Introduction.
An inhaler is a medical device used for delivering medicines into the lungs through the work of a person's breathing.
This allows medicines to be delivered to and absorbed in the lungs, which provides the ability for targeted medical treatment to this specific region of the body, as well as a reduction in the side effects of oral medications.
There are a wide variety of inhalers, and they are commonly used to treat numerous medical conditions with asthma and chronic obstructive pulmonary disease being among the most notable.
1. Dry power inhalers:
The dry-powder inhalers are made to deliver powdered medications and excipients to the lungs.
Dry powder inhalers (DPIs) are devices through which a dry powder formulation of an active drug is delivered for local or systemic effect via the pulmonary route.
Dry powder inhalers are bolus drug delivery devices that contain solid drug, suspended or dissolved in a nonpolar volatile propellant or in dry powder inhaler that is fluidized when the patient inhales.
These are frequently used to treat respiratory conditions like asthma, bronchitis, emphysema, and COPD. They have also been used to treat diabetes mellitus.
The dry powder platform includes devices that produce an aerosol directly from 1 to 5 µm drug powder or excipient mixtures.
Excipients in DPI are used as carriers for Active Pharmaceutical Ingredients (API), with Lactose Monohydrate being the most commonly used carrier.
Formulation of DPI mainly includes following three steps;
API Production.
Formulation of API with or without carriers.
Integration of the formulation into devices.
API Production:
In the case of DPI, the most important API requirement is particle size. The drug particle size should be less than 5 µm. It should be in the range of 2-5 μm.
There are various sort of mills used for size reduction of drugs but few of them are appropriate for DPI to reduce the size in the range of 2-5 μm such as fluid-energy mills, such as the jet mill; high-peripheral-speed mills, such as the pin-mill; and the ball mill.
Formulation of API with or without carriers:
The carrier in DPI improves the flow property of powder as well as the aerosol performance of cohesive drugs and fine lactose.
After the drug and carrier (s) have been brought to their desired forms separately, they are combined in the blending process.
Integration of the formulation into device;
After blending, the formulation is filled into capsules, multi-dose blisters, or reservoirs for use with the inhaler device.
The filling process is automated and is determined by the metering system.
The primary inhaler parts are the same for all devices on the market and many that are in development.
The Dry Powder Inhaler device is made up of the following components: powder formulation, dose measuring system, powder de-agglomeration principle, and mouthpiece.
There are two types:
Unit dose devices:
The drug is formulated as a micronized drug powder and carrier system in a single-unit dose device and supplied in individual gelatin capsules, which are then embedded into the device for a single dose.
Multi dose Devices:
The multi-unit dose device employs factory metered and sealed doses that are packaged in such a way that the device can hold multiple doses without needing to be reloaded.
Typically, the packaging consists of replaceable disks or cartridges, or strips of foil/polymer blister packaging that can or cannot be reloaded.
2) Formulation of Pressurized Metered Dose Inhalers:
A metered-dose inhaler (MDI) is a device that delivers a specific amount of medication to the lungs in the form of an aerosolized medicine burst that the patient inhales.
It is the most widely used method of treatment for asthma, chronic obstructive pulmonary disease (COPD), and other respiratory diseases.
For the treatment of asthma and COPD, the medication in a metered dose inhaler is typically a bronchodilator, corticosteroid, or a combination of both.
Pressurized metered aerosols may be formulated as either solutions or suspensions of drug in the liquefied propellant.
MDIs can be formulated with the drug completely dissolved in the formulation, rendering a solution formulation, or with the drug practically insoluble in the formulation, rendering a suspension formulation.
Compared with suspension formulations, solution MDIs offer the benefits of homogenous formulation (i.e., patients do not need to shake the vial immediately prior to use and there is no concern related to sampling homogeneity), a finer residual aerosol.
When formulating solution MDIs, the total amount of fine particle drug delivered cannot simply be increased by increasing the drug concentration in a formulation.
Many drugs are not readily soluble in HFA (Hydrofluoroalkane) propellants, which frequently limits the amount of drug that can be dosed using MDIs.
Previously, surfactants or complexation aids were used in MDIs to increase drug solubility in CFC (chlorofluorocarbon) systems .However, many of the conventional excipients used in CFC formulations and approved for human use, are insoluble in HFA system.
However, it should be noted that CFCs pose significant environmental risks because they are known to deplete the ozone layer.
Containers, propellants, and metering valves are the essential ingredients for the formulation of MDIs.
Filling a Metered Dose Inhaler Canister: The canister is filled by liquefying the propellant at low or high pressure. Cold filling involves chilling and filling active compounds, excipients, and propellant at temperatures around -60℃. The canister is then sealed with the valve and additional propellant is added at the same temperature.
A drug/propellant concentrate is produced and filled at nearly room temperature and pressure (in fact, it is usually slightly chilled to below 20℃). The value is crimped on to the canister and additional propellant is filled at elevated pressure through the valve, in a process known as gassing.
Pressure filling is most frequently employed for inhalation aerosols.
3) Nebulizers:
A device converts liquids into aerosols that can be inhaled into the lower respiratory tract.
Nebulizers used in aerosol drug delivery produce a poly-disperse aerosol with drug particles ranging in size from 1 to 5 µm in diameter.
Most nebulizers atomize using compressed air, but some use ultrasonic energy.
In general, nebulizers are used to treat cystic fibrosis, asthma, COPD, and other respiratory diseases or disorders.
There are three types of nebulizers available on the market.
Jet Nebulizer.
Ultrasonic Nebulizer.
Mesh Nebulizer.
Jet Nebulizer:
This method employs compressed gas to create an aerosol (tiny medication particles in the air).
Jet nebulizers are useful for the acute and domiciliary treatment of a variety of respiratory diseases, as well as pediatric and adult medical practices.
These nebulizers required 2-10 L/min withdrawal medication from the reservoir via a capillary tube.
It may produce a broader range of particles, which are blasted into one or more baffles (to convert larger particles to smaller particles) and returned to the nebulizer.
Ultrasonic Nebulizer:
This makes an aerosol through high-frequency vibrations.
The particles are larger than with a jet nebulizer.
Ultrasonic nebulizers incorporate a piezoelectric crystal vibrating at high frequencies (1-3 MHz) to produce an aerosol.
Ultrasonic nebulizers work on the principle that converts electrical energy to high frequency vibrations using a transducer.
This nebulizer generates vibrations, which are transferred to solution surface that would create waves, and those waves produce aerosol;
These are large volume nebulizers to deliver hypertonic saline for sputum inductions.
Mesh Nebulizer:
Mesh nebulizers contain apertures or aperture plates; when we apply force, it will generate aerosol.
They force liquid medications through multiple apertures in a mesh or aperture plate to generate aerosol.
Mesh nebulizers are more efficient than jet nebulizers and can provide higher drug doses to patients.
The efficiency of mesh nebulizers is affected by various factors like size of the pore, aerosol chamber, and reservoir.
Formulating Nebulizer Fluids:
Water is used to make nebulizer fluids, with the addition of co-solvents such as ethanol or propylene glycol on occasion, and surfactants for suspension formulations.
Because hypo-osmotic and hyper-osmotic solutions, as well as high hydrogen ion concentrations, can cause bronchoconstriction, iso-osmotic solutions with a PH greater than 5 are typically used.
Antioxidants and preservatives may also be included as stabilizers, but these may also cause bronchospasm, so sulfites in particular are generally avoided as antioxidants in such formulations.
While most nebulizer formulations are solutions, nebulizers can also deliver micronized drug suspensions.
In general, ultrasonic nebulizers deliver suspensions poorly, whereas jet nebulizers deliver drugs more efficiently as the size of the suspended drug decreases, with little or no particle release when particles exceed the droplet size of the nebulizer aerosol.
Commonly Asked Questions.
Describe in detail formulation of the inhalers along with their different types.
Write a short note on,
Jet Nebulizer.
Ultrasonic Nebulizer.
Mesh Nebulizer.
Nebulizer Fluids.