Therapeutic Aerosols

Dr. Basavaraj K. Nanjwade M. Pharm., Ph. D

Department of PharmaceuticsFaculty of Pharmacy

Omer Al-Mukhtar UniversityTobruk, Libya.

E-mail: nanjwadebk@gmail.com

2014/05/18 1Faculty of Pharmacy, Omer Al-Mukhtar University, Tobruk, Libya.

CONTENTS

1. Definition and uses, model of operation.2. Deposition in human respiratory tract.3. Formulation aspects, 4. Propellants.5. Packages and containers.6. Absorption and clearance.7. Applications.8. References.2014/05/18 2Faculty of Pharmacy, Omer Al-Mukhtar University,

Tobruk, Libya.

Definition and uses• Aerosols may be defined as disperse phase system, in

which very fine solid particles or liquid droplets get dispersed in the gas which acts as continuous phase.

Uses:1. The medicament can be delivered directly to the

affect area such as burnt skin and wound.2. So it minimises the discomfort caused by mechanical

or manual application

2014/05/18 3Faculty of Pharmacy, Omer Al-Mukhtar University, Tobruk, Libya.

Model of operation• Drugs are generally delivered to the respiratory tract

for the treatment or prophylaxis of airways diseases, such as bronchial asthma and cystic fibrosis.

• The administration of a drug at its site of action can result in a rapid onset of activity.

• Additionally, smaller doses can be administered locally compared to delivery by the oral or parenteral routes.

• The pulmonary route is also useful where a drug is poorly absorbed orally.

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Deposition in human respiratory tract

• Casts of the upper airways have been constructed in an attempt to predict aerosol deposition in the lungs.

• Most lung deposition models are based on the influence of particle size on aerosol deposition.

• Breathing parameters, such as breathing frequency and tidal volume, play a key role in lung deposition.

2014/05/18 5Faculty of Pharmacy, Omer Al-Mukhtar University, Tobruk, Libya.

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Site of Deposition in human

respiratory tract

Formulation aspects • The formulation of pharmaceuticals as therapeutic

aerosols is continually increasing. • Thus antiseptic materials can be sprayed onto abraded

skin with a minimum of discomfort to the patient.• One product, ethyl chloride, cools sufficiently on

expansion so that when sprayed on the skin, it freezes the tissue and produces a local anesthesia.

• This procedure is sometimes used in minor surgical operations.

2014/05/18 7Faculty of Pharmacy, Omer Al-Mukhtar University, Tobruk, Libya.

Propellants• Propellants develops a pressure in the container. • Compressed gases such as carbon dioxide or nitrogen

and liquified gases like methane or ethane can be used as propellants.

• These days propellants like trichloro-fluoro-methane, dichloro-difluoro-methane, dichloro-tetrafluoro-ethane and difluoro-ethane are used in pharmaceutical aerosols.

• The medicaments to be propelled may be solid or liquid.

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Packages 1. They are used for spray bandages and for application

of drugs meant for topical use.2. They are used for spray administration of drugs into

various body cavities.3. They are used for administration of drugs such as

local anesthetics, local antiseptic, local analgesics and anti-inflammatory drugs.

4. They are used to spray cosmetics preparations such as perfumes.

5. They are used to spray disinfectants, deodorizers and air sanitizers.

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Containers• The containers are made from metal, glass and plastic.• Pharmaceutical aerosols may be packaged in tinplated

steel, plastic-coated glass or aluminium containers.• MDIs (Metered-Dose Inhalers) are generally presented

in aluminium canisters, produced by extrusion to give seamless containers with a capacity of 10-30 mL.

• Aluminium containers with an internal coating of a chemically resistant organic material, such as an epoxy resin, can be used.

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Container

Absorption• Hydrophilic materials are poorly absorbed through

membrane pores at rates inversely proporational to molecular size.

• Some drugs, such as sodium cromoglycate, are partly absorbed by a saturable active transport mechanism.

• The rate of drug absorption, and consequently drug action, can be influenced by the formulation.

• Prolonged absorption may be achieved using suspension formulations or novel drug delivery systems such as liposomes and microspheres.

2014/05/18 12Faculty of Pharmacy, Omer Al-Mukhtar University, Tobruk, Libya.

Clearance• Particles deposited in the ciliated conducting airways

are cleared within 24 hours and ultimately swallowed. • Insoluble particles penetrating to the alveolar regions,

and which are not solubilized in situ, are removed more slowly.

• Alveolar macrophages engulf such particles and may then migrate to the bottom of the mucociliary escalator, or alternatively particles may be removed via the lymphatics.

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Applications

1. The use of aerosols as a dosage form is particularly important in the administration of drugs via the respiratory system.

2. In addition to local effects, systemic effects may be obtained if the drug is absorbed into the bloodstream from the lungs.

3. Topical preparations are also well suited for presentation as aerosols.

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THANK YOUe-mail: nanjwadebk@gmail.com

2014/05/18 15Faculty of Pharmacy, Omer Al-Mukhtar University, Tobruk, Libya.