The Pharmaceutics and Compounding Laboratory
Intranasal Preparations

Administration Devices

Sprays, MDIs, Aerosols

Intranasal inhalations are administered to achieve either local respiratory or systemic therapeutic benefits. Special devices, such as the plastic spray bottle or bottles with metered dose valves, are used to break up a solution preparation into small particles and deliver a spray.

Some active drugs are administered using pressurized intranasal aerosols (i.e., an intranasal aerosol inhaler). The advantages and disadvantages of the intranasal aerosols are the same as those of the inhaled aerosols administered through the mouth.

The one-way nasal pumps (i.e., MDIs in bottles) prevent drawback contamination of nasal fluids into the bottle after administration.

 

Nebules

Other drugs are packaged in nebules and administered tbrough nebulizers as "inhalation therapy." The nebulizers dispense the drug particles into the 0.5-5.0 µm range, which is the optimum particle size for inhalation administration. The particles in the optimum particle size range are carried out of the nebulizer in a mist; the larger particles do not exit the device, but fall back into the reservoir of medication to be re-nebulized.

Inhalers

If the drug is sufficiently volatile, it can be administered via a nasal inhaler. The inhaler is a capped cylindrical tube that contains fibrous material impregnated with a volatile drug. The patient removes the cap and the inhaler tip is placed just inside the nostril. As the patient inhales, air is pulled through the tube and the vaporized drug is pulled into the nasal cavity.

Loss of Drug During Administration

Even through there are several different dosing devices for intranasal administration, the drug can still be lost following administration by three mechanisms:

  • Metabolism in the nasal mucosa. The nasal mucosa is an enzymatically active tissue; some drugs are significantly degraded when administered by this route.
  • Mucus flow and ciliary movement. The normal physiology of the nasal cavity is to move mucus and inhaled contaminants up and away from the lungs and toward the orifice of the nose. Some drug loss will occur as the drug is swept outward by these processes.
  • Swallowing. Intranasal administration can also cause the drug to be swallowed and in some cases enough drug will be swallowed to be equal to an oral dose. This may lead to a systemic effect from the drug even though it is intranasally administered.