Nebulizers convert liquid medication into a mist for inhalation, making them effective for delivering solutions, suspensions, or other formulations to the lungs.
Formulation Considerations
Drug Solubility:
Must be soluble in an aqueous vehicle for uniform dosing.
Particle/Droplet Size:
Optimal size: 1–5 µm for deep lung deposition.
pH and Isotonicity:
pH: Near physiological levels to avoid irritation.
Isotonicity: Maintains osmotic balance and prevents bronchoconstriction.
Preservatives and Stabilizers:
Prevent microbial contamination and stabilize the drug.
Surfactants:
Modify surface tension, influencing droplet size and delivery.
Viscosity Modifiers:
Adjust aerosol properties without hindering nebulizer function.
Buffering Agents:
Maintain pH for stability and minimize irritation.
Compatibility with Nebulizer Type:
Tailor formulations to jet, ultrasonic, or vibrating mesh nebulizers.
Stability:
Ensure the drug remains stable without precipitation or degradation.
Driving Gas:
Oxygen, air, or heliox may influence drug delivery.
Types of Nebulizers
1) Jet Nebulizers:
Use compressed air to create mist.
Durable, suitable for high-viscosity solutions, but larger and noisier.
2) Ultrasonic Nebulizers:
High-frequency waves generate mist.
Quieter, portable, but may heat formulations, affecting heat-sensitive drugs.
3) Vibrating Mesh Nebulizers:
Use a vibrating mesh or plate to create mist.
Quiet, efficient, portable, with consistent particle size.
4) Soft Mist Inhalers (SMIs):
Generate mist without external power.
Portable and easy to inhale, with slow-moving mist.