin and sometimes used of brass or stainless steel.
4. Gasket :- It is made of Buna-N & Neoprene rubber.
5. Spring :- It is hold the gasket its proper place.
6. Dip tube :- It is made up of polyethylene or poly propylene which are more rigid. Dip tube of the commonly opening is 0.120 inch to 0.125 inch. Inner diameter is 0.050 inch & when highly viscous product it is 0.195 inch.
• Metering valves :- It is used for dispensing of potent medication. Operates on the principle of a chamber whose size determines the amount of medication dispensed . Approximately 50 to 150 mg ± 10 % of liquid materials can be dispensed at one time with the use of such valves.
Actuators :- These are specially designed buttons which helps in delivering the drug in desired form. Types of actuators :-
1. Spray actuators :- Topical preparation
2. Foam actuators :- consists of large orifice 0.070-0.125 inch .
3. Solid –stream actuator :- used for semi solid preparation.
4. Special actuator :- It delivers the medicaments appropriate site of action such as throat, nose , eye etc.
• Aerosols devices (depending of physical state):-
1. Metered dose inhalers :- Medication for lung, asthma treatment, COPD and other respiratory devices. It is consists of three parts :-
• Canister
• Metering valve
• actuator
2. Dry powder inhalers :- Delivered dry powder.
3. Nebuliser :- Nebulisers use oxygen compressed air or ultrasonic power to break up medical solution and suspensions into small aerosols droplets called mists.
• Types of aerosols system :-
1. Solution system :- It is also referred as two phase system and consists of vapour and liquid phase. 5% propellant in foams and 95 % inhalation product.
2. Water based system :- Relatively large amount of water can be used to replace all or part of non aqueous solvent used in aerosols. Ethanol is used as a co solvent to increase the solubility of propellant in water. Recently developed aqueous system which allows the dispersing of a fine mist or spray of APIs dissolved in water which is not possible with usually three phase system.
3. Suspension or dispersion system :- Such a system involve a dispersion of APIs in proper land or mixture of propellants. To decrease rate of settling of dispersed particle various surfactant or suspending agents are used. This system is used for oral or inhalation aerosols.
4. Foam system :- The liquid propellant is emulsified and is generally found in internal phase. There are type aqueous stable foam, non-aqueous stable foam, quick breaking foam, thermal foam.
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