(5) Pulmonary Drug Delivery Systems

PULMONARY DRUG DELIVERY SYSTEMS

definition

• Drug delivery into lungs via respiratory tract

• NOT nasal/local — must reach lungs

PULMONARY DRUG DELIVERY SYSTEMS

 KEY CONCEPT

• Lungs = upside-down tree

  • Trachea → bronchi → bronchioles → alveoli

👉 Important for drug deposition

TYPES OF PULMONARY DELIVERY - overview

1. Therapeutic Gases

2. Aerosols

3. Device-Based Systems

TYPES OF PULMONARY DELIVERY

Therapeutic Gases - examples

Anesthesia (halothane, desflurane)

TYPES OF PULMONARY DELIVERY

Aerosols - definition

Solid/liquid particles dispersed in gas

TYPES OF PULMONARY DELIVERY

Aerosols - fun facts

• Most common pulmonary system

• Used since 1950s

• Future depends on propellants

TYPES OF PULMONARY DELIVERY

device based systems:

Type	Key Feature

Type	Key Feature
MDI	Fixed dose
Nebulizer	Continuous delivery
DPI	Powder inhalation

 CRITICAL: MDI vs Nebulizer

Feature	MDI	Nebulizer
Dose	Fixed	Continuous
Control	High	Low
Output	One puff	Continuous mist

NEBULIZER TYPES

• Air jet → high velocity air

• Ultrasonic → vibrating crystal

• Vibrating mesh → mesh system

ADVANTAGES

• Fast onset

• Direct lung delivery

• Avoid first-pass metabolism

• Large surface area + blood supply

• Can replace injections

 DISADVANTAGES

• Expensive

• Cooling irritation (propellant evaporation)

• Cardiotoxicity (fluorinated HC)

AEROSOL SYSTEM

Components

1. Product concentrate

2. Propellant

3. Container

4. Valve system

AEROSOL SYSTEM

 Product Concentrate

• Contains:

• Drug

• Antioxidants

• Surfactants

• Solvents

AEROSOL SYSTEM

 Propellant

• Heart of aerosol

AEROSOL SYSTEM

 Propellant - Functions:

• Provides pressure

• Determines spray/foam

• Acts as solvent

HOW AEROSOL WORKS

1. Propellant exists as:

   • Liquid + vapor (equilibrium)

2. Press valve →

   • Pressure pushes liquid up tube

3. Release →

   • Propellant evaporates

4. Drug becomes:

   • Droplets or particles

5. System re-equilibrates

👉 Pressure stays constant until empty

REFRIGERATION EFFECT

• Rapid evaporation → cooling

• Can cause irritation

PROPELLANT TYPES

Type	Examples	Key Points
Fluorinated HC	Propellant 11, 12	Non-toxic, ozone issue
Hydrocarbons	Propane, butane	Cheap, flammable
Compressed gas	N₂, CO₂	Low pressure

VAPOR PRESSURE - what 2 laws?

Dalton’s Law

Raoult’s Law

Dalton’s Law

Total pressure = sum of partial pressures

Raoult’s Law

Partial pressure = mole fraction × pure vapor pressure

Used when mixing propellants

CONTAINERS

• Must withstand:

140–180 psi at 103°F

CONTAINERS

Types:

• Metal

• Glass

• Plastic