Mucus hypersecretion is a clinical feature of BE. This mucus-retention aids bacterial infection that can lead to pulmonary exacerbations, which further develops the “viscous cycle” of mucus-retention, infection, inflammation and tissue damage. Mucoactive drugs target this cycle by potentially increasing the ability to expectorate sputum and/or decrease mucus hypersecretion.

The current guidelines indicate that mucoactives in combination with airway clearance may be considered to enhance sputum expectoration in BE, but the evidence to support their use is limited. Furthermore, evidence for the effectiveness of hypertonic saline (HTS) and carbocisteine is insufficient to recommend them within the management of BE. However, EMBARC/BRONCH-UK data show that BE centres do prescribe mucoactives. This is important because adherence to therapies in BE in general is low, decreases as the number of prescribed medications increases, and is also related to poorer patient outcomes, including the number of pulmonary exacerbations and quality of life. Therefore, it is essential that only those drugs that are effective should be prescribed for patients with BE. There are cost considerations associated with mucoactives, and there is a risk of polypharmacy side effects.

Unlike BE, relatively strong evidence exists to favour the use of both HTS and carbocisteine within other respiratory conditions. Therefore, this trial will answer important clinical questions about whether similar benefits can be demonstrated in BE by using a pragmatic design to explore the specific effects of mucoactive agents, and directly support, or refute, more targeted use of these drugs.

Patients will be randomised to one of four treatment groups: (i) standard care and twice daily nebulised HTS (6%), (ii) standard care and carbocisteine, (iii) standard care and combination of twice-daily nebulised HTS and carbocisteine, or (iv) standard care alone.