Codeine and cough: an ineffective gold standard

Health Canada advisory impacts on the prevalence of oral codeine use in the Pediatric Canadian population: comparative study across provinces

Health Canada (HC) has, since 2013, issued safety alerts restricting the use of codeine-containing drugs among breastfeeding women and children/adolescents under 18 years of age. These products are linked to breathing problems among ultra-rapid CYP2D6 metabolizers and early use of opioid can lead to future opioid misuse. Using a multi-province population-based cohort study, we estimate the impact of federal safety alerts on annual rates of codeine use in the Canadian pediatric population. We analyzed data from 8,156,948 children/adolescents in five Canadian provinces between 1996 and 2021, using a common protocol. Children/adolescents were categorized as: ≤ 12 years (children) or > 12 years (adolescents). We defined codeine exposure by ≥ 1 prescription filled for codeine alone or combined with other medications. For both age categories, we obtained province-specific codeine prescription filling rates per calendar year by dividing the number of children/adolescents with ≥ 1 codeine prescription filled by the number of person-time. Annual rates of codeine use per 1000 persons vary by province from 3.0 (Quebec) to 10.1 (Manitoba) in children, and from 5.5 to 51.3 in adolescents. After the 2013 HC advisory, exposure decreased in all provinces (adjusted level change from - 0.6 to - 18.4%) in children and from - 2.1 to - 17.9% in adolescents after the 2016 advisory. Annual rates declined over time in all provinces, following HC safety alerts specific to each of the two age categories.

From bench to bedside: The role of cough hypersensitivity in chronic cough

BACKGROUND

Chronic cough is a burdensome condition characterized by persistent cough lasting longer than 8 weeks. Chronic cough can significantly affect quality of life, physical function and productivity, with many people troubled with a cough that lasts for months or even years. People with chronic cough commonly report a persistent urge to cough with frequent bouts of coughing triggered by innocuous stimuli, which has led to the concept of cough hypersensitivity.

MAIN BODY

Both central and peripheral neural pathways regulate cough, and although mechanisms driving development of cough hypersensitivity are not fully known, sensitization of these neural pathways contributes to excessive cough triggering in cough hypersensitivity. Effective therapies that control chronic cough are currently lacking. Recent therapeutic development has focused on several ion channels and receptors involved in peripheral activation of cough (e.g., transient receptor potential channels, P2 × 3 receptors and voltage-gated sodium channels) or central cough processing (e.g., neurokinin-1 [NK-1] receptors and nicotinic acetylcholine receptors).

CONCLUSION

These targeted therapies provide novel insights into mechanisms underlying cough hypersensitivity and may offer new treatment options for people with chronic cough. In this review, we explore preclinical and clinical studies that have improved our understanding of the mechanisms responsible for chronic cough and discuss the most promising targeted approaches to date, including trials of P2 × 3-receptor antagonists and NK-1-receptor antagonists.

Guidelines for the management of chronic cough in adults. Endorsed by the French speaking society of respiratory diseases (Société de Pneumologie de Langue Française, SPLF), the Société Française d'Oto-Rhino-Laryngologie et de Chirurgie de la Face et du Cou (SFORL), the Société Française de Phoniatrie et de Laryngologie (SFPL), the Société Nationale Française de Gastro-entérologie (SNFGE)

Patients with chronic cough experience a high alteration of quality of life. Moreover, chronic cough is a complex entity with numerous etiologies and treatments. In order to help clinicians involved in the management of patients with chronic cough, guidelines on chronic cough have been established by a group of French experts. These guidelines address the definitions of chronic cough and the initial management of patients with chronic cough. We present herein second-line tests that might be considered in patients with cough persistence despite initial management. Experts also propose a definition of unexplained or refractory chronic cough (URCC) in order to better identify patients whose cough persists despite optimal management. Finally, these guidelines address the pharmacological and non-pharmacological interventions useful in URCC. Thus, amitryptilline, pregabalin, gabapentin or morphine combined with speech and/or physical therapy are a mainstay of treatment strategies in URCC. Other treatment options, such as P2 × 3 antagonists, are being developed.

[Guidelines for the management of chronic cough in adults]

Patients with chronic cough experience major alteration in their quality of life. Given its numerous etiologies and treatments, this disease is a complex entity. To help clinicians involved in patient management of patients, guidelines have been issued by a group of French experts. They address definitions of chronic cough and initial management of patients with this pathology. We present herein the second-line tests that might be considered in patients whose coughing has persisted, notwithstanding initial management. The experts have also put forward a definition of unexplained or refractory chronic cough (URCC), the objective being to more precisely identify those patients whose cough persists despite optimal management. Lastly, these guidelines indicate the pharmacological and non-pharmacological interventions of use in URCC. Amitriptyline, pregabalin, gabapentin or morphine combined with speech and/or physical therapy are mainstays in treatment strategies. Other treatment options, such as P2X3 antagonists, are being developed and have generated high hopes among physicians and patients alike.

Brief History of Opioids in Perioperative and Periprocedural Medicine to Inform the Future

Background: Opioids and derivatives of opium had been used as analgesics for thousands of years before the introduction of inhalational anesthetic agents. Once these early volatile agents were in widespread use, opioids were used as part of anesthetic care for premedication, as intraoperative adjuncts to general anesthesia, and for the management of postoperative pain. Evidence of growing dependence on opioids in the perioperative and periprocedural patient is supported by the ongoing research to develop synthetic opioids and to customize the pharmacokinetics and pharmacodynamics to achieve specific therapeutic goals. Methods: We explore the history of opioid use in perioperative care as a means of future management in light of new persistent opioid abuse. Results: As the opium chemical structure has been modified, newer nonopioid analgesics have been approved and brought into clinical practice. Opioid-sparing and opioid-free anesthetic techniques are not only a possibility, but a reality. Conclusion: Continuing research in neurobiology and addiction genetics will ultimately lead to a pharmacogenetic approach to patients at risk for new persistent opioid abuse.

Cannabis sativa: Interdisciplinary Strategies and Avenues for Medical and Commercial Progression Outside of CBD and THC

Cannabis sativa (Cannabis) is one of the world’s most well-known, yet maligned plant species. However, significant recent research is starting to unveil the potential of Cannabis to produce secondary compounds that may offer a suite of medical benefits, elevating this unique plant species from its illicit narcotic status into a genuine biopharmaceutical. This review summarises the lengthy history of Cannabis and details the molecular pathways that underpin the production of key secondary metabolites that may confer medical efficacy. We also provide an up-to-date summary of the molecular targets and potential of the relatively unknown minor compounds offered by the Cannabis plant. Furthermore, we detail the recent advances in plant science, as well as synthetic biology, and the pharmacology surrounding Cannabis. Given the relative infancy of Cannabis research, we go on to highlight the parallels to previous research conducted in another medically relevant and versatile plant, Papaver somniferum (opium poppy), as an indicator of the possible future direction of Cannabis plant biology. Overall, this review highlights the future directions of cannabis research outside of the medical biology aspects of its well-characterised constituents and explores additional avenues for the potential improvement of the medical potential of the Cannabis plant.

Intra-Arterial, but Not Intrathecal, Baclofen and Codeine Attenuates Cough in the Cat

Centrally-acting antitussive drugs are thought to act solely in the brainstem. However, the role of the spinal cord in the mechanism of action of these drugs is unknown. The purpose of this study was to determine if antitussive drugs act in the spinal cord to reduce the magnitude of tracheobronchial (TB) cough-related expiratory activity. Experiments were conducted in anesthetized, spontaneously breathing cats (n = 22). Electromyograms (EMG) were recorded from the parasternal (PS) and transversus abdominis (TA) or rectus abdominis muscles. Mechanical stimulation of the trachea or larynx was used to elicit TB cough. Baclofen (10 and 100 μg/kg, GABA-B receptor agonist) or codeine (30 μg/kg, opioid receptor agonist) was administered into the intrathecal (i.t.) space and also into brainstem circulation via the vertebral artery. Cumulative doses of i.t. baclofen or codeine had no effect on PS, abdominal muscle EMGs or cough number during the TB cough. Subsequent intra-arterial (i.a.) administration of baclofen or codeine significantly reduced magnitude of abdominal and PS muscles during TB cough. Furthermore, TB cough number was significantly suppressed by i.a. baclofen. The influence of these drugs on other behaviors that activate abdominal motor pathways was also assessed. The abdominal EMG response to noxious pinch of the tail was suppressed by i.t. baclofen, suggesting that the doses of baclofen that were employed were sufficient to affect spinal pathways. However, the abdominal EMG response to expiratory threshold loading was unaffected by i.t. administration of either baclofen or codeine. These results indicate that neither baclofen nor codeine suppress cough via a spinal action and support the concept that the antitussive effect of these drugs is restricted to the brainstem.

Evaluation of a state law on opioid-prescribing behaviour and the void affecting codeine-containing antitussive syrup

BACKGROUND

Government opioid policies-such as the North Carolina Strengthen Opioid Misuse Prevention (STOP) Act-have aided in lowering the days' supply of opioid prescriptions. However, what effect do these laws have on codeine-containing antitussive syrup? We aimed to assess the effect of the North Carolina STOP Act on ED opioid prescriptions written for >5 days for acute pain/non-pain diagnoses and whether it had an effect on the prescribing of codeine-containing antitussive syrup.

METHODS

A retrospective study of two emergency departments, with an average annual census of 70 000 and 22 000 patients, from January to August of 2017 and 2018. We applied logistic regression techniques to calculate the odds of an opioid prescription for >5 days. Opioid medication categories were formed to determine relational proportions. Two-tailed z-tests were used to test the difference in proportions.

RESULTS

Our study included 5366 verifiable opioid prescriptions. The percentage of an opioid prescription for >5 days decreased by 3.3% (95% CI -1.8% to -4.7%, p<0.05) after the North Carolina STOP Act (9.8% to 6.5%; 95% CI 5.5% to 7.5%, p<0.05). There was no statistically significant change in the prescribing of codeine syrup for >5 days pre-STOP and post- STOP Act, respectively (91.5% and 90.4%; difference=-1.1%, p=0.83).

CONCLUSION

The North Carolina STOP Act was associated with a reduction in the overall percentage of opioid prescriptions for >5 days for acute pain/non-pain diagnoses. However, there was no statistically significant effect on the prescribing of codeine-containing antitussive syrup.

Treatment of Chronic Refractory Cough in Adults: Focus on Neuromodulators and Other Therapeutic Modalities

Objective: To evaluate the literature and educate health care professionals about the different management options for chronic refractory cough (CRC). Data Sources: Searches were performed through MEDLINE (1966 to July 2020) using OVID and EBSCOhost and EMBASE (1947 to July 2020) using OVID. Search terms included chronic cough, neurogenic cough, neuromodulators, chronic cough management, and chronic cough treatment. References of all relevant articles were further used to obtain additional articles. Study Selection and Data Extraction: This review includes articles in the English language and human trial literature. Twenty-three trials explored the use of oral neuromodulators in the management of CRC. Data Synthesis: CRC is a poorly understood disease that may have a complex neuropathic etiology. Oral neuromodulators, such as amitriptyline, baclofen, gabapentin, and pregabalin, continue to be the most commonly used agents for the management of CRC. Alternative pharmacological therapies such as botulinum toxin, anesthetic agents (benzonatate, lidocaine), and narcotic agents have efficacy data, and further research into effective doses and routes of administration is warranted. Alternative nonpharmacologic therapies more commonly used included speech pathology treatment. Conclusion: Several medication and alternative treatment interventions may be effective in managing CRC. Current studies used wide dosing and titration strategies, making it challenging to standardize therapy. No consistent method of assessing cough reflex was used between studies, as well as a lack of consistent randomization and small sample sizes. Additional research is needed to standardize treatment durations, optimum doses, and place in therapy of the available interventions in the management of CRC.

The Powerful Placebo Effect in Cough: Relevance to Treatment and Clinical Trials

Interest in the placebo effect of medicines has developed from the use of placebo treatments as controls in clinical trials into a whole new area of research around how placebos fit into a psychosocial model of therapeutics. The large placebo effect associated with cough medicines is both a problem and an opportunity for researchers: a problem for clinical trials on new actives as the active must beat the large placebo effect, and an opportunity for harnessing the placebo effect to produce effective cough medicines without any pharmacologically active ingredient. This review discusses the mechanisms associated with the placebo effect of cough medicines and distinguishes between a 'perceived placebo effect' and a true 'placebo effect'. The efficacy of sweeteners in cough syrups is discussed as well as viscosity, mucoadhesion, and flavoring. The complexity of modern cough medicines is demonstrated by an example of a medicine which contains one active ingredient, and eighteen excipients which provide a complex and intense sensory experience to enhance the placebo effect and complement the pharmacological activity of the medicine.

Aprepitant for Cough Suppression in Advanced Lung Cancer: A Randomized Trial

BACKGROUND

Although cough is a common and distressing symptom in patients with lung cancer, there is almost no evidence to guide treatment. Aprepitant, a centrally acting neurokinin-1 inhibitor, significantly decreased cough frequency in a pilot study.

METHODS

Patients with advanced lung cancer and cough lasting over 2 weeks despite a cough suppressant were randomized 1:1 to aprepitant 125 mg orally on day 1 and then 80 mg orally on days 2 to 7 with physician's choice of antitussive; or to physician's choice of antitussive alone. Evaluation was at baseline and on days 3, 7, 9, and 12. The primary end point was subjective cough improvement on day 9, measured by the Visual Analog Scale and Manchester Cough in Lung Cancer Scale. Secondary end points included quality of life (QoL) as measured by the European Organization for Research and Treatment of Cancer (EORTC) Core Quality of Life Questionnaire and the EORTC Lung Cancer-Specific Quality of Life Questionnaire and toxicity.

RESULTS

Between 2017 and 2018, 128 patients were randomized. Median baseline cough duration was 90 days. Mean Visual Analog Scale scores (in mm) at baseline and day 9 were 68 and 39 in the aprepitant arm and 62 and 49 in the control arm, respectively (P < .001); mean Manchester Cough in Lung Cancer Scale scores at baseline and day 9 were 33 and 23 in the aprepitant arm and 30 and 25 in the control arm, respectively (P < .001). Overall QoL was not significantly different between the two arms; however, aprepitant led to a significant improvement in the cough-specific QoL domain (P = .017). Aprepitant did not increase severe adverse events.

CONCLUSIONS

Aprepitant led to a significant improvement in cough in advanced lung cancer, without increasing severe side effects.

TRIAL REGISTRY

Clinical Trials Registry-India; No.: CTRI/2017/05/008691; URL: http://ctri.nic.in.

Feasibility, acceptability and potential effectiveness of an information technology-based, pharmacist-led intervention to prevent an increase in anticholinergic and sedative load among older community-dwelling individuals

Background:

Anticholinergic/sedative medications are frequently used by older people, despite their negative impacts on cognitive and physical function. We explore the feasibility, acceptability and potential effectiveness of an innovative information technology (IT)-based intervention to prevent an increase in anticholinergic/sedative load in older people.

Methods:

This was a prospective study in 51 Dutch community pharmacies. Pharmacists used an IT-based tool to identify patients aged ⩾65 years, with existing high anticholinergic/sedative loads (drug burden index ⩾2) and a newly initiated anticholinergic/sedative medication. We determined the following. Feasibility: number of eligible patients identified. Acceptability: pharmacists’ satisfaction with the intervention, pharmacists’ time investment and patients’ willingness to reduce medication use. Potential effectiveness: number of recommendations, rate of agreement of general practitioners (GPs) with proposed recommendations and factors associated with agreement. To evaluate the latter, pharmacists conducted medication reviews and proposed recommendations to GPs for 5–10 patients selected by the IT-based tool.

Results:

We included 305 patients from 47 pharmacies. Feasibility: a mean of 17.0 (standard deviation, 8.8) patients were identified per pharmacy. Acceptability: 43 pharmacists (91.5%) were satisfied with the intervention. The median time investment per patient was 33 min (range 6.5–210). Of 35 patients, 30 (85.7%) were willing to reduce medication use. Potential effectiveness: pharmacists proposed 351 recommendations for 212 patients (69.5%). GPs agreed with recommendations for 108 patients (35.4%). Agreement to stop a medication was reached in 19.8% of recommendations for newly initiated medications (37 of 187) and for 15.2% of recommendations for existing medications (25 of 164). Agreement was more likely for recommendations on codeine [odds ratio (OR) 3.30; 95% confidence interval (CI) 1.14–9.57] or medications initiated by a specialist (OR 2.85; 95% CI 1.19–6.84) and less likely for pharmacies with lower level of collaboration with GPs (OR 0.15; 95% CI 0.02–0.97).

Conclusion:

This innovative IT-based intervention was feasible, acceptable and potentially effective. In one-third of patients an increase in anticholinergic/sedative load was prevented within reasonable time investment.

Role of the dorsomedial medulla in suppression of cough by codeine in cats

The modulation of cough by microinjections of codeine in 3 medullary regions, the solitary tract nucleus rostral to the obex (rNTS), caudal to the obex (cNTS) and the lateral tegmental field (FTL) was studied. Experiments were performed on 27 anesthetized spontaneously breathing cats. Electromyograms (EMG) were recorded from the sternal diaphragm and expiratory muscles (transversus abdominis and/or obliquus externus; ABD). Repetitive coughing was elicited by mechanical stimulation of the intrathoracic airways. Bilateral microinjections of codeine (3.3 or 33mM, 54±16nl per injection) in the cNTS had no effect on cough, while those in the rNTS and in the FTL reduced coughing. Bilateral microinjections into the rNTS (3.3mM codeine, 34±1 nl per injection) reduced the number of cough responses by 24% (P<0.05), amplitudes of diaphragm EMG by 19% (P<0.01), of ABD EMG by 49% (P<0.001) and of expiratory esophageal pressure by 56% (P<0.001). Bilateral microinjections into the FTL (33mM codeine, 33±3 nl per injection) induced reductions in cough expiratory as well as inspiratory EMG amplitudes (ABD by 60% and diaphragm by 34%; P<0.01) and esophageal pressure amplitudes (expiratory by 55% and inspiratory by 26%; P<0.001 and 0.01, respectively). Microinjections of vehicle did not significantly alter coughing. Breathing was not affected by microinjections of codeine. These results suggest that: 1) codeine acts within the rNTS and the FTL to reduce cough in the cat, 2) the neuronal circuits in these target areas have unequal sensitivity to codeine and/or they have differential effects on spatiotemporal control of cough, 3) the cNTS has a limited role in the cough suppression induced by codeine in cats.

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.

Feed-forward and reciprocal inhibition for gain and phase timing control in a computational model of repetitive cough

We investigated the hypothesis, motivated in part by a coordinated computational cough network model, that second-order neurons in the nucleus tractus solitarius (NTS) act as a filter and shape afferent input to the respiratory network during the production of cough. In vivo experiments were conducted on anesthetized spontaneously breathing cats. Cough was elicited by mechanical stimulation of the intrathoracic airways. Electromyograms of the parasternal (inspiratory) and rectus abdominis (expiratory) muscles and esophageal pressure were recorded. In vivo data revealed that expiratory motor drive during bouts of repetitive coughs is variable: peak expulsive amplitude increases from the first cough, peaks about the eighth or ninth cough, and then decreases through the remainder of the bout. Model simulations indicated that feed-forward inhibition of a single second-order neuron population is not sufficient to account for this dynamic feature of a repetitive cough bout. When a single second-order population was split into two subpopulations (inspiratory and expiratory), the resultant model produced simulated expiratory motor bursts that were comparable to in vivo data. However, expiratory phase durations during these simulations of repetitive coughing had less variance than those in vivo. Simulations in which reciprocal inhibitory processes between inspiratory-decrementing and expiratory-augmenting-late neurons were introduced exhibited increased variance in the expiratory phase durations. These results support the prediction that serial and parallel processing of airway afferent signals in the NTS play a role in generation of the motor pattern for cough.

Antitussive, expectorant and analgesic effects of the ethanol seed extract of Picralima nitida (Stapf) Th. & H. Durand

Picralima nitida is used traditionally for management of cough. This study, therefore, investigated the antitussive, expectorant, and analgesic properties of the ethanolic seed extract of Picralima nitida (PNE), and ascertained its safety for use. Presence of secondary metabolites, and safety of PNE (10-2000 mg/kg) were evaluated by preliminary phytochemical screening, and by Irwin's test respectively. Percentage reduction in cough count, percentage increase in latency of cough, and percentage protection offered by PNE were established by the citric acid-induced cough, acetylcholine- and Histamine-induced bronchoconstriction models. Dunkin-Hartley guinea pigs were treated with 100-500 mg/kg PNE or reference drugs, dihydrocodiene, atropine, mepyramine. Expectorant property of PNE (100-1000 mg/kg) was determined using the tracheal phenol red secretion; with ammonium chloride as a reference medication. Percentage maximal possible analgesic effect in the tail immersion test and the total nociceptive score in acetic acid-induced abdominal writhes, after treatment of BALB/c mice with PNE (100-500 mg/kg), diclofenac, and morphine were also estimated. Phytochemical screening revealed the presence of tannins, alkaloids, glycosides, saponins, steroids, terpenoids and anthraquinones. PNEdid not cause any extract-related physical, pharmacological and CNS toxicities or mortality; sedation was observed at doses 1000-2000 mg/kg. It showed significant dose-dependent reduction in cough count, and increased cough latency. PNE (1000 mg/kg) enhanced tracheal phenol red secretion. PNE (100-500 mg/kg) significantly and dose dependently increased tail withdrawal latencies, and nociceptive score. PNE has antitussive, expectorant, and analgesic properties, with an LD50>2000 mg/kg.

Treatment of Acute Cough Due to the Common Cold: Multi-component, Multi-symptom Therapy is Preferable to Single-Component, Single-Symptom Therapy--A Pro/Con Debate

Acute viral upper respiratory tract infection, or, the common cold, affects essentially every human being, and cough is reported as its most frequent associated symptom. Billions of dollars are spent worldwide annually by individuals seeking relief from this multi-symptom syndrome. Thousands of non-prescription, over-the-counter products are available worldwide, aimed at relieving the various bothersome symptoms induced by the common cold. Differences of opinion exist as to whether optimal therapy for cough associated with the common cold consists of multi-component, multi-symptom cough/cold preparations, or, whether single-component medications, aimed at relief of specific symptoms, represent the optimal therapeutic approach. The 5th American Cough Conference, held in Washington, D.C. in June, 2015, provided an ideal forum for discussion and debate of this issue between two internationally recognized experts in the field of the common cold and its treatment.

Transporter-Mediated Disposition of Opioids: Implications for Clinical Drug Interactions

Opioid-related deaths, abuse, and drug interactions are growing epidemic problems that have medical, social, and economic implications. Drug transporters play a major role in the disposition of many drugs, including opioids; hence they can modulate their pharmacokinetics, pharmacodynamics and their associated drug-drug interactions (DDIs). Our understanding of the interaction of transporters with many therapeutic agents is improving; however, investigating such interactions with opioids is progressing relatively slowly despite the alarming number of opioids-mediated DDIs that may be related to transporters. This review presents a comprehensive report of the current literature relating to opioids and their drug transporter interactions. Additionally, it highlights the emergence of transporters that are yet to be fully identified but may play prominent roles in the disposition of opioids, the growing interest in transporter genomics for opioids, and the potential implications of opioid-drug transporter interactions for cancer treatments. A better understanding of drug transporters interactions with opioids will provide greater insight into potential clinical DDIs and could help improve opioids safety and efficacy.

Endogenous central suppressive mechanisms regulating cough as potential targets for novel antitussive therapies

Cough and the accompanying sensation known as the urge-to-cough are complex neurobiological phenomena dependent on sensory and motor neural processing at many levels of the neuraxis. In addition to the excitatory neural circuits that provide the positive drive for inducing cough and the urge-to-cough, recent studies have highlighted the existence of likely inhibitory central neural processes that can be engaged to suppress cough sensorimotor processing. In many respects, the balance between excitatory and inhibitory central cough control may be a critical determinant of cough in health and disease which argues for the importance of understanding the biology of these putative central inhibitory processes. This brief review summarises the current knowledge of the central circuits that govern voluntary and involuntary cough suppression and posits the notion of targeting central suppressive mechanisms as a treatment for disordered cough in disease.

A framework for understanding shared substrates of airway protection

Deficits of airway protection can have deleterious effects to health and quality of life. Effective airway protection requires a continuum of behaviors including swallowing and cough. Swallowing prevents material from entering the airway and coughing ejects endogenous material from the airway. There is significant overlap between the control mechanisms for swallowing and cough. In this review we will present the existing literature to support a novel framework for understanding shared substrates of airway protection. This framework was originally adapted from Eccles' model of cough²⁸ (2009) by Hegland, et al.⁴² (2012). It will serve to provide a basis from which to develop future studies and test specific hypotheses that advance our field and ultimately improve outcomes for people with airway protective deficits.

Recent additions in the treatment of cough

BACKGROUND

Worldwide, cough is regarded as a challenging clinical problem due to its frequency and often limited therapeutic options. Chronic cough that remains refractory to usual medical treatment causes significant quality of life impairment in people with this problem.

METHODS

We have examined current evidence on recent additions in the treatment of cough, specifically treatment of refractory chronic cough with speech pathology and gabapentin. Relevant randomised control trials, reviews and case reports were identified through a PubMed and SCOPUS search of English-language literature referring to these concepts over the last eight years.

SUMMARY

Of the one hundred and two articles comprising this review the majority investigated the role of the transient receptor potential (TRP) receptors TRP Vanilloid 1 (TRPV1) and TRPA1 in cough and the potential of TRP antagonists as effective anti-tussives. However, these have only been tested in the laboratory and therefore their clinical effectiveness is unknown. Behavioural treatments such as speech pathology have gained momentum and this was evident in the increasing number of articles investigating its positive effect on cough. Investigation on the effectiveness of neuromodulating medications in the treatment of cough have been supported primarily through case series reports and prospective reviews however; their use (particularly gabapentin) has been significantly advanced through recently conducted randomised controlled trials.

CONCLUSIONS

Recent additions in the treatment of chronic cough have been significant as they consider cough to have a unifying diagnosis of cough hypersensitivity with or without the presence of a neuropathic basis. Primarily, effective treatments for chronic cough target these areas and include behavioural treatment such as speech pathology and pharmaceutical treatment with neuromodulating medications such as gabapentin.

Evidence-based diagnosis and management of acute bronchitis

Acute bronchitis is a common respiratory infection seen in primary care settings. This article examines the current evidence for diagnosis and management of acute bronchitis in adults and provides recommendations for primary care clinical practice.

Variability of the pharyngeal phase of swallow in the cat

Objective

The pharyngeal phase of swallow has been thought to be a stereotypical motor behavior.

Study Design

This is a prospective, preclinical, hypothesis driven, one group by three-task design.

Methods

We sought to compare the effects of pharyngeal swabbing, water only, and water plus punctate mechanical stimulation on the spatiotemporal features of the pharyngeal phase of swallow in the cat. Swallow was elicited under these three conditions in six anaesthetized cats. Electromyographic activity was recorded from seven muscles used to evaluate swallow: mylohyoid, geniohyoid, thyrohyoid, thyroarytenoid, thyropharyngeus, cricopharyngeus, and parasternal.

Results

Pharyngeal swabbing in comparison to the other stimulus conditions, results in decreases in post-swallow cricopharyngeus activity (upper esophageal sphincter); a significant increase in parasternal (schluckatmung; swallow breath) activity; and increases in thyrohyoid (laryngeal elevator), thyroarytenoid (laryngeal adductor) and parasternal muscles burst duration. Pearson correlations were found of moderate strength between 19% of burst duration comparisons and weak to moderate relationships between 29% of burst amplitude comparisons. However, there were no positive significant relationships between phase durations and electromyogram amplitudes between any of the muscles studied during swallow.

Conclusions

The results support the concept that a stereotypical behavior, such as pharyngeal swallowing in animal models, can be modified by sensory feedback from pharyngeal mucosal mechanoreceptors. Furthermore, differences in swallow phase durations and amplitudes provide evidence that separate regulatory mechanisms exist which regulate spatial and temporal aspects of the behavior.

Antitussive drugs--past, present, and future

Cough remains a serious unmet clinical problem, both as a symptom of a range of other conditions such as asthma, chronic obstructive pulmonary disease, gastroesophageal reflux, and as a problem in its own right in patients with chronic cough of unknown origin. This article reviews our current understanding of the pathogenesis of cough and the hypertussive state characterizing a number of diseases as well as reviewing the evidence for the different classes of antitussive drug currently in clinical use. For completeness, the review also discusses a number of major drug classes often clinically used to treat cough but that are not generally classified as antitussive drugs. We also reviewed a number of drug classes in various stages of development as antitussive drugs. Perhaps surprising for drugs used to treat such a common symptom, there is a paucity of well-controlled clinical studies documenting evidence for the use of many of the drug classes in use today, particularly those available over the counter. Nonetheless, there has been a considerable increase in our understanding of the cough reflex over the last decade that has led to a number of promising new targets for antitussive drugs being identified and thus giving some hope of new drugs being available in the not too distant future for the treatment of this often debilitating symptom.

A One-Step Synthesis of β-Bromocodide from Codeine

Opioid analgesics are the treatment of choice for chronic, severe pain. During the course of developing new derivatives of morphine and codeine, we observed an unanticipated S_N2' substitution reaction product during an attempted 3-O-demethylation of codeine using BBr₃. NMR spectroscopy and X-ray crystallographic data indicate that a significant product is β-bromocodide, a useful intermediate for the production of C-6-demethoxythebaine derivatives. Herein we report the first, single-step synthesis of β-bromocodide.

Coordination of cough and swallow: a meta-behavioral response to aspiration

Airway protections is the prevention and/or removal of material by behaviors such as cough and swallow. We hypothesized these behaviors are coordinated to respond to aspiration. Anesthetized animals were challenged with simulated aspiration that induced both coughing and swallowing. Electromyograms of upper airway and respiratory muscles together with esophageal pressure were recorded to identify and evaluate cough and swallow. During simulated aspiration, both cough and swallow intensity increased and swallow duration decreased consistent with rapid pharyngeal clearance. Phase restriction between cough and swallow was observed; swallow was restricted to the E2 phase of cough. These results support three main conclusions: 1) the cough and swallow pattern generators are tightly coordinated so as to generate a protective meta-behavior; 2) the trachea provides feedback on swallow quality, informing the brainstem about aspiration incidences; and 3) the larynx and upper esophageal sphincter act as two separate valves controlling the direction of positive and negative pressures from the upper airway into the thorax.

Coordination of cough and swallow: a meta-behavioral response to aspiration

Airway protections is the prevention and/or removal of material by behaviors such as cough and swallow. We hypothesized these behaviors are coordinated to respond to aspiration. Anesthetized animals were challenged with simulated aspiration that induced both coughing and swallowing. Electromyograms of upper airway and respiratory muscles together with esophageal pressure were recorded to identify and evaluate cough and swallow. During simulated aspiration, both cough and swallow intensity increased and swallow duration decreased consistent with rapid pharyngeal clearance. Phase restriction between cough and swallow was observed; swallow was restricted to the E2 phase of cough. These results support three main conclusions: 1) the cough and swallow pattern generators are tightly coordinated so as to generate a protective meta-behavior; 2) the trachea provides feedback on swallow quality, informing the brainstem about aspiration incidences; and 3) the larynx and upper esophageal sphincter act as two separate valves controlling the direction of positive and negative pressures from the upper airway into the thorax.

Central neural circuits for coordination of swallowing, breathing, and coughing: predictions from computational modeling and simulation

The purpose of this article is to update the otolaryngologic community on recent developments in the basic understanding of how cough, swallow, and breathing are controlled. These behaviors are coordinated to occur at specific times relative to one another to minimize the risk of aspiration. The control system that generates and coordinates these behaviors is complex, and advanced computational modeling methods are useful tools to elucidate its function.

Shortness of breath and cough in patients in palliative care

BACKGROUND

Shortness of breath and cough are common, disturbing symptoms in patients receiving palliative care. They arise in 10% to 70% of patients with advanced cancer and in 60% to nearly 100% of patients with non-malignant underlying diseases, depending on the type of disease.

METHODS

This review is based on a selective literature search in the Medline, Embase, and PsycInfo databases and on current recommendations from Germany and other countries, as well as on the authors' personal experience.

RESULTS

Some general measures to address these problems are reassurance, development of an emergency plan, physical activity, and relaxation exercises. Supportive non-pharmacological measures may include the use of a rollator (level of evidence [LoE] 1-), a cool draft of air as from a handheld fan (LoE 1-), physiotherapy, and respiratory therapy. There is good evidence (LoE 1+) to support the administration of opioids as the medications of choice; benzodiazepines are often used, but a meta-analysis did not reveal any statistically significant benefit (LoE 1+). Expectorants can help patients who cough with marked sputum formation. Antitussants suppress the cough reflex both peripherally and centrally (LoE 1+ to 3). Opioids, including morphine (LoE 1-) and dextromethorphan (LoE 1-), are effective antitussants with low toxicity.

CONCLUSION

In most patients, shortness of breath and cough can be relieved by a series of therapeutic measures.

Influence of baclofen on laryngeal and spinal motor drive during cough in the anesthetized cat

OBJECTIVES/HYPOTHESIS

The antitussive properties of (±) baclofen on laryngeal muscle activities have not been determined. The hypothesis of this study was that administration of (±) baclofen would suppress upper airway muscle motor activity in a dose-dependent manner during cough.

STUDY DESIGN

This is a prospective, preclinical, hypothesis-driven, paired design.

METHODS

Electromyograms of the parasternal, rectus abdominis, thyroarytenoid, posterior cricoarytenoid, and thyrohyoid were measured, along with esophageal pressure. Cough was elicited by mechanical stimulation of the lumen of the intrathoracic trachea in spontaneously breathing cats.

RESULTS

Baclofen (±) (3-10 μg kg(-1) i.a.) induced decreases in the electromyogram amplitude of the rectus abdominis motor drive during coughing, the inspiratory and active expiratory (E1) phases of cough, and cough number per epoch. There was no effect of (±) baclofen on the EMG amplitudes of any of the laryngeal muscles, the parasternal, or the duration of the passive expiratory (E2) phase.

CONCLUSIONS

Results from the present study indicate differential control mechanisms for laryngeal and inspiratory motor drive during cough, providing evidence of a control system regulating laryngeal activity and inspiratory spinal drive that is divergent from the control of expiratory spinal motoneurons.

Co-ordination of cough and swallow in vivo and in silico

Coughing and swallowing are airway-protective behaviours. The pharyngeal phase of swallowing prevents aspiration of oral material (saliva, food and liquid) by epiglottal movement, laryngeal adduction and clearing of the mouth and pharynx. Coughing is an aspiration-response behaviour that removes material from the airway. Co-ordination of these behaviours is vital to protect the airway from further aspiration-promoting events, such as a swallowing during the inspiratory phase of coughing. The operational characteristics, primary strategies and peripheral inputs that co-ordinate coughing and swallowing are unknown. This lack of knowledge impedes understanding and treatment of deficits in airway protection, such as the co-occurrence of dystussia and dysphagia common in Parkinson's and Alzheimer's diseases, as well as stroke.

Where are the new cough treatments: a debriefing of recent clinical proof-of-concept trials with the NOP agonist SCH 486757

Cough continues to be one of the top reasons why patients seek medical attention from health care providers. The prescription antitussive market is dominated by opioids, such as codeine that produces inconsistent efficacy and is often accompanied by significant side effect liabilities. Consequently, cough represents an unmet medical need and an underserved market. Yet, against the backdrop of increasing cough research, the development of novel treatments has been exceptionally challenging with dextromethorphan being the last US drug approved for cough almost a half century ago. We support the position that an unambiguous and actionable 'road map' that clearly delineates the pathway forward for new cough suppressants from basic research to and beyond clinical proof-of-concept studies will be an important aspect for future success of this pharmacological class of drug. Pivotal to the establishment of such a road map will be the review of lessons learned from antitussive agents that have been recently progressed to proof-of-concept trials. In the present commentary, we briefly discuss observations and challenges pertaining to SCH 486757, a selective orally active NOP agonist that has recently advanced to human antitussive testing.

Uptake of codeine into intestinal epithelial (Caco-2) and brain endothelial (RBE4) cells

Orally administered codeine has to permeate both the intestinal and the blood-brain barrier in order to act as analgesic and cough suppressant. In this study we characterized the uptake of codeine at intestinal epithelial (Caco-2) and brain endothelial (RBE4) cells. At both cell types, uptake of [(3)H]codeine was independent of an inwardly directed Na(+) gradient. Uptake was, however, strongly stimulated by an outwardly directed H(+) gradient and inhibited by the protonophore FCCP. [(3)H]Codeine uptake into Caco-2 cells was strongly temperature dependent. In the presence of excess amounts of unlabeled codeine, the uptake was inhibited by up to 87% (Caco-2) or 94% (RBE4), respectively. Synthetic opioids and some non-opioid organic cations like propranolol, pyrilamine and quinidine potently inhibited [(3)H]codeine uptake. Several prototype substrates of known transporters for amino acids, neurotransmitters and organic cations were ineffective. Our data are consistent with a hypothetic saturable, H(+)-dependent (antiport) mechanism not yet identified on a molecular level. The pH dependence of codeine uptake and its intracellular accumulation can partially also be explained by a model comprising diffusional membrane permeation of unionized species of codeine followed by codeine sequestration into acidic vesicles and distribution into cellular lipids.

Pharmacological profile of the NOP agonist and cough suppressing agent SCH 486757 (8-[Bis(2-Chlorophenyl)Methyl]-3-(2-Pyrimidinyl)-8-Azabicyclo[3.2.1]Octan-3-Ol) in preclinical models

We describe the pharmacological and pharmacokinetic profiles of SCH 486757, a nociceptin/orphanin FQ peptide (NOP) receptor agonist that has recently entered human clinical trials for cough. SCH 486757 selectively binds human NOP receptor (K(i)=4.6+/-0.61nM) over classical opioid receptors. In a guinea pig capsaicin cough model, SCH 486757 (0.01-1mg/kg) suppressed cough at 2, 4, and 6h post oral administration with a maximum efficacy occurring at 4h equivalent to codeine, hydrocodone, dextromethorphan and baclofen. The antitussive effects of SCH 486757 (3.0mg/kg, p.o.) was blocked by the NOP receptor antagonist J113397 (12mg/kg, i.p.) but not by naltrexone (10mg/kg, p.o.). SCH 486757 does not produce tolerance to its antitussive activity after a 5-day BID dosing regimen. After acute and chronic dosing paradigms, SCH 486757 (1mg/kg) inhibited capsaicin-evoked coughing by 46+/-9% and 40+/-11%, respectively. In a feline mechanically-evoked cough model, SCH 486757 produces a maximum inhibition of cough and expiratory abdominal electromyogram amplitude of 59 and 61%, respectively. SCH 486757 did not significantly affect inspiratory electromyogram amplitude. We examined the abuse potential of SCH 486757 (10mg/kg, p.o.) in a rat conditioned place preference procedure which is sensitive to classical drugs of abuse, such as amphetamine and morphine. SCH 486757 was without effect in this model. Finally, SCH 486757 displays a good oral pharmacokinetic profile in the guinea pig, rat and dog. We conclude that SCH 486757 has a favorable antitussive profile in preclinical animal models.

Importance of placebo effect in cough clinical trials

Cough is a unique symptom because, unlike sneeze and other symptoms, it can be under voluntary control and this complicates clinical trials on cough medicines. All over-the-counter cough medicines (OTC) are very effective treatments because of their placebo effect. The placebo effect is enhanced by expectancy related to advertising, brand, packaging, and formulation. This placebo effect creates a problem for the conduct of clinical trials on OTC cough medicines that attempt to demonstrate the efficacy of a pharmacological agent above that of any placebo effect. Up to 85% of the efficacy of some cough medicines can be attributed to a placebo effect. The placebo effect apparent in clinical trials consists of several components: natural recovery, regression of cough response toward mean, demulcent effect, effect of sweetness, voluntary control, and effects related to expectancy and meaning of the treatment. The placebo effect has been studied most in the pain model, and placebo analgesia is reported to depend on the activation of endogenous opioid systems in the brain; this model may be applicable to cough. A balanced placebo design may help to control for the placebo effect, but this trial design may not be acceptable due to deception of patients. The placebo effect in clinical trials may be controlled by use of a crossover design, where feasible, and the changes in the magnitude of the placebo effect in this study design are discussed.

Utilizing nature as a source of new probes for opioid pharmacology

Background: Traditional and current opioid pharmacology is fundamentally based on interactions between opioid receptors and compounds isolated from natural sources. Adverse effects associated with opioids have led to the search for compounds with diminished side effects. Discussion: Recent discoveries of non-nitrogenous and structurally diverse alkaloids as novel opioid ligands have led to renewed interest in the development of novel chemotypes for opioid receptors. Conclusion: The strong history of natural products as opioid receptor ligands suggests that nature is one of the most promising for the identification of novel opioids. This review highlights the vast potential of investigating natural products as novel probes of opioid receptors.

Central mechanisms IV: conscious control of cough and the placebo effect

Early animal experiments on cough developed the concept that cough was an involuntary reflex controlled from areas in the brainstem and that cough could be inhibited by centrally acting medicines such as codeine. Studies on the voluntary control of cough, the urge to cough and the placebo effect of cough medicines have demonstrated that human cough is more complex than a brainstem reflex. The efficacy and mechanism of action of centrally acting cough medicines such as codeine and dextromethorphan is now in dispute, and codeine is no longer accepted as a gold-standard antitussive. This review puts forward a cough model that includes three types of cough: (1) reflex cough, caused by the presence of food or fluid in the airway--this type of cough is not under conscious control and can occur in the unconscious subject during general anaesthesia; (2) voluntary cough--under conscious control that is abolished with general anaesthesia; (3) cough in response to sensation of airway irritation--this type of cough causes an urge to cough that initiates voluntary cough and may only be present in the conscious subject. The review proposes that human cough associated with respiratory disease is under conscious control and is mainly related to a sensation of airway irritation and an urge to cough (type 3). The review discusses the summation of sensory input from the airway in a brainstem integrator that reaches a threshold to cause reflex cough. Subthreshold conditions in the cough integrator may be perceived as an urge to cough that is under voluntary control. The cough model presented in the review has implications for the development of cough medicines as it indicates that the older view of cough medicines acting in the brainstem area to inhibit the cough reflex may need to be revised to include conscious control of cough as an important mechanism of cough in man.

TRPV1 antagonists as potential antitussive agents

Cough is an important defensive pulmonary reflex that removes irritants, fluids, or foreign materials from the airways. However, when cough is exceptionally intense or when it is chronic and/or nonproductive it may require pharmacologic suppression. For many patients, antitussive therapies consist of OTC products with inconsequential efficacies. On the other hand, the prescription antitussive market is dominated by older opioid drugs such as codeine. Unfortunately, "codeine-like" drugs suppress cough at equivalent doses that also often produce significant ancillary liabilities such as GI constipation, sedation, and respiratory depression. Thus, the discovery of a novel and effective antitussive drug with an improved side effect profile relative to codeine would fulfill an unmet clinical need in the treatment of cough. Afferent pulmonary nerves are endowed with a multitude of potential receptor targets, including TRPV1, that could act to attenuate cough. The evidence linking TRPV1 to cough is convincing. TRPV1 receptors are found on sensory respiratory nerves that are important in the generation of the cough reflex. Isolated pulmonary vagal afferent nerves are responsive to TRPV1 stimulation. In vivo, TRPV1 agonists such as capsaicin elicit cough when aerosolized and delivered to the lungs. Pertinent to the debate on the potential use of TRPV1 antagonist as antitussive agents are the observations that airway afferent nerves become hypersensitive in diseased and inflamed lungs. For example, the sensitivity of capsaicin-induced cough responses following upper respiratory tract infection and in airway inflammatory diseases such as asthma and COPD is increased relative to that of control responses. Indeed, we have demonstrated that TRPV1 antagonism can attenuate antigen-induced cough in the allergic guinea pig. However, it remains to be determined if the emerging pharmacologic profile of TRPV1 antagonists will translate into a novel human antitussive drug. Current efforts in clinical validation of TRPV1 antagonists revolve around various pain indications; therefore, clinical evaluation of TRPV1 antagonists as antitussive agents will have to await those outcomes.