Aerosol

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ABCP |PHARMA BLASTERSZ...
 Aerosols are dosage forms containing therapeutically active
ingredients that are packaged under pressure in a sealed container
and are released as a fine mist of spray upon activation of a
suitable valve system
 An aerosol is a suspension of fine solid particles or liquid droplets
in a gas.
 NATURAL AIROSOLS: clouds, fog and smoke.
 Pharmaceutical aerosol is a suspension of fine solid drug particles
or liquid drug droplets in a carrier gas/propellant.
 Also known as Inhalational Drug Delivery systems (IDDS) or
inhalants as drug is inhaled through nose / mouth to the lungs.
 Commonly used for respiratory disease (asthma) and lung disease
(emphysema).
 They are intended for local action in the nasal / throat area, and
systemic action also when drugs are absorbed from the lungs in to
the blood stream.

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 •ALL PHARMACEUTICAL AEROSOLS ARE NOT
INHALATIONAL.
E.g Topical aerosol sprays: Local anesthetics, pain reliever spay.
TYPES;
 Aerosols are of two types, the two-phase system consisting of gas
and liquid or the three-phase system consisting of gas, liquid and
solid or liquid.
 The two-phase aerosol comprises a solution of active ingredient(s)
in liquefied propellant and the vaporised propellant.
 The solvent is usually the propellant or a mixture of the propellant
and co-solvents such as ethanol, propylene glycol and polyethylene
glycols.
 The three-phase aerosol consists of a suspension or emulsion of the
active ingredient(s) and the vaporised propellants.
 In the suspension the ingredient(s) may be dispersed in the
propellant system with the aid of suitable pharmaceutical aids such
as wetting agents, solubilising agents, emulsifying agents,
suspending agents and lubricating agents to prevent clogging of
valves.
 Foam aerosols contain an emulsion of the active ingredient(s),
surface-active agents, aqueous or non-aqueous liquids and the
propellants.
 Active ingredients: For satisfactory bioavailability the active
ingredient(s) should have the majority of particles under 10mm in
size in the case of inhalation aerosols and not more than
100 mm for other types of aerosols.

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ADVANTAGES OF AEROSOL:
 Drug is delivered directly to the target organ (lung),
 Less dose required so less systemic exposure so less toxic.
 Fast action, no decomposition of drug.
 Aerosol doses are generally smaller than systemic doses; for
example: oral albuterol is 2 to 4 mg; inhaled albuterol is 0.2 mg
 Systemic side effects are less frequent and severe with inhalation
compared to systemic delivery (injection, oral).
 Onset of effect with inhaled drugs is faster than with oral dosing;
eg, oral albuterol is ≤ 30 min; inhaled albuterol is ~ 5 min.

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 Since the drugs are absorbed directly into the blood stream via the
lungs, there is no decomposition or loss of drug in the
gastrointestinal tract such as occurs when the drug is administered
orally.
 Since the medication is sealed in a container, there is no danger of
contamination of the product with foreign materials.
DISADVANTAGES OF AEROSOL
 Loss of Drugs: 10-20% drugs goes to lungs.
 The remaining drug is lost in the device, the exhaled breath, the
oropharynx, and the environment.
 Reasons of drug loss or dose variability
 •The number and variability of device types confuses patients and
clinicians.
 •Lack of standardized technical information on inhalers for
clinicians.
 Lack of knowledge of correct or optimal use of aerosol devices by
patients and clinicians.
 Difficulty in coordinating hand action and inhalation with MDIs.
 Correct breathing pattern, is difficult.
 NOTE: Drug loss may lead to dose variability.

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 Lung deposition is 10-20% for most aerosol systems.
COMPONENTS OF AEROSOL PACKAGE
 Propellant.
 Drug Product Concentrates
 Container.
 Valve and actuator.
Propellant ;
 Propellants: Propellants perform the essential function of expelling
the material from the container by supplying the necessary
pressure within the aerosol system.
 They are liquefied or compounded gases having vapour pressures
exceeding atmospheric pressure.
 The commonly used propellants in aerosol systems are
hydrocarbons, especially the fluorochloro-derivatives of methane
and ethane, the butanes and pentanes and compressed gases such
as nitrogen and carbon dioxide. Mixtures of propellants are often
employed to obtain the necessary delivery and spray characteristics
of the aerosol.
 Propellants are chemicals with a vapor pressure greater than
atmospheric pressure at a temperature of 40˚C.

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 It is one of the most important components of the aerosol package
(It is said to be the heart of the aerosol).
 It also serves as a solvent for certain active ingredient.
 It provides the necessary force to expel the contents; it causes the
product to be dispensed as foam or mist/spray, depending on the
formulation and the type of valve employed.
1 COMPRESSED GAS
 Compressed gas propellants really only occupy the head space
above the liquid product in the can.
 When the aerosol valve is opened the gas 'pushes' the liquid out of
the can.
 The amount of gas in headspace remains the same but it has more
pressure space, and as a result the drop during the life of the can.
 Eg ; Carbon dioxide , Nitrous oxide , Nitrogen .

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2 LIQUIFIED GAS
 As the product is used up, some of the liquid propellant turns to
gas and keeps the head space full of gas, pressure in the can
remains essentially constant and the spray performance is
maintained throughout the life of the aerosol.
 Hydrocarbons: as (LPG) liquefied petroleum gas
(eg. propane, butane, & isobutane)
Halocarbons: (CFC) chloro fluro carbon
Trichloro-monofluoro-methane (propellant 11)
Dichloro-difluoro-methane (propellant 12)
Dichloro-tetrafluoro-ethane (propellant 114)

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IDEAL PROPERTIES FOR PROPELLANT
1 Hydrocarbon propellants ;
•Most common
•Cheap,
•Good solvent
•Doesn't have any environmental problems (no ozone depletion).
•Bad taste,
•Flammable
2 Chlorofluorocarbons ;
•Most common
•Cheap,
•Good solvent
•Environmental problems (depletes ozone layer)
•FDA banned use of CFC
3 Hydrofluorocarbons (HFA) ;
•Replaced CFC
•No Environmental problems (does not depletes ozone layer).
•Very costly.
Drug Product Concentrates;
 Based on the drug product formulation as solution, emulsion,
suspension or powder we can have Solutions aerosol, emulsion
aerosol or Suspensions aerosols .

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 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
Container ;
 Aerosol containers are made of metal (stainless steel, aluminium or
tin-plated steel), glass or plastic or a combination of these
materials.
 The containers must be so designed that they provide the
maximum in pressure safety and impact resistance.

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VALVES ;
 The valve regulates the flow of the active ingredient(s) and
propellant from the container and determines the spray
characteristics of the aerosol.
 It must be manufactured from materials which are inert to the
contents of the aerosol. The commonly used materials are rubber,
plastic, aluminium and stainless steel.
 For topical products valves capable of providing continuous spray
operation are suitable.
 However, products for oral or nasal inhalation require metered-
dose valves which ensure delivery of a uniform quantity of spray
and an accurate dose of the active ingredient(s), both within
specified tolerances, with each activation of the valve.
 Metered valves may need priming before use if the aerosol
packages have not been stored properly or have not been used for
long periods of time
Container
Material
Maximum
Pressure
(psig)
Temp
(F)
Uncoated glass 18 70
Coated glass <25 70
Plastic <25 70
Aluminum 180 130
Stainless Steel 180 130
Tin-plated steel 180 130

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Aerosol valve is multifunctional in that
•It is capable of being easily opened and closed.
•It regulate the flow of product concentrate.
•It regulate the amount of emitted material.
•It is capable of delivering the content in the desired form (mist spray, or
foam).
•Mist is a phenomenon of small droplets suspended in air.
•A spray is a dynamic collection of drops dispersed in a gas.
•The process of forming a spray is known as atomization/nebulization.
1. Continuous Spray valve is the most common used valve.
2. Metering valves are used to accurately deliver a dose of
medication. applicable to the dispensing of potent medication.
These operate on the principle of a chamber whose size determines
the amount of medication dispensed.
3. Foam valves have only one orifice that leads to a single expansion
chamber of appropriate volume to allow the product concentrate to
expand into a ball of foam.

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Actuator.
 The actuator or adaptor which is fitted to the aerosol valve stem is
a device which on depression or other movement opens the valve
and directs the spray to the desired area.
 The design of the actuator which incorporates an orifice of varying
size and shape and expansion chamber is very important in
influencing the physical characteristics of the spray or foam,
particularly in the case of inhalation aerosols, where the active
ingredient(s) must be delivered in the proper particle size range.
 A proportion of the active ingredient(s) is usually deposited on the
inner surface of the actuator; the amount available is therefore less
than the amount released by actuation of the valve

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 A specially designed button to activate the valve assembly.
 The actuator allows for easy opening and closing of the valve and
is an integral part of almost every aerosol package.
 It is actuator design and dimensions that determine the physical
form of the emitted product concentrate (spray or foam).
Actuators types:
1.Spray.
2.Foam. (Large orifices)
3.Solid stream. (Large opining – as ointment)
4.Special applications. (They are designed to deliver the medication to
the appropriate site of action - throat, nose, eye, or vaginal tract).

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VARIOUS ACTUATORS AND APPLICATORS

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MANUFACTURE OF PHARMACEUTICAL AEROSOLS
Preparation of aerosols:
 Aerosols are commonly prepared by filling under pressure and
sometimes by filling after refrigeration to temperatures below 0o
.
 In filling under pressure, the requisite volume of the concentrate of
the active ingredient(s) is filled in the container and either the
propellant is forced under pressure through the valve orifice after
the valve is sealed, or the propellant is allowed to flow under the
valve cap and the valve assembly is sealed.
 In either case, the air in the container must be evacuated by means
of vacuum or displacement with a small amount of the propellant.
 Aerosol products should be manufactured under strictly controlled
conditions and subjected to process controls which include
propellant and medicament fill weights, pressure test and leak test
of the finished product.
 Inhalation aerosols should be manufactured in conditions designed
to minimise microbial and particulate contamination.
Two methods are used to manufacture aerosols
COLD FILL PROCESS and the PRESSURE FILL PROCESS
1 COLD FILL PROCESS
•In the cold fill process, both the product concentrate and the propellant
must be cooled to temperatures below 0°C where they will remain
liquefied.

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•The chilled product concentrate is quantitatively added to the equally
cold aerosol container and then the liquefied gas is added.
•The heavy vapors of the cold liquid propellant will generally displace
the air present in the container.
•When filling is complete, the valve assembly is inserted into the
container and crimped into place.
•The container is then passed through a water bath of about 55°C to
check for leaks or distortion in the container.
•The cold fill process takes advantage of the property that some
ingredients will liquefy when cooled.
•Aqueous solutions cannot be filled by this process since the water will
turn to ice in the low temperatures.
2 PRESSURE FILL PROCESS: ( more common than cold filling )
•Pressure filling is carried out essentially at room temperature.
•The product concentrate is placed in the container, the valve assembly
is inserted and crimped into place.
•Then the liquefied gas, under pressure, is added through the valve.
•The entrapped air in the package might be ignored if it does not
interfere with the stability of the product, or it may be evacuated prior to
filling or during filling.
•After the filling operation is complete, the valve is tested for proper
function.
•It has the advantage that there is less danger of moisture contamination
of the product and also less propellant is lost in the process.

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TYPES OF AEROSOLS INHALATION DELIVERY
SYSTEMS
•There are currently two main types of aerosol generating devices.
1-Inhalers
2-Nebulizers
Inhalers;
•Inhalers are portable, handheld devices that are available in two types:
 Metered dose inhalers (MDI)
 Dry Powder Inhaler DPI.
 Metered dose inhalers (MDI
•MDI are the most commonly prescribed. These devices push out a
pre-measured spray of medicine. When the person squeezes the inhaler,
a measured "puff" of medicine is released.
ADVANTAGES:
Short treatment time,
Reproducible dose emitted.
DISADVANTAGES:
•Fixed drug concentrations
•Failure to shake can alter drug dose causing variability
•Limited range of drugs
•Hand–breathing coordination is difficult for many patients

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•Proper inhalation pattern (slow inspiration to total lung capacity) and
breath-hold can be difficult
Dry Powder Inhalers ;
•DPIs are bolus drug delivery devices that contain solid drug, suspended
in a dry powder mix that is fluidized when the patient inhales.
•In dry powder inhaler (DPI) systems, drug is inhaled as cloud of fine
particles.
•The drug is either preload in an inhalation device or filled into hard
gelatin capsules or foil blister disc which are loaded into a device prior
to use.
ADVANTAGES:
•DPI formulations are propellant free and do not contain any excipient
hence environmental sustainability.
•Little or no patient coordination required.
•Formulation stability.
•DPIs can also deliver larger drug doses than MDIs.
DISADVANTAGES:
•DPIs are generally less efficient at drug delivery than MDIs, such that
twice the dose is usually required for delivery from a DPIs than from the
equivalent MDI.
•Deposition efficiency dependent on patient’s inspiratory airflow.
•Development and manufacture more complex/expensive.
•Potential for dose uniformity problems.

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NEBULIZERS:
Distinctly different from both pMDIs and DPIs, in that the drug is
dissolved or suspended in a polar liquid, usually water.
•Used for drugs that cannot be conveniently formulated into MDIs or
DPIs, or where the therapeutic dose is too large.
•Nebulizers are electric- or battery-powered machines that turn liquid
drugs into a fine mist that's inhaled into the lungs. The user breathes in
the mist through a mouthpiece or facemask.
•Nebulizers are used mostly in hospital and ambulatory care settings and
are not typically used for chronic-disease management because they are
larger and less convenient, and the aerosol is delivered continuously
over an extended period of time.
ADVANTAGES:
 Nebulizers deliver relatively large volumes of drug.
 Drug concentrations can be modified.
 Normal breathing patterns can be used.
 Useful in very young, very old, debilitated, or distressed patients
 An inspiratory pause (breath-hold) is not required for efficacy
DISADVANTAGES;
 Treatment times are lengthy for pneumatically-powered nebulizers
 Equipment required may be large and cumbersome
 Need for power source (electricity, battery, compressed gas)
 Variability in performance characteristics among different brands
 Possible contamination with inadequate cleaning
 Wet, cold spray with facemask delivery

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 Potential for drug delivery into the eyes with facemask delivery.
 It usually takes about 5 or 10 minutes to give medication by
nebulizer, and sometimes longer.
 Nebulizers can be less effective if a child is crying during use,
since less medicine will be inhaled.
Labelling:
The label states
(1) the name(s) of the active ingredient(s);
(2) the total amount of the active ingredient(s) in the except in the case
of metered-dose preparation for inhalation);
(3) that the container should be shaken before use;
(4) the other instructions for use;
(5) the date after which the preparation is not intended to be used;
(6) the conditions under which it should be stored;
(7) a warning that the container is under pressure and that it must not be
punctured, broken or incinerated even when apparently empty;
(8) the statement: "Warning. Keep away from children"
In the case of metered-dose aerosols, the label states in addition
(1) the total number of deliveries available from the container;
(2) the amount of active ingredient(s) released each time the valve is
actuated.

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The instruction leaflet includes
(1) the direction for correct use of the aerosol;
(2) a warning that the container may explode if punctured, exposed to
excessive heat or direct sunlight;
(3) the directions for the disposal of the used or partly-used container.
EVULATION;
Pressure test:
 Select not less than 5 pressurised containers, remove the caps and
covers, and immerse in a constant-temperature bath until the
internal pressure is constant at a temperature of 25o
ą 1o
.
 Remove the containers from the bath, shake well, and remove the
actuator and water, if any, from the valve system. Keep each
container in an upright position and place on the valve stem a pre-
pressurised gauge of a calibration approximating the expected
pressure and fitted with an adapter appropriate for the valve stem
dimensions. Read the pressure directly from the gauge.
Leak test:
 Select 12 pressurised containers at random, and record the date and
time to the nearest half-hour.
 Weigh each container to the nearest mg, and record the weight, in
mg, of each as W1.
 Allow the container to stand in an upright position at room
temperature for not less than 3 days, and again weigh each
container, recording the weight, in mg, of each as W2and recording
the date and time to the nearest half-hour.

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 Determine the time, T, in hours, during which the containers were
under test. Calculate the leakage rate, in mg per year, of each
container from the expression 365 x 24/T x (W1 - W2).
Partical size;
 The most important physicochemical parameter influencing the
deposition of aerosols in the lungs is particle or droplet size.
 The aerodynamic diameter is defined as the diameter of a unit-
density sphere having the same settling velocity, generally in air,
as the particle. This encompasses particle shape, density, and
physical size, all of which influence the aerodynamic behavior of
the particle.
MICROSCOPY TECHNIQUES;
 Particle Collection
 Electrostatic Precipitation
 Light Microscopy

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Application;

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Aerosol

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