Pharmacotherapeutic Options for Chronic Refractory Cough

Characterization of Codeine Treatment Responders Among Patients with Refractory or Unexplained Chronic Cough: A Prospective Real-World Cohort Study

PURPOSE

Codeine is a narcotic antitussive often considered for managing patients with refractory or unexplained chronic cough. This study aimed to evaluate the proportion and characteristics of patients who responded to codeine treatment in real-world practice.

METHODS

Data from the Korean Chronic Cough Registry, a multicenter prospective cohort study, were analyzed. Physicians assessed the response to codeine based on the timing and degree of improvement after treatment initiation. Follow-up assessments included the Leicester Cough Questionnaire and cough severity visual analog scale at six months. In a subset of subjects, objective cough frequency was evaluated following the initiation of codeine treatment.

RESULTS

Of 305 patients, 124 (40.7%) responded to treatments based on anatomic diagnostic protocols, while 181 (59.3%) remained unexplained or refractory to etiological treatments. Fifty-one subjects (16.7%) were classified as codeine treatment responders (those showing a rapid and clear response), 57 (18.7%) as partial responders, and 62 (20.3%) as non-responders. Codeine responders showed rapid improvement in objective cough frequency and severity scores within a week of the treatment. At 6 months, responders showed significantly improved scores in cough scores, compared to non-responders. Several baseline parameters were associated with a more favorable treatment response, including older age, non-productive cough, and the absence of heartburn.

CONCLUSIONS

Approximately 60% of chronic cough patients in specialist clinics may require antitussive drugs. While codeine benefits some, only a limited proportion (about 20%) of patients may experience rapid and significant improvement. This underscores the urgent need for new antitussive drugs to address these unmet clinical needs.

The Severity of Chronic Cough Diary (SCCD): development and content validation of a novel patient-reported outcome instrument for evaluating the symptom experience of chronic cough

BACKGROUND

Refractory chronic cough (RCC), a cough lasting longer than 8 weeks with an unexplained underlying etiology and unresponsive to conventional treatment, can have substantial effects on patients' quality of life. For assessment of the efficacy of antitussive medication in clinical trials in RCC, patient-reported outcome (PRO) instruments should be fit for purpose with appropriate content validity. Here we describe the qualitative testing of a newly developed PRO instrument: the Severity of Chronic Cough Diary (SCCD).

METHODS

The SCCD was developed to assess patients' symptom experience of cough in patients with RCC. A preliminary version was tested and refined based on an iterative process in a qualitative study. In total, three rounds of interviews were conducted with adult participants diagnosed with RCC in the USA (n = 19) and UK (n = 10). Rounds 1-3 consisted of hybrid concept elicitation (CE) interviews and cognitive interviews (CIs), with Round 3 also including interviews in a subset of participants (n = 5) about the usability of the SCCD as administered on an electronic handheld device.

RESULTS

The CE interviews identified concepts important to patients' experiences related to RCC that were broadly in line with the concepts in the preliminary version of the SCCD. Participants provided positive feedback on the draft SCCD across all CI rounds, reporting the instrument to be relevant and straightforward to complete, and containing a comprehensive set of concepts to evaluate their symptom experience of RCC. Participants demonstrated a good understanding of proposed item wording, response options, and the 24-hour recall period, and thought completion of the SCCD on the electronic device was easy. Following revisions based on results from each interview round, the SCCD at the end of this qualitative research study had 14 items assessing the concepts of: cough symptoms (five items), symptoms related to cough (four items), disruption to activities due to cough (three items), and disruption to sleep due to cough (two items).

CONCLUSIONS

The results of this study provide qualitative evidence supporting the content validity of the SCCD as a PRO instrument for evaluating outcomes of therapies for RCC in clinical trials.

Cough and cough hypersensitivity as treatable traits of asthma

Cough is a common and troublesome symptom in people with asthma and is often associated with poorer asthma control and exacerbations. Apart from asthma, other causes or comorbidities might underlie cough in asthma, such as rhinosinusitis and bronchiectasis. Eosinophilic inflammation and bronchoconstriction can lead to an acute episode of cough or worsen chronic cough. Cough hypersensitivity with laryngeal paraesthesia, allotussia, and hypertussia might underlie the cough of asthma through augmented sensory nerve excitability of upper-airway vagal sensory nerves. Cough associated with bronchoconstriction and type 2 inflammation should respond to inhaled corticosteroids and long-acting β-adrenoceptor agonist therapy. For cough hypersensitivity in adults, speech and language therapy and neuromodulators (eg, gabapentin) could be considered. In children, there is no consistent association of asthma with cough sensitivity or between cough and asthma severity. Further research is needed to realise the potential of cough as a measure of asthma control, to understand the mechanisms of cough in asthma, and to develop safe, effective treatments and a precision-medicine approach to the management of cough in asthma in children and adults.

The P2X3 receptor antagonist filapixant in patients with refractory chronic cough: a randomized controlled trial

BACKGROUND

P2X3 receptor antagonists seem to have a promising potential for treating patients with refractory chronic cough. In this double-blind, randomized, placebo-controlled study, we investigated the efficacy, safety, and tolerability of the novel selective P2X3 receptor antagonist filapixant (BAY1902607) in patients with refractory chronic cough.

METHODS

Following a crossover design, 23 patients with refractory chronic cough (age: 60.4 ± 9.1 years) received ascending doses of filapixant in one period (20, 80, 150, and 250 mg, twice daily, 4-days-on/3-days-off) and placebo in the other. The primary efficacy endpoint was the 24-h cough frequency on Day 4 of each dosing step. Further, subjective cough severity and health-related quality of life were assessed.

RESULTS

Filapixant at doses ≥ 80 mg significantly reduced cough frequency and severity and improved cough health-related quality of life. Reductions in 24-h cough frequency over placebo ranged from 17% (80 mg dose) to 37% (250 mg dose), reductions over baseline from 23% (80 mg) to 41% (250 mg) (placebo: 6%). Reductions in cough severity ratings on a 100-mm visual analog scale ranged from 8 mm (80 mg) to 21 mm (250 mg). No serious or severe adverse events or adverse events leading to discontinuation of treatment were reported. Taste-related adverse events occurred in 4%, 13%, 43%, and 57% of patients treated with filapixant 20, 80, 150, and 250 mg, respectively, and in 12% treated with placebo.

CONCLUSIONS

Filapixant proved to be efficacious, safe, and-apart from the occurrence of taste disturbances, especially at higher dosages-well tolerated during the short therapeutic intervention. Clinical trial registration EudraCT, eudract.ema.europa.eu, 2018-000129-29; ClinicalTrials.gov, NCT03535168.

Can clinical characteristics differentiate patients with unexplained chronic cough from patients with asthma and COPD?

Background: Chronic cough is reported in up to 20% of the adult population and often persists despite medical treatment with currently available therapies. Many clinical conditions, including asthma and chronic obstructive pulmonary disease (COPD), must be excluded before making a Unexplained chronic cough diagnosis. Methods: The primary objective was to use a large hospital dataset to compare clinical features of patients with a primary diagnosis of UCC with those with asthma or COPD without a primary diagnosis of UCC to help clinicians differentiate between these conditions more readily. Data were collected for all hospitalization and outpatient medical encounters for each patient between November 2013 and December 2018. Information included demographics, encounter dates, medications prescribed at every encounter for chronic cough, lung function testing, and hematologic parameters. Asthma and COPD were combined into one group to ensure there was no overlap with UCC and due to limitations of International Classification of Diseases coding to confirm an asthma(A)/COPD diagnosis. Results: Female gender represented 70% of encounters for UCC versus 61.8% for asthma/COPD (p < 0.0001); the mean age was 56.9 years for UCC versus 50.1 years for A/COPD (p < 0.0001). The number of patients on cough medications and the cough medication frequency were significantly higher in the UCC versus A/COPD group (p < 0.0001). UCC versus A/COPD patients had a total of eight versus three cough-related encounters over the study duration (i.e., 5 years) (<0.0001). The average interval between successive encounters was less for UCC (114 days) versus the A/COPD (288 days) group. Gender-adjusted Forced expiratory volume in the first second of exhalation/Forced vital capacity (FEV₁/FVC) ratios, residual volume%, and Diffusion capacity for carbon monoxide (DLCO%) were significantly higher in UCC versus A/COPD, whereas the response to bronchodilators of FEV₁, FVC and residual volumes were significantly greater in A/COPD patients. Conclusions: Clinical characteristics differentiating UCC from A/COPD could accelerate recognition of UCC diagnosis especially in the subspecialty setting where patients with these disorders are referred.

Improvements in Objective and Subjective Measures of Chronic Cough with Gefapixant: A Pooled Phase 3 Efficacy Analysis of Predefined Subgroups

Introduction

In phase 3 trials (COUGH-1/COUGH-2), gefapixant 45 mg twice daily significantly reduced 24-h cough frequency vs placebo in refractory or unexplained chronic cough (RCC or UCC).

Methods

Here, the efficacy of gefapixant 45 mg vs placebo was evaluated across COUGH-1/COUGH-2 in predefined subgroups based on sex, region, age, cough duration, cough severity, cough frequency, and diagnosis (RCC, UCC). Awake cough frequency reductions at Week 12 and LCQ response rates (i.e., ≥ 1.3-point improvement) at Week 24 were assessed.

Results

Among 1360 participants analyzed, gefapixant 45 mg resulted in consistent awake cough frequency reductions overall and across predefined subgroups at Week 12. Gefapixant also resulted in improved LCQ scores across subgroups at Week 24; ≥ 70% of participants in each subgroup treated with gefapixant 45 mg had an LCQ response.

Conclusion

These data suggest gefapixant 45 mg provides consistent objective and subjective efficacy across subgroups of individuals with RCC or UCC.

Effectiveness of the Therapy Program for Management of Chronic Cough: Preliminary Data From a Randomized Clinical Trial

PURPOSE

The purpose of this study is to analyze the effectiveness of the Therapy Program for Management of Chronic Cough (TMCC) in laryngeal sensations and symptoms related to the cough in individuals with chronic refractory cough (CRC).

METHOD

This research is a randomized double-blind clinical trial (Register Number: RBR-4m6x29). Eleven participants were allocated to two groups by parallel randomization: The Experimental Group-consisting of six individuals who underwent the TMCC; and the Control Group-consisting of five individuals who underwent the Comprehensive Vocal Rehabilitation Program (CVRP). Two primary outcomes were analyzed: self-perception of laryngeal sensations (Newcastle Laryngeal Hypersensitivity Questionnaire [LHQ-Br]) and self-perception of symptoms of upper airway-related cough (Cough Severity Index [CSI-Br]). The two-way repeated-measures analysis of variance was used to compare the evaluation moments and intervention groups. For multiple comparisons, the Tukey test with Bonferroni correction was used. To evaluate the effect size, eta partial square was used.

RESULTS

There was no difference between groups for any outcomes analyzed. There was a statistically significant difference with a large effect size for the moment factor in all outcomes. A statistically significant difference was observed with a large effect size for the interaction effect between group and moment for LHQ-Br total and CSI-Br psychological and functional.

CONCLUSIONS

The TMCC and CVRP were effective for the rehabilitation of CRC, considering the viewpoint of the subject. The TMCC improved laryngeal sensations and psychological and functional symptoms, while CVRP was relevant to improve psychological and functional symptoms in individuals with CRC.

Effects of transcranial direct current stimulation on cough reflex and urge-to-cough in healthy young adults

Background

Chronic cough is prevalent in the clinic. The existing therapies are mostly limited to medical treatment, with poor curative effects and serious side effects. Studies have suggested that the right dorsolateral prefrontal cortex (rDLPFC) may play an active role in the inhibitory pathway of cough elicitation. Thus, this study explored the effect of transcranial direct current stimulation (tDCS) on the rDLPFC activation in relation to cough reflex and urge-to-cough sensitivity.

Methods

Twenty-three healthy young adults completed the experiment. Participants randomly received tDCS anodal stimulation, cathodal stimulation, and sham stimulation, and the interval between every two stimuli was at least one week. The tDCS (2 mA, 30 min) stimulated brain rDLPFC region. After tDCS intervention, cough reflex threshold and urge-to-cough were evaluated immediately by inhalation of citric acid-saline solution.

Results

Compared with sham stimulation, the cough reflex thresholds logC₂ and logC₅ have increased under tDCS anodal stimulation (1.78 ± 0.55 g/L vs. 1.57 ± 0.57 g/L, p < 0.05; 1.92 ± 0.53 g/L vs. 1.67 ± 0.56 g/L, p < 0.05), accompanied by the increase of the urge-to-cough threshold LogC_u (0.76 ± 0.53 g/L vs. 0.47 ± 0.44 g/L, p < 0.05). In contrast, the urge-to-cough sensitivity expressed as UTC slope was not significantly changed (1.21 ± 0.86 point·L/g vs. 1.00 ± 0.37 point·L/g, p > 0.05), and there were no apparent changes in cough reflex thresholds Log C₂ and logC₅, urge-to-cough threshold LogC_u, and urge-to-cough sensitivity UTC slope under tDCS cathodal stimulation, compared with sham stimulation.

Conclusions

This study found that anodal tDCS stimulation of rDLPFC could significantly decrease cough reflex sensitivity, accompanied by the increase of urge-to-cough threshold. Further investigations targeting different brain regions using multiple central intervention techniques to explore the underlying mechanisms are warranted.

Trial registration The study protocol was registered for the clinical trial in China (registration number: ChiCTR2100045618)

Confronting COVID-19-associated cough and the post-COVID syndrome: role of viral neurotropism, neuroinflammation, and neuroimmune responses

Cough is one of the most common presenting symptoms of COVID-19, along with fever and loss of taste and smell. Cough can persist for weeks or months after SARS-CoV-2 infection, often accompanied by chronic fatigue, cognitive impairment, dyspnoea, or pain-a collection of long-term effects referred to as the post-COVID syndrome or long COVID. We hypothesise that the pathways of neurotropism, neuroinflammation, and neuroimmunomodulation through the vagal sensory nerves, which are implicated in SARS-CoV-2 infection, lead to a cough hypersensitivity state. The post-COVID syndrome might also result from neuroinflammatory events in the brain. We highlight gaps in understanding of the mechanisms of acute and chronic COVID-19-associated cough and post-COVID syndrome, consider potential ways to reduce the effect of COVID-19 by controlling cough, and suggest future directions for research and clinical practice. Although neuromodulators such as gabapentin or opioids might be considered for acute and chronic COVID-19 cough, we discuss the possible mechanisms of COVID-19-associated cough and the promise of new anti-inflammatories or neuromodulators that might successfully target both the cough of COVID-19 and the post-COVID syndrome.

Evaluation of Naringenin as a Promising Treatment Option for COPD Based on Literature Review and Network Pharmacology

Chronic obstructive pulmonary disease (COPD) is a chronic respiratory disease characterized by incompletely reversible airflow limitation and seriously threatens the health of humans due to its high morbidity and mortality. Naringenin, as a natural flavanone, has shown various potential pharmacological activities against multiple pathological stages of COPD, but available studies are scattered and unsystematic. Thus, we combined literature review with network pharmacology analysis to evaluate the potential therapeutic effects of naringenin on COPD and predict its underlying mechanisms, expecting to provide a promising tactic for clinical treatment of COPD.

Peripheral and central mechanisms of cough hypersensitivity

Chronic cough is a difficult to treat symptom of many respiratory and some non-respiratory diseases, indicating that varied pathologies can underpin the development of chronic cough. However, clinically and experimentally it has been useful to collate these different pathological processes into the single unifying concept of cough hypersensitivity. Cough hypersensitivity syndrome is reflected by troublesome cough often precipitated by levels of stimuli that ordinarily don't cause cough in healthy people, and this appears to be a hallmark feature in many patients with chronic cough. Accordingly, a strong argument has emerged that changes in the excitability and/or normal regulation of the peripheral and central neural circuits responsible for cough are instrumental in establishing cough hypersensitivity and for causing excessive cough in disease. In this review, we explore the current peripheral and central neural mechanisms that are believed to be involved in altered cough sensitivity and present possible links to the mechanism of action of novel therapies that are currently undergoing clinical trials for chronic cough.

Perspectives on neuroinflammation contributing to chronic cough

Chronic cough can be a troublesome clinical problem. Current thinking is that increased activity and/or enhanced sensitivity of the peripheral and central neural pathways mediates chronic cough via processes similar to those associated with the development of chronic pain. While inflammation is widely thought to be involved in the development of chronic cough, the true mechanisms causing altered neural activity and sensitisation remain largely unknown. In this back-to-basics perspective article we explore evidence that inflammation in chronic cough may, at least in part, involve neuroinflammation orchestrated by glial cells of the nervous system. We summarise the extensive evidence for the role of both peripheral and central glial cells in chronic pain, and hypothesise that the commonalities between pain and cough pathogenesis and clinical presentation warrant investigations into the neuroinflammatory mechanisms that contribute to chronic cough. We open the debate that glial cells may represent an underappreciated therapeutic target for controlling troublesome cough in disease.