What is refractory chronic cough?

Chronic cough is a cough lasting more than eight weeks. Many people with chronic cough have an identifiable underlying cause: acid reflux, postnasal drip from rhinitis or sinus disease, asthma, eosinophilic bronchitis, side effects from ACE inhibitor blood-pressure medicines, smoking, or environmental exposures. When the underlying cause is identified and treated, the cough usually resolves.

Refractory chronic cough is the term for a chronic cough that persists despite identifying and addressing all the usual causes. Some patients have unexplained chronic cough where no underlying cause can be found at all. In both cases, the cough itself appears to have become the central problem; the cough reflex becomes hypersensitive and is triggered by stimuli that would not normally cause cough in other people.

The biology. Modern understanding is that the cough reflex involves nerve fibres in the airways that detect potentially harmful stimuli and trigger cough. In refractory chronic cough, these nerve fibres become abnormally sensitive, possibly through changes in receptors and ion channels including a type called P2X3. Treating the cough hypersensitivity directly is the basis of the new targeted therapy.

The traditional therapy. Once underlying causes have been addressed, options have been limited. Speech and language therapy can help patients reduce cough through behavioural techniques. Off-label medicines (gabapentin, low-dose morphine, others) have been used with mixed evidence.

The modern targeted therapy. Gefapixant blocks P2X3 receptors and reduces cough frequency in patients with refractory chronic cough. The medicine has approval in some jurisdictions and is in active commercial use. Follow-on P2X3 antagonists and other mechanism-targeted medicines are in late-stage trials. The expectation is that refractory chronic cough will increasingly become a category with multiple targeted options rather than the bare category it has been.

What to expect. If you have had a cough for more than eight weeks, it is worth working through the typical causes systematically. If a clear cause is found, treating it usually resolves the cough. If no cause is found or treatment of identified causes does not help, the term refractory chronic cough applies and targeted therapy options are increasingly available.