Efficacy and tolerability of treatments for chronic cough: a systematic review and meta-analysis

Efficacy and tolerability of zinc acetate for treatment of chronic refractory cough: pilot randomised futility trial

Background

Cough is the most reported symptom in the United States, with chronic refractory cough representing significant morbidity to patients. Zinc acetate may have beneficial effects in the cough reflex pathway. We sought to assess the safety and efficacy of zinc acetate in the management of chronic refractory cough.

Study design and methods

This was a randomised, placebo-controlled, parallel-design pilot trial of individuals with chronic refractory cough. The effects of 6 weeks of zinc acetate versus placebo on quality of life and symptoms as measured by the Cough Quality-of-Life Questionnaire (CQLQ), Leicester Cough Questionnaire (LCQ), cough visual analogue score (C-VAS) and Global Assessment of Change in Cough (GACC) scores were evaluated. A futility analysis plan with a one-sided 80% confidence interval was used to compare treatment effect to published minimum clinically important differences (MCID) for each outcome.

Results

34 participants, 17 in each group, were enrolled and randomised. Participants were primarily white females with moderate-severe cough. Participants assigned to zinc acetate had a significant increase in serum zinc levels after 6 weeks, while those assigned to placebo did not. Both groups showed improvement in CQLQ, LCQ, C-VAS and GACC scores, but the treatment effects of zinc acetate versus placebo were small with confidence intervals that did not include the MCIDs.

Interpretation

We observed no benefit of zinc therapy over placebo on cough symptoms or quality of life and conclude that larger trials of zinc for chronic cough are not warranted.

Effectiveness and Safety of Codeine and Levodropropizine in Patients With Chronic Cough

BACKGROUND

Recent progress in chronic cough management includes controlling cough triggers and hypersensitivity using antitussives. Therefore, we investigated the effects and safety outcomes of antitussives, codeine and levodropropizine, in patients with chronic cough.

METHODS

We conducted an open-label, randomized comparative trial with newly referred patients with chronic cough. Patients were orally administered codeine (60 mg/day) and levodropropizine (180 mg/day) for 2 weeks. Cough severity, including the visual analog scale (VAS), Cough Symptom Score (CSS), Leicester Cough Questionnaire (LCQ), and safety for each treatment were assessed. The primary outcome was VAS score changes before and after 2 weeks of treatment.

RESULTS

Among the 88 participants, 45 and 43 in the codeine and levodropropizine groups, respectively, were included in the analysis. Changes in the VAS score were higher in the codeine group than in the levodropropizine group (35.11 ± 20.74 vs. 19.77 ± 24.83, P = 0.002). Patients administered codeine also had improved CSS (2.96 ± 2.35 vs. 1.26 ± 1.89, P < 0.001) and LCQ (3.28 ± 3.36 vs. 1.61 ± 3.53, P = 0.025) than those administered levodropropizine. Treatment-related adverse events, including drowsiness, constipation, and headaches, were more frequent in the codeine group than in the levodropropizine group. However, no significant differences existed in the adverse events leading to discontinuation.

CONCLUSION

Codeine is an effective and generally well-tolerated antitussive for chronic cough. However, it may induce side effects in some patients. Individual responses and adverse events should be carefully monitored when codeine is used to treat chronic cough.

A phase 3, randomized, double-blind, clinical study to evaluate the long-term safety and efficacy of gefapixant in Japanese adult participants with refractory or unexplained chronic cough

BACKGROUND

In two phase 3, global clinical trials (COUGH-1 and COUGH-2), the P2X3-receptor antagonist gefapixant significantly reduced objective 24-h cough frequency in participants with refractory or unexplained chronic cough (RCC or UCC) at a dosage of 45 mg twice daily (BID), with an acceptable safety profile. The primary objective of this phase 3, randomized, double-blind, parallel-group study was to assess the safety and tolerability of gefapixant in Japanese participants with RCC or UCC (ClinicalTrials.gov, NCT03696108; JAPIC-CTI, 184154).

METHODS

Participants aged ≥20 years with chronic cough lasting ≥4 months and a diagnosis of RCC or UCC despite treatment in accordance with Japanese Respiratory Society guidelines were randomized 1:1 to receive gefapixant 15 or 45 mg BID for 52 weeks. The primary objective was to evaluate the safety and tolerability of gefapixant, including adverse events (AEs) and discontinuations due to AEs. Cough-specific quality of life was assessed using the Leicester Cough Questionnaire as a secondary objective.

RESULTS

Of 169 randomized and treated participants, 63% were female and mean age was 58 years. Adverse events were reported by 79 (94%) and 82 (96%) participants in the 15- and 45-mg BID groups, respectively. Most treatment-related AEs were taste related. Discontinuations due to AEs occurred in 6 (7%) and 17 (20%) participants receiving gefapixant 15 or 45 mg BID, respectively. There were no serious treatment-related AEs or deaths. Leicester Cough Questionnaire total scores improved from baseline through Week 52.

CONCLUSIONS

Gefapixant had an acceptable safety profile, with no serious treatment-related AEs in Japanese participants.

Dextromethorphan Reduces Sign-Tracking but Not Goal-Tracking in Male Sprague-Dawley Rats

Sign-tracking is a well-known phenomenon in appetitive Pavlovian conditioning in which subjects approach the site of a conditioned stimulus (CS) associated with an appetitive unconditioned stimulus (US) even when the two are located separately. Control of sign-tracking may be important in rehabilitation from drug dependence to help ward off relapse. Recent studies have found success in using ketamine to reduce sign-tracking. In this study, we employed a similar but unscheduled drug, dextromethorphan (DXM), which affects many of the same molecular targets as ketamine, in an attempt to reduce sign-tracking in a standard paradigm. DXM was found to reduce sign-tracking at the doses examined in this study, while goal-tracking (approaching the site of the US rather than CS) was relatively unaffected. DXM offers advantages over ketamine in terms of use with patients and may have some utility in rehabilitation.

A Symptom-Directed Paradigm for the Evaluation and Management of Upper Respiratory Tract Infections

Upper respiratory tract infections are one of the most common challenges in ambulatory medicine. Effective evaluation involves identification, primarily through the history, of the dominant set of patient symptoms leading to accurate diagnosis. Certain more morbid illnesses that mimic common upper respiratory symptoms can also be excluded with this approach. Treatment should address patient preferences through an understanding of the limited utility of antibiotics and through tailored advisement of the numerous pharmacologic options for symptom relief.

Management of chronic refractory cough in adults

Cough is a common respiratory symptom that is considered to be chronic when it lasts more than eight weeks. When severe, chronic cough may significantly impact an individual's quality of life, and such patients are frequently referred for specialist evaluation. Current international guidelines provide algorithms for the management of chronic cough: in most cases, treatment of the underlying disease is sufficient to improve or resolve cough symptoms. Severe chronic cough may significantly affect patients' quality of life and necessitate frequent referral for specialist evaluations. In this narrative review, we summarize non-pharmacologic and pharmacologic management of adult patients with chronic cough of known cause that persists after proper treatment (chronic refractory cough, CRC) or chronic cough of unknown cause in adult patients. If chronic cough persists even after treatment of the underlying disease, or if the chronic cough is not attributable to any cause, then a symptomatic approach with neuromodulators may be considered, with gabapentin as the first choice, and opioids or macrolides as alternatives. Speech pathology treatment and/or neuromodulators should be discussed with patients and alternative options carefully considered, taking into account risk/benefit. Novel promising drugs are under investigation (e.g. P2×3 inhibitors), but additional studies are needed in this field. Speech pathology can be combined with a neuromodulator to give an enhanced treatment response of longer duration suggesting that non-pharmacologic treatment may play a key role in the management of CRC.

Mechanisms and Rationale for Targeted Therapies in Refractory and Unexplained Chronic Cough

Chronic cough, defined as a cough lasting > 8 weeks, is a common medical condition that exerts a substantial physical, mental, and social burden on patients. A subset of patients with chronic cough are troubled with a cough that persists despite optimal treatment of presumed associated common and uncommon conditions (refractory chronic cough; RCC) or in which no diagnosable cause for cough can be identified despite extensive assessment (unexplained chronic cough; UCC). Many of these patients exhibit clinical features of cough hypersensitivity, including laryngeal paresthesia, hypertussia, and allotussia. Over-the-counter cough remedies are ineffective and can lead to intolerable side effects when used for RCC/UCC, and the lack of approved treatments indicated for these conditions reflects a major unmet need. An increased understanding of the anatomy and neurophysiology of protective and pathologic cough has fostered a robust clinical development pipeline of several targeted therapies for RCC/UCC. This manuscript reviews the mechanisms presumed to underly RCC/UCC together with the rationale and clinical evidence for several targeted therapies currently under clinical investigation, including transient receptor potential channel antagonists, P2X3-receptor antagonists, voltage-gated sodium channel blockers, neuromodulators, and neurokinin-1-receptor antagonists. Finally, we provide an overview of targets that have been investigated in preclinical models of cough and other airway diseases that may hold future promise for clinical studies in RCC/UCC. Development of targeted therapies with different sites of action may foster a precision medicine approach to treat this heterogeneous, underserved patient population.

Association Between Prescribed Opioids and Infections in Patients With Neutropenia and Cancer

This nested case-control study examines the association of risk of infection with opioid use in immunocompromised patients.

Clinical Effects and Safety of Zhi Sou San for Cough: A Meta-Analysis of Randomized Trials

Introduction

Zhi Sou San (ZSS), a traditional Chinese prescription, has been widely applied in treating cough. The purpose of this meta-analysis was to evaluate the effectiveness and safety of ZSS for cough.

Methods

We searched relevant articles up to 5 March 2017 in seven electronic databases: the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, PubMed, Chinese National Knowledge Infrastructure (CNKI), Cqvip Database (VIP), China Biology Medicine disc (CBM), and Wanfang Data. Randomized controlled trials (RCTs) were eligible, regardless of blinding. The primary outcome was the total effective rate.

Results

Forty-six RCTs with a total of 4007 participants were identified. Compared with western medicine, ZSS significantly improved the total effective rate (OR: 4.45; 95% CI: 3.62–5.47) and the pulmonary function in terms of FEV1 (OR: 0.35; 95% CI: 0.24–0.46) and decreased the adverse reactions (OR: 0.05; 95% CI: 0.02–0.01) and the recurrence rate (OR: 0.30; 95% CI: 0.16–0.57). However, there was no significant improvement in the cough symptom score comparing ZSS with western medicine.

Conclusions

This meta-analysis shows that ZSS has significant additional benefits and relative safety in treating cough. However, more rigorously designed investigations and studies, with large sample sizes, are needed because of the methodological flaws and low quality of the included trials in this meta-analysis.

Analysis of the Literature on Chronic Cough in Children

Throughout childhood, various developmental phenomena influence the cough reflex. Among these are the modifications in the anatomy and functions of the respiratory tract and the central and peripheral nervous systems. Moreover, after birth, the immunological response undergoes progressive transformations with the acquisition of immune memory processes. These conditions make infections and airway abnormalities the overwhelming cause of chronic cough in children and infants. In children, chronic cough should be treated on the basis of etiology. The aim of this article is to provide thorough research and analysis of the medical literature published up to 2014 on chronic cough in children as a disease entity, including the epidemiologic, etiologic, diagnostic, prognostic, and therapeutic aspects. Our results demonstrate differences in the definition of chronic cough, the characteristics of diagnostic procedures, study settings, and prevalence of the main causes. However, few studies regarding epidemiology and the quality of life have been reported. Many therapeutic approaches that are considered effective in adults with chronic cough seem to be less efficient in children. Regardless of the setting, whether pediatric or non-pediatric, children with chronic cough should be carefully evaluated using child-specific protocols and algorithms. Awareness of the various pathophysiological conditions associated with chronic cough is vital for making a correct diagnosis and providing appropriate treatment. The prevalence of the different causes of chronic cough depends on various issues. Among these are the population under consideration and its age range, infectious disease control and prevention, the diagnostic procedures employed, disease definition criteria, and the local health system. Clinical guidelines for the management of children with chronic cough should take these components into consideration. Further clinical and basic research studies are still needed for better diagnosis, treatment, and prevention of chronic cough in children.

Cough, Cold, and Congestion

The common cold is a benign, self-limited, acute viral infection with associated symptoms of sneezing, rhinorrhea, nasal congestion, cough, and malaise. It is the most frequent acute illness in the industrialized world. Adults typically have two to three episodes of illness yearly while children can have up to five. The common cold is typically caused by viruses (including rhinovirus, RSV, coronavirus, and others), and often, no infecting organism is detected. Treatment is usually targeted at symptomatic relief. The differential diagnosis for cough, cold, and congestion is broad: ranging from non-emergent causes such as rhinitis to life-threatening illnesses such as pulmonary embolism. Careful assessment is necessary as misidentification can lead to inappropriate discharge of potentially lethal conditions.

Chronic cough: clinical characteristics and etiologies of 510 cases

BACKGROUND/AIM

To investigate the clinical features and underlying etiologies of chronic cough (CC).

MATERIALS AND METHODS

Five hundred and ten CC patients were enrolled. The phases, characteristics and associated clinical manifestations of CC among the gastroesophageal reflux cough (GERC), cough-variant asthma (CVA), and upper airway cough syndrome (UACS) groups were compared, and the diagnostic values of each group were evaluated by multiple regression analysis.

RESULTS

In the 510 patients, 404 had CC with single etiology-GERC (n = 175), CVA (n = 134), and UACS (n = 95). The characteristic features of GERC included gastric acid backflow symptoms such as sour-tasting regurgitation, heartburn, endoscopic esophagitis, poststimulation cough, frequent throat clearing, daytime mono-cough, and feelings of heaviness and pain in the chest. Patients with CVA typically exhibited sensitivity to smog and other irritants; the cough occurred mostly at night, and was associated with positive bronchodilator and provocation test results. The typical features of UACS included a history and/or symptoms of rhinitis, retropharyngeal postnasal drip, and wet cough occurring mostly during the daytime. The diagnostic specificities of above factors were >70%.

CONCLUSION

The most common causes of CC include GERC, CVA, and UACS, and their diagnosis is based on the characteristics of the underlying disease.

Evidence-based Evaluation and Management of Chronic Cough

Chronic cough is common and has a significant impact on the wellbeing of patients and the use and cost of health care services. Traditionally the approach to chronic cough in patients who are nonsmokers and are not taking an angiotensin-converting enzyme inhibitor has focused on the diagnosis and management of the upper airway cough syndrome, asthma, and reflux disease. The evaluation of patients with chronic cough frequently involves trials of empiric therapy for these 3 conditions. Chronic cough may be perpetuated by abnormalities of the cough reflex and sensitization of its afferent and central components.

Codeine versus placebo for chronic cough in children

BACKGROUND

Cough in children is a commonly experienced symptom that is associated with increased health service utilisation and burden to parents. The presence of chronic (equal to or more than four weeks) cough in children may indicate a serious underlying condition such as inhaled foreign body or bronchiectasis. Codeine (and derivative)-based medications are sometimes used to treat cough due to their antitussive properties. However, there are inherent risks associated with the use of these medications such as respiratory drive suppression, anaesthetic-induced anaphylaxis, and addiction. Metabolic response and dosage variability place children at increased risk of experiencing such side effects. A systematic review evaluating the quality of the available literature would be useful to inform management practices.

OBJECTIVES

To evaluate the safety and efficacy of codeine (and derivatives) in the treatment of chronic cough in children.

SEARCH METHODS

We searched the Cochrane Airways Group Register of Trials, Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (1946 to 8 June 2016), EMBASE (1974 to 8 June 2016), the online trials registries of the World Health Organization and ClinicalTrials.gov, and the bibliographic references of publications. We imposed no language restrictions.

SELECTION CRITERIA

We considered studies eligible for analysis when: the participant population included children aged less than 18 years with chronic cough (duration equal to or more than four weeks at the time of intervention); and the study design evaluated codeine or codeine-based derivatives against placebo through a randomised controlled trial.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the search results to determine eligibility against a standardised criteria, and we had a pre-planned method for analysis.

MAIN RESULTS

We identified a total of 556 records, of which 486 records were excluded on the basis of title and abstract. We retrieved the remaining 70 references in full to determine eligibility. No studies fulfilled the inclusion criteria of this review, and thus we found no evidence to support or oppose the use of codeine or derivatives as antitussive agents for chronic cough in children.While chronic cough is not the same as acute cough, systematic reviews on the use of codeine efficacy for acute cough in children conclude an overall lack of evidence to support or oppose the use of over-the-counter cough and cold medications containing codeine (or derivatives) for treatment of acute cough in children. The lack of sufficient evidence to support the use of these medications has been consistently reaffirmed by medical experts in international chronic cough guidelines and by governing medical and pharmaceutical authorities in the USA, Europe, Canada, New Zealand, and Australia. Due to the lack of sufficient evidence to support efficacy, and the known risks associated with use - in particular the increased risks for children - these medications are now not recommended for children less than 12 years of age and children between 12 to 18 years with respiratory conditions.

AUTHORS' CONCLUSIONS

This review has highlighted the absence of any randomised controlled trials evaluating codeine-based medications in the treatment of childhood chronic cough. Given the potential adverse events of respiratory suppression and opioid toxicity, national therapeutic regulatory authorities recommend the contraindication of access to codeine in children less than 12 years of age. We suggest that clinical practice adhere to clinical practice guidelines and thus refrain from using codeine or its derivatives to treat cough in children. Aetiological-based management practices continue to be advocated for children with chronic cough.

Efficacy and safety of Maekmoondong-tang for chronic dry cough: a study protocol for a randomized controlled trial

Background

Chronic cough, defined it lasts more than 8 weeks. The symptom is common, but highly troublesome, and it reduces quality of life. Despite much effort to develop a protocol for diagnosis and treatment of chronic cough, it remains problematic to determine its cause. As a result, treatment is often unsuccessful. Thus, there is much interest regarding the use of symptomatic drugs to control chronic cough.

Maekmoondong-tang is widely used in East Asian countries to treat chronic dry cough. Several experimental studies have reported that the herbal medicine has immunomodulatory and antitussive effects. Clinical studies involving Maekmoondong-tang have also been carried out; however, these studies have involved treating various diseases as a whole rather than chronic cough itself. Thus, we aim to evaluate the efficacy and safety of Maekmoondong-tang in chronic dry cough patients with a randomized controlled trial.

Methods/Design

This study is designed as an exploratory, single-center, placebo-controlled, double-blind, randomized, parallel group clinical trial. Patients with dry cough that has lasted more than 8 weeks will be recruited, after a 1-week run-in period, and randomly allocated to either the Maekmoondong-tang treatment group or the placebo group. The patients will receive Maekmoondong-tang or placebo granules 3 times daily for 4 weeks, with a 2-week follow-up. The primary outcome is a 10-point cough diary that will be recorded on a daily basis. The secondary outcomes comprise a cough visual analog scale, the Leicester Cough Questionnaire (Korean version), the Pattern Identification for Chronic Cough Questionnaire, biomarkers, safety testing, etc. Adverse events will also be reported.

Discussion

This trial will assess the efficacy and safety of Maekmoondong-tang in chronic dry cough.

Trial registration

Korean Clinical Trial Registry (http://cris.nih.go.kr; registration number: KCT0001646). Date of registration: October 5 2015

Treatment of Unexplained Chronic Cough: CHEST Guideline and Expert Panel Report

BACKGROUND

Unexplained chronic cough (UCC) causes significant impairments in quality of life. Effective assessment and treatment approaches are needed for UCC.

METHODS

This systematic review of randomized controlled trials (RCTs) asked: What is the efficacy of treatment compared with usual care for cough severity, cough frequency, and cough-related quality of life in patients with UCC? Studies of adults and adolescents aged > 12 years with a chronic cough of > 8 weeks' duration that was unexplained after systematic investigation and treatment were included and assessed for relevance and quality. Based on the systematic review, guideline suggestions were developed and voted on by using the American College of Chest Physicians organization methodology.

RESULTS

Eleven RCTs and five systematic reviews were included. The 11 RCTs reported data on 570 participants with chronic cough who received a variety of interventions. Study quality was high in 10 RCTs. The studies used an assortment of descriptors and assessments to identify UCC. Although gabapentin and morphine exhibited positive effects on cough-related quality of life, only gabapentin was supported as a treatment recommendation. Studies of inhaled corticosteroids (ICS) were affected by intervention fidelity bias; when this factor was addressed, ICS were found to be ineffective for UCC. Esomeprazole was ineffective for UCC without features of gastroesophageal acid reflux. Studies addressing nonacid gastroesophageal reflux disease were not identified. A multimodality speech pathology intervention improved cough severity.

CONCLUSIONS

The evidence supporting the diagnosis and management of UCC is limited. UCC requires further study to establish agreed terminology and the optimal methods of investigation using established criteria for intervention fidelity. Speech pathology-based cough suppression is suggested as a treatment option for UCC. This guideline presents suggestions for diagnosis and treatment based on the best available evidence and identifies gaps in our knowledge as well as areas for future research.

Cough hypersensitivity as a neuro-immune interaction

Cough is an intrinsic protective reflex. However, chronic cough affects a considerable proportion of general population and has a major impact on quality of life. A recent paradigm shift to ‘cough hypersensitivity syndrome’ suggests that chronic cough arises from hypersensitivity of the airway sensory nerves. As cough reflex is determined by interaction of the nervous system with immune system, persistent dysregulation of one or both of these systems may lead to chronic cough hypersensitivity. Here we review the current evidence for the neuro-immune interactions that underlie cough hypersensitivity and discuss future therapeutic strategies.

Symptom Prevalence, Symptom Severity, and Health-Related Quality of Life Among Young, Middle, and Older Adults With Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a chronic, life threatening illness that affects primarily women. The purpose of this study was to describe the prevalence of PAH symptoms and to determine whether there are differences in symptom severity and HRQOL in PAH symptoms among young, middle, and older adults with PAH. A cross sectional design was utilized. For all the age groups, shortness of breath (SOB) on exertion and fatigue were the two most prevalent symptoms. SOB on exertion had the highest symptom severity scores followed by fatigue for all groups. Symptom severity was significantly different among the groups for palpitations, abdominal swelling and nausea. For components of HRQOL, physical functioning worsened with age. All groups had diminished general health, role physical and vitality levels. There are some differences in symptom prevalence, symptom severity and HRQOL among young, middle and older adults. Awareness of these differences is important for healthcare providers to know and assess overtime. Palliative care should be an integral part of caring for patients with PAH.