Inhalation Preparations

Inhalation dosage forms are intended to deliver drugs to the lungs. The lungs have a large surface area and a rich blood supply to the alveolar epithelium both of which favor rapid absorption. However, there is considerable variability in the absorption of drugs from the lungs so that this route is not considered an alternative to intravenous administration. Drugs administered via this route are to affect pulmonary function or treat allergic symptoms. Examples of drugs administered by inhalation include adrenocorticoid steroids (e.g., beclomethasone), bronchodilators (e.g., isoproterenol, metaproterenol, albuterol), and antiallergics (e.g., cromolyn).

Administrating drugs via this route is dependent on factors which involve the formulation, the administration device, and the anatomy of the lungs.

Inhalation formulations are generally solutions, suspensions, and powders. These formulations are administered via an aerosol or a dry powder inhaler. Aerosols are devices where liquid or suspension droplets are the internal phase and a gas is the external phase. Commercial aerosols are typically metered dose inhalers (MDI) that deliver a fixed dose in a spray with each actuation of the device. For compounded inhalation solutions, atomizers, nebulizers, and vaporizers are the aerosol devices.

Atomizers (right) are devices that break up a liquid into a aerosol. A squeeze bulb is used to blow air into the device. The air causes the drug solution to rise in a small dip tube and vaporizes the liquid in the air stream. To produce even smaller droplets, the air stream is directed into a baffle or bead which breaks the droplets as they collide with the device. The air and liquid then exit the atomizer.

A nebulizer (left) contains an atomizing unit within a chamber. When the rubber bulb is depressed, the medication solutions is drawn up a dip tube and aerosolized by the passing air stream. Baffles or beads may also be present in the chamber. The fine droplets exit the nebulizer. The larger droplets collect on the chamber and fall back into the reservoir where they can be used again.

Vaporizers produce a fine mist of steam. Volatile medication is added to the water in the vaporizer or to a special medication cup present in some models. The medication volatilizes and is inhaled by the patient as they breath.

Commercially available dry powder inhalers contain their dry powders in manufactured cartridges or disks. When the patient administers a dose, the device is first activated by some mechanical motion and the dry powder becomes ready for inspiration. Then the patient inhales through the device mouthpiece and the powder is drawn into the pulmonary tract along with the inspired air. These devices have overcome a major problem of inhalation therapy, synchronizing deep inspiration with the administration of the drug. Some of these devices are Diskhaler®, Turbuhaler®, Diskus®, and Rotahaler®.

Compounded powders are administered with insufflators or puffers. Squeezing the rubber bulb of an insufflator causes a turbulence within the powder reservoir which forces some of the powder into the air stream and out of the device. A puffer is a plastic accordion-shaped container with a spout on one end. The powder is placed inside the container and the puffer is actuated by squeezing the device. A portion of the powder is ejected from the spout. Beside their use in inhalation therapy, insufflators and puffers can be used to apply powdered drugs to the nose, ear, tooth socket, or body surfaces.

Regardless of the formulation or the administration device, inhalation therapy also depends on the coordination, the breathing patterns, and the respiration depth of the patient at the time of administration. Inhalation devices produce either liquid droplets or powder particles upon actuation. There is a strong correlation between the inspired particle size and its final deposition inside the lungs. Large particles (about 20 microns) impact in the back of the mouth and throat and are eventually swallowed rather than inhaled. Particles from 1 to 10 microns reach the terminal bronchioles and are more available for local therapy. Smaller particles (0.6 micron) penetrate to the alveolar sacs where absorption is most rapid, but retention is minimal since a large fraction of the dose is exhaled. The particles that reach the alveolar sacs and remain there are responsible for providing systemic effects.

Commercially Available Dry Powder Devices

Instructions for Diskhaler®:

Using the Diskhaler®:

1. Raise the lid up as far as it will go — this will pierce the blister pack
2. Close the lid.
3. Breathe out as far as is comfortable being careful not to breathe into the device.
4. Close your lips around the mouthpiece, making sure not to cover the air holes at the sides of the mouthpiece.
5. Tilt head back slightly and inhale in deeply and forcefully through the device. Remove the device from mouth.
6. Hold breath for about 10 seconds and breathe out slowly.
7. Sometimes 2 or 3 forceful inhalations are needed to make sure that all the medication is taken.
8. If a second dose is prescribed, advance the cartridge to the next number and repeat above steps.

Loading a dose:

1. Remove the cover and cartridge unit.
2. Place a disk on the wheel with the numbers facing up and slide the unit back into the Rotadisk.
3. Gently push the cartridge in and out until the number 4 appears in the window.

Instructions for Turbuhaler®

Using the Turbuhaler®:

1. Hold the device upright.
2. Breathe out with a normal breath. Do not breathe into the inhaler device. Do not shake the inhaler after loading it.
3. Close your lips around the mouthpiece.
4. Tilt your head back slightly and take a quick, full breath in. (Holding this breath for a count of 10 is not in the official documentation, however, it may be recommended). Remove the device from mouth.
5. If more than one dose is required, repeat the above steps for loading/using.
6. Place the cover back on the inhaler and twist shut. Rinse mouth with water (do not swallow).

Loading a dose:

1. Hold device upright.
2. Twist the cover and lift off.
3. Twist the brown grip fully to the right as far as it will go.
4. Twist the brown grip back again fully to the left (Listen for a clicking sound).

Instructions for Diskus®

Using the Diskus®:

1. Holding the device level and away from the mouth, breathe out as far as is comfortable being careful not to breathe into the device.
2. Close your lips around the mouthpiece.
3. Breathe in steadily and deeply through the device.
4. Remove device from mouth.
5. Hold breath for about 10 seconds and breathe out slowly.
6. To close the device, put your thumb on the thumbgrip and slide the thumbgrip back towards you as far as it will go. The device will click shut, the level will return to the original position and will reset.

Loading a dose:

1. Hold the device in one hand and put the thumb of the other hand on the thumbgrip. Push your thumb away from you as far as it will go until the mouthpiece appears and snaps into position.
2. Hold the device on a level horizontal position with the mouthpiece towards you. Slide the lever away from you as far as it will go until it clicks. Do this only one time/dose to prevent wasting of medication.

Instructions for Rotahaler®

Using the Rotahaler®:

1. Breathe out with a normal breath. Do not breathe into the inhaler device.
2. Close your lips around the mouthpiece.
3. Tilt your head back slightly and take a quick, full breath.
4. Remove the inhaler from your mouth, and hold your breath while you count to 10.
5. Repeat steps 2 through 4 if powder remains in device.
6. Wait one minute if additional dose is needed before repeating all steps.

Loading a dose:

1. Hold the device upright with the hole for the capsule facing up.
2. Twist the lower barrel of the device, as far as possible in either direction.
3. Place a capsule into the hole, making sure the colored end is up.
4. Hold the device horizontally. Twist the lower barrel back as far as possible in the opposite direction. This twisting separates the capsule and the device is now ready for use.