The adaptation of e-cigarettes as drug delivery devices holds great potential for inhalation therapy. So, can we apply the advances made in nicotine delivery to other active substances?
Inhalation therapy is used to treat patients with both acute and chronic respiratory diseases, including asthma, chronic obstructive pulmonary disease (COPD), cystic fibrosis, and more. Respiratory disease is a huge global issue – an estimated 328 million people suffer from COPD globally, with many cases undiagnosed.1 WHO reports COPD as the third leading cause of death worldwide; 3.23 million in 2019, which was 6% of total deaths globally. According to WHO, asthma affected an estimated 262 million people globally in 2019 and caused 455,500 deaths.
Both of these conditions are primarily treated with inhalation therapy. For the treatment of asthma, patients typically inhale bronchodilators and antiinflammatory agents. Whereas with COPD, treatment generally is via the inhalation of bronchodilators, steroids, and antibiotics.
Overall, inhalation therapy brings several benefits over tablets and capsules. There is the obvious advantage of target organ delivery for afflictions of the throat, lungs, and oesophagus. However, inhalation therapy can also have distinct advantages for other conditions, although not delivered directly to the target organ. The delivery of therapies into the alveolar spaces of the lung results in the rapid absorption of oxygenated blood.
This allows the active substance to reach the target organ quickly and relatively intact. In comparison, intravenous injections rely on the delivery of the substance into de-oxygenated blood, which first requires passage around the body: through the heart, lungs, and then to the target organ. This relative delay can result in significant metabolism of the active substance before it reaches the target organ. Through inhalation, efficacy can be achieved with a lower dose, potentially reducing the risk of side effects and adverse events.
The deposition of the active substance is essential in achieving efficacy. The correct administration of an inhaled drug to the patient depends on several factors related to the drug’s formulation, device design, and patient use. For the treatment of lung disease, aerosol droplets must be of a size where they are not deposited on the back of the throat or in the bifurcations of the bronchi. This ensures that as much of the active substance is delivered to the alveoli as possible. In contrast, to treat a disease related to the throat or oesophagus, the particle size should be larger, to ensure deposition in the upper airway limiting the dose delivered to the lung.
Current Inhalation TechnologyInhalation therapy is traditionally performed by four types of devices: pressurised metered dose inhalers (pMDI), soft mist inhalers (SMI), dry powder inhalers (DPI), and nebulisers.
Many different inhaler devices and medications are available to treat asthma and COPD, with over 230 drug delivery system combinations available. Despite this, disease controls in clinical practice are often unsatisfactory, where a key determining factor is the match or mismatch of an inhalation device with the needs of an individual patient.2 The choice of inhaler device is essential, and can significantly impact the effectiveness of the treatment.