Anne J. Lexmond

Devices and formulations for pulmonary vaccination

Introduction: Pulmonary vaccination could be a promising alternative to vaccination by injection. Administration of a vaccine to the lungs does not require the use of needles, which reduces the number of trained healthcare workers needed, the risk of needle-stick injuries and needle waste. Besides a systemic immune response, pulmonary vaccination may also induce a mucosal immune response. Such a local response may increase the effectiveness of vaccination against airborne pathogens. Although this route of administration has been studied for decades, no pulmonary vaccine is commercially available yet, due to various challenges mostly intrinsic to pulmonary drug delivery and vaccine formulation. Areas covered: This review discusses the inhalation devices and formulation strategies that may be suitable for the pulmonary administration of vaccines. In addition, critical parameters are addressed, such as the target population, to help assessing whether pulmonary administration of a specific vaccine may be feasible and beneficial or not. Expert opinion: A combined approach of inhalation device and vaccine formulation development is essential. This should result in a system that can effectively be used by the target population and can be produced at low costs. Only then, this challenging administration route can be successfully applied to large-scale vaccination programs.

New Mechanisms to Explain the Effects of Added Lactose Fines on the Dispersion Performance of Adhesive Mixtures for Inhalation

Fine excipient particles or ‘fines’ have been shown to improve the dispersion performance of carrier-based formulations for dry powder inhalation. Mechanistic formulation studies have focussed mainly on explaining this positive effect. Previous studies have shown that higher drug contents may cause a decrease in dispersion performance, and there is no reason why this should not be true for fines with a similar shape, size and cohesiveness as drug particles. Therefore, the effects on drug detachment of ‘fine lactose fines’ (FLF, X50 = 1.95 µm) with a similar size and shape as micronised budesonide were studied and compared to those of ‘coarse lactose fines’ (CLF, X50 = 3.94 µm). Furthermore, interactions with the inhalation flow rate, the drug content and the mixing order were taken into account. The observed effects of FLF are comparable to drug content effects in that the detached drug fraction was decreased at low drug content and low flow rates but increased at higher flow rates. At high drug content the effects of added FLF were negligible. In contrast, CLF resulted in higher detached drug fractions at all flow rates and drug contents. The results from this study suggest that the effects of fines may be explained by two new mechanisms in addition to those previously proposed. Firstly, fines below a certain size may increase the effectiveness of press-on forces or cause the formation of strongly coherent fine particle networks on the carrier surface containing the drug particles. Secondly, when coarse enough, fines may prevent the formation of, or disrupt such fine particle networks, possibly through a lowering of their tensile strength. It is recommended that future mechanistic studies are based on the recognition that added fines may have any effect on dispersion performance, which is determined by the formulation and dispersion conditions.

Effect of inhaler design variables on paediatric use of dry powder inhalers

Age appropriateness is a major concern of pulmonary delivery devices, in particular of dry powder inhalers (DPIs), since their performance strongly depends on the inspiratory flow manoeuvre of the patient. Previous research on the use of DPIs by children focused mostly on specific DPIs or single inspiratory parameters. In this study, we investigated the requirements for a paediatric DPI more broadly using an instrumented test inhaler. Our primary aim was to assess the impact of airflow resistance on children’s inspiratory flow profiles. Additionally, we investigated children’s preferences for airflow resistance and mouthpiece design and how these relate to what may be most suitable for them. We tested 98 children (aged 4.7–12.6 years), of whom 91 were able to perform one or more correct inhalations through the test inhaler. We recorded flow profiles at five airflow resistances ranging from 0.025 to 0.055 kPa0.5.min.L−1 and computed various inspiratory flow parameters from these recordings. A sinuscope was used to observe any obstructions in the oral cavity during inhalation. 256 flow profiles were included for analysis. We found that both airflow resistance and the children’s characteristics affect the inspiratory parameters. Our data suggest that a medium-high resistance is both suitable for and well appreciated by children aged 5–12 years. High incidences (up to 90%) of obstructions were found, which may restrict the use of DPIs by children. However, an oblong mouthpiece that was preferred the most appeared to positively affect the passageway through the oral cavity. To accommodate children from the age of 5 years onwards, a DPI should deliver a sufficiently high fine particle dose within an inhaled volume of 0.5 L and at a peak inspiratory flow rate of 25–40 L.min−1. We recommend taking these requirements into account for future paediatric inhaler development.

Prerequisites for a dry powder inhaler for children with cystic fibrosis

Correct inhalation technique is essential for effective use of dry powder inhalers (DPIs), as their effectiveness largely depends on the patient’s inhalation manoeuvre. Children are an especially challenging target population for DPI development due to the large variability in understanding and inspiratory capacities. We previously performed a study in which we determined the prerequisites for a paediatric DPI in a mostly healthy paediatric population, for which we used an empty test inhaler with variable internal airflow resistance and mouthpiece. In the current study we investigated what specifications are required for a DPI for children with cystic fibrosis (CF), for which we expanded on our previous findings. We recorded flow profiles of 35 children with CF (aged 4.7–14.7 years) at three airflow resistances (0.031–0.045 kPa0.5.min.L-1) from which various inspiratory parameters were computed. Obstructions in the mouth during inhalation were recorded with a sinuscope. All children were able to perform a correct inhalation manoeuvre, although video analysis showed that children did not place the inhaler correctly in the mouth in 17% of the cases. No effect was found of medium to high airflow resistance on total inhaled volume, which implies that the whole resistance range tested is suitable for children with CF aged 4–14 years. No effect could be established of either mouthpiece design or airflow resistance on the occurrence of obstructions in the mouth cavity. This study confirms our previous conclusion that the development of DPIs specifically for children is highly desired. Such a paediatric DPI should function well at 0.5 L inhaled volume and a peak inspiratory flow rate of 20 to 30 L/min, depending on the internal airflow resistance. This resistance can be increased up to 0.045 kPa0.5.min.L-1 (medium-high) to reduce oropharyngeal deposition. A higher resistance may be less favourable due to its compromising effect on PIF and thereby on the energy available for powder dispersion.

Realising the potential of various inhaled airway challenge agents through improved delivery to the lungs

Inhaled airway challenges provoke bronchoconstriction in susceptible subjects and are a pivotal tool in the diagnosis and monitoring of obstructive lung diseases, both in the clinic and in the development of new respiratory medicines. This article reviews the main challenge agents that are in use today (methacholine, mannitol, adenosine, allergens, endotoxin) and emphasises the importance of controlling how these agents are administered. There is a danger that the optimal value of these challenge agents may not be realised due to suboptimal inhaled delivery; thus considerations for effective and reproducible challenge delivery are provided. This article seeks to increase awareness of the importance of precise delivery of inhaled agents used to challenge the airways for diagnosis and research, and is intended as a stepping stone towards much-needed standardisation and harmonisation in the administration of inhaled airway challenge agents.

Targeting the small airways with dry powder adenosine: a challenging concept

ABSTRACT Background: Small-particle inhaled corticosteroids (ICS) provide a higher small airway deposition than large-particle ICS. However, we are still not able to identify asthma patients who will profit most from small-particle treatment. Objective: We aimed to identify these patients by selectively challenging the small and large airways. We hypothesized that the airways could be challenged selectively using small- and large-particle adenosine, both inhaled at a high and a low flow rate. Design: In this cross-over study 11 asthma subjects performed four dry powder adenosine tests, with either small (MMAD 2.7 µm) or large (MMAD 6.0 µm) particles, inhaled once with a low flow rate (30 l min–1) and once with a high flow rate (60 l min–1). Spirometry and impulse oscillometry were performed after every bronchoprovocation step. We assumed that FEV1 reflects the large airways, and FEF25–75%, R5-R20 and X5 reflect the small airways. Results: The four adenosine tests were not significantly different with respect to the threshold values of FEV1 (p = 0.12), FEF25–75% (p = 0.37), R5-R20 (p = 0.60) or X5 (p = 0.46). Both small- and large-particle adenosine induced a response in the small airways in the majority of the tests. Conclusions: In contrast to our hypothesis, all four adenosine tests provoked a response in the small airways and we could not identify different large- or small-airway responders. Interestingly, even the test with large particles and a high flow rate induced a small-airway response, suggesting that selective challenging of the small airways is not necessary. Future studies should investigate the relation between particle deposition and the site of an airway response.

Drug Delivery Devices for Inhaled Medicines.

Historically, the inhaled route has been used for the delivery of locally-acting drugs for the treatment of respiratory conditions, such as asthma, COPD, and airway infections. Targeted delivery of substances to the lungs has some key advantages over systemic administration, including a more rapid onset of action, an increased therapeutic effect, and, depending on the agent inhaled, reduced systemic side effects since the required local concentration in the lungs can be obtained with a lower dose. Fortunately, when designed properly, inhaled drug delivery devices can be very effective and safe for getting active agents directly to their site of action.