Chapter 15: Medicines optimization: ensuring quality and safety
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Pulmonary administration
Definition
Pulmonary administration involves dosage forms that enter the body via the lungs in aerosol form with the aim of achieving local effects, such as improving bronchodilation or improving clearance of pulmonary secretions (Chernecky et al. [39], Perry [281]). Systemic effects can also be achieved through the pulmonary route, for example via volatile anaesthetics (Hillery et al. [128]). Some are inhaled via the mouth, some via the nose, and some via the nose and mouth (Downie et al. [82]).
Related theory
In order for drugs to reach the lungs, they must be delivered in an aerosol form. The aerosol penetrates the lung airways, the deeper passages of the respiratory tract provide a large surface area for drug absorption, and the alveolar–capillary network absorbs medication rapidly (Potter and Perry [289]).
There are three ways in which an aerosol form can be produced: by nebulizer, by pressurized metered dose inhalers and by drug powder inhalers:
- Nebulization involves the passage of air or oxygen driven through a solution of a drug. The resulting fine mist is then inhaled via a face‐mask (Trounce and Gould [354]). Some antibiotics and bronchodilators may be given in this way (Figure 15.12).
- Metered dose inhalers (MDIs) involve a drug being suspended in a propellant in a small hand‐held aerosol can in the form of a spray, mist or fine powder. Metered doses can then be delivered from the aerosol by the use of a metering valve within the device, which is designed to release a fixed volume, for example of salbutamol. Steroid medications are often administered by MDI to treat long‐term reactive airway disease (Chernecky et al. [39], Perry [281]) (Figure 15.13).
- Dry powder inhalers involve a powder being delivered to the lungs via a breath‐actuated device. Examples of inhalers in this group are the Accuhaler (Figure 15.14) and the Turbohaler (Figure 15.15).
Figure 15.12 Nebulizer.
Figure 15.13 Metered dose inhaler (MDI).
Figure 15.14 Accuhaler.
Figure 15.15 Turbohaler.
Pre‐procedural considerations
Equipment
Nebulizer
The advantage of nebulizers is that they can deliver drugs to the lungs consistently with better deposition in greater amounts, if necessary, than standard inhalers because of the smaller particles that are generated. They also do not require any co‐ordination in order to deliver the drug to the lungs. Nebulization can also be used to deliver drugs where the dose is large or needs to be dispersed in a large volume. The disadvantages are that they are expensive, they are not easily portable and the delivery of the drug can be difficult to control, for example due to loss in the tubing and mouthpiece.
Solutions and suspensions for nebulization may be available in single‐dose units or multiple‐dose containers. Careful measurement is required in the case of the latter. Some products are presented as dry powders that require reconstitution, while some solutions require dilution before administration. The manufacturer's instructions should be followed to ensure that the drug is properly dispersed and at the appropriate concentration for nebulization.
Metered dose inhaler
The advantages of MDIs are that they are convenient, can deliver a fixed dose and are inexpensive. The disadvantage can be the co‐ordination needed to use one. In order for the MDI to be effective, the patient needs to trigger it during a deep, slow inhalation and then hold their breath for around 10 seconds. This need for co‐ordination between actuation of the dose and inhalation can be removed by using a spacer device (Figure 15.16). The spacer device reduces the speed with which the dose is delivered and the resulting ‘cold freon’ effect that can occur, which can prevent a patient from continuing to inhale after actuation of the MDI. Spacers are also useful for patients on high‐dose inhaled steroids in order to prevent oral candidiasis, for children and patients requiring higher doses, and can improve dose delivery to 15% (Downie et al. [82]). Spacer devices are designed to be compatible with specific inhalers and therefore care should be taken to ensure the correct spacer device is used.
Figure 15.16 Spacer device.
Medication in MDIs is under pressure and so they should not be punctured or stored near heat or in hot conditions (e.g. patients must be informed not to leave their MDI in a hot car) (Chernecky et al. [39]).
Dry powder inhalers
Dry powder inhalers are also useful when there are problems with co‐ordination. However, they can initiate a cough reflex and patients need to have sufficient breath inhalation to activate the device. It is also important to remember that because these medications are absorbed rapidly through the pulmonary circulation, most create systemic side‐effects (Chernecky et al. [39], Perry [281]).
There are multiple types and brands of device available, including a number of combination products. Care must be taken in product selection, and the current recommendation is to keep patients on inhaler devices from the same range (BTS and SIGN 2016).
Specific patient preparation
Patients who suffer from chronic respiratory disease and require airway management frequently receive inhalation medications. Maximum benefit is obtained only when the correct technique of inhalation is used so it is vital that patients are taught how to use these devices correctly and safely. Placebo inhalers and devices are available for educating patients on the use of their inhalers. Periodic checks should be carried out to ensure that efficiency is being maintained.
Use of an MDI requires co‐ordination during the breathing cycle, and impairment of grasp or presence of tremors of the hands interferes with patients’ ability to depress the canister within the inhaler (Chernecky et al. [39], Perry [281]). Studies have shown that both adults and children have difficulties with aerosol inhalers; problems include co‐ordinating activation and inhalation, too rapid inhalation and too short breaths after inspiration (Hilton [129]). Baseline observations of pulse, respirations and breath sounds should be performed before beginning treatment to use as a comparison during and after treatment (Potter and Perry [289]). Patients who are to receive nebulized medicines should be in a sitting position either in bed or in a chair (Downie et al. [82]).
Education
Compliance is more likely to be achieved if the patient is well informed. It is the responsibility of the nurse, doctor and pharmacist to ensure that patients have adequate teaching and demonstration and are monitored at intervals. The patient should know the following:
- about the disease, the purpose of the therapy, and how to recognize and report deterioration in their condition
- how to use and care for the inhaler
- the dose to be taken
- the time interval
- the maximum number of inhalations that should be taken in 24 hours (Downie et al. [82]).
Procedure guideline 15.6
Medication: administration by inhalation using a metered dose or dry powder inhaler
Procedure guideline 15.7
Medication: administration by inhalation using a nebulizer
Post‐procedural considerations
If the nebulizer is marked as single use then it must be discarded after use. However, nebulizers should not be treated as single use unless clearly indicated by the manufacturer. If they can be reused, then the nebulizer chamber and mask should be washed in hot soapy water, rinsed thoroughly and dried with paper towels to reduce bacterial contamination and also to prevent any build‐up of crystallized medication in the nebulizer (Downie et al. [82]). Spacer devices should be washed, rinsed and allowed to dry naturally on a weekly basis and replaced after 6–12 months (Downie et al. [82]).
Complications
There is a risk of patients developing oral candidiasis when using a corticosteroid MDI or dry powder inhaler. This can be reduced by using a spacer device for an MDI and encouraging the patient to rinse their mouth after administration.
Overuse of some inhalers can result in cardiac dysrhythmias and patients may suffer from tachycardia, palpitations, headache, restlessness and insomnia. The doctor should be informed and observations commenced (Potter and Perry [289]).
