Effect of salbutamol on smoking related cough

Bronchodilator therapy for chronic cough

Experimental studies indicate that airway calibre increases the sensitivity of the afferents involved in the cough reflex but it has proved difficult to demonstrate that airway calibre increases the sensitivity of the afferents involved in the cough reflex. Therefore, bronchodilators might have a role, although rather minor, in the treatment of cough. However, although bronchodilators represent the standard of care in the treatment of airway obstruction associated with asthma or COPD, controversy persists regarding the mechanism(s) by which these agents alleviate cough. Furthermore, the available evidence indicates that the effects of bronchodilators on cough are rather inconsistent in humans and casts doubt on the appropriateness of the common practice of using bronchodilators in the treatment of patients with cough without any other evidence of airway obstruction. Regrettably, appropriate long-term trials specifically aimed at evaluating the clinical efficacy of bronchodilators in pathologic cough have not yet been performed. Therefore, properly executed clinical studies of bronchodilators in various types of acute and chronic pathologic cough are required.

Olodaterol attenuates citric acid-induced cough in naïve and ovalbumin-sensitized and challenged guinea pigs

Excessive coughing is a common feature of airway diseases. Different G-protein coupled receptors, including β2-adrenergic receptors (β2-AR), have been implicated in the molecular mechanisms underlying the cough reflex. However, the potential antitussive property of β2-AR agonists in patients with respiratory disease is a matter of ongoing debate. The aim of our study was to test the efficacy of the long-acting β2-AR agonist olodaterol with regard to its antitussive property in a pre-clinical model of citric acid-induced cough in guinea pigs and to compare the results to different clinically relevant β2-AR agonists. In our study β2-AR agonists were intratracheally administered, as dry powder, into the lungs of naïve or ovalbumin-sensitized guinea pigs 15 minutes prior to induction of cough by exposure to citric acid. Cough events were counted over 15 minutes during the citric acid exposure. Olodaterol dose-dependently inhibited the number of cough events in naïve and even more potently and with a greater maximal efficacy in ovalbumin-sensitized guinea pigs (p < 0.01). Formoterol and salmeterol showed a trend towards reducing cough. On the contrary, indacaterol demonstrated pro-tussive properties as it significantly increased the number of coughs, both in naïve and ovalbumin-sensitized animals (p < 0.001). In conclusion, olodaterol, at doses eliciting bronchodilation, showed antitussive properties in a model of citric acid-induced cough in naïve and ovalbumin-sensitized guinea pigs. This is in agreement with pre-clinical and clinical studies showing antitussive efficacy of β2-AR agonists. Indacaterol increased the number of coughs in this model, which concurs with clinical data where a transient cough has been observed after indacaterol inhalation. While the antitussive properties of β2-AR agonists can be explained by their ability to lead to the cAMP-induced hyperpolarization of the neuron membrane thereby inhibiting sensory nerve activation and the cough reflex, the mechanism underlying the pro-tussive property of indacaterol is not known.

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.

Comparison of the effectiveness of lidocaine and salbutamol on coughing provoked by intravenous remifentanil during anesthesia induction

BACKGROUND

Coughing is a side effect of opioids that is rarely studied. Here, we evaluated the incidence of remifentanil induced coughing during anesthesia induction in an attempt to identify its risk factors and to examine the preventive effects of lidocaine and salbutamol.

METHODS

A total of 237 patients scheduled to undergo general anesthesia were allocated randomly into three groups. Group C received no medication, while Group L received 2% lidocaine at 0.5 mg/kg intravenously 1 minute prior to remifentanil infusion and Group S inhaled one metered aerosol puff of salbutamol 15 minutes prior to entering the operating room. Remifentanil was infused at 5 ng/ml by target controlled infusion and coughing was measured for five minutes and graded as none, mild, moderate, or severe based on the number of coughs.

RESULTS

The incidences of coughing were 30.4%, 25.3%, and 35.4% in Groups C, L, and S, respectively. The incidences, onset times, and severity of coughing did not differ significantly among groups. In addition, multivariate analysis showed that non-smoking and a lower body weight were risk factors of remifentanil-induced coughing (odds ratio, 8.13; P = 0.024, 1.11, and 0.004, respectively).

CONCLUSIONS

The incidence of remifentanil-induced coughing was 30%. A total of 0.5 mg/kg lidocaine and 1 metered aerosol puff of salbutamol did not prevent coughing. Non-smoking and low body weight were found to be risk factors of remifentanil-induced coughing.

Beta-Adrenergic Agonists

Inhaled β₂-adrenoceptor (β₂-AR) agonists are considered essential bronchodilator drugs in the treatment of bronchial asthma, both as symptoms-relievers and, in combination with inhaled corticosteroids, as disease-controllers. In this article, we first review the basic mechanisms by which the β₂-adrenergic system contributes to the control of airway smooth muscle tone. Then, we go on describing the structural characteristics of β₂-AR and the molecular basis of G-protein-coupled receptor signaling and mechanisms of its desensitization/ dysfunction. In particular, phosphorylation mediated by protein kinase A and β-adrenergic receptor kinase are examined in detail. Finally, we discuss the pivotal role of inhaled β₂-AR agonists in the treatment of asthma and the concerns about their safety that have been recently raised.

Peripheral mechanisms II: the pharmacology of peripherally active antitussive drugs

Cough is an indispensable defensive reflex. Although generally beneficial, it is also a common symptom of diseases such as asthma, chronic obstructive pulmonary disease, upper respiratory tract infections, idiopathic pulmonary fibrosis and lung cancer. Cough remains a major unmet medical need and although the centrally acting opioids have remained the antitussive of choice for decades, they have many unwanted side effects. However, new research into the behaviour of airway sensory nerves has provided greater insight into the mechanisms of cough and new avenues for the discovery of novel non-opioid antitussive drugs. In this review, the pathophysiological mechanisms of cough and the development of novel antitussive drugs are reviewed.

Assessment of antitussive efficacy of dextromethorphan in smoking related cough: objective vs. subjective measures

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

Dextromethorphan is widely used as a cough suppressant in over the counter medications. Its efficacy in altering cough reflex sensitivity has been shown in healthy volunteers. In contrast evidence for an effect on clinically important cough is poor.

WHAT THIS STUDY ADDS

A significant decrease in evoked cough was seen with dextromethorphan compared with placebo. However, both placebo and active treatment improved subjective data to a similar degree. We doubt the validity of currently used objective tests in the investigation of antitussives.

AIMS

Using an established model of smokers cough we measured the antitussive effects of dextromethorphan compared with placebo.

METHODS

The study was a randomized, double-blind placebo controlled, crossover comparison of 22 mg 0.8 ml(-1) dextromethorphan delivered pregastrically with matched placebo. Objective and subjective measurements of cough were recorded. Subjective measures included a daily diary record of cough symptoms and the Leicester quality of life questionnaire. Cough frequency was recorded using a manual cough counter. The objective measure of cough reflex sensitivity was the citric acid, dose-response cough challenge.

RESULTS

Dextromethorphan was significantly associated with an increase in the concentration of citric acid eliciting an average of two coughs/inhalation (C2) when compared with placebo, 1 h post dose by 0.49 mM (95% CI 0.05, 0.45, geometric mean 3.09) compared with placebo 0.24 mM (geometric mean 1.74) P < 0.05 and at 2 h 0.57 mM (95% CI 0.01, 0.43, geometric mean 3.75) compared with placebo 0.34 mM (geometric mean 2.19) P < 0.05). There was a highly significant improvement in the subjective data when compared with baseline. However, there was no significant difference between placebo and active treatment. No correlation was seen between cough sensitivity to citric acid and recorded cough counts or symptoms. When both subjective and objective data were compared with screening data there was evidence of a marked 'placebo' effect.

CONCLUSIONS

The objective measure of cough sensitivity demonstrates dextromethorphan effectively diminishes the cough reflex sensitivity. However, subjective measures do not support this. Other studies support these findings, which may represent a profound sensitivity of the cough reflex to higher influences.

Changes in cough reflex sensitivity after cessation and resumption of cigarette smoking

Previous studies have shown that healthy cigarette smokers have diminished cough reflex sensitivity compared to healthy nonsmokers. We have recently demonstrated that cough reflex sensitivity is enhanced soon after smoking cessation, suggesting that diminished cough sensitivity in smokers results from chronic cigarette smoke-induced desensitization of airway cough receptors. In this study, we evaluated cough reflex sensitivity to capsaicin (C(5)) in 11 chronic smokers who had discontinued smoking for at least 2 weeks, and then resumed smoking. Two weeks after smoking cessation there was a significant enhancement of cough reflex sensitivity; mean (+/-SEM) log C(5) decreased from 1.77+/-0.18 to 1.47+/-0.14 (p=0.01). All subjects resumed smoking after 2-12 weeks of abstinence. Repeat capsaicin cough challenge was performed 14-23 days after resumption of smoking. Mean log C(5) increased compared to the last value obtained during the smoking cessation period: 1.42+/-0.15 vs. 1.77+/-0.16 (p=0.0004). Mean log C(5) after resumption of smoking returned to almost exactly the baseline value. Our findings suggest that the sensitivity of airway cough receptors is a dynamic phenomenon, promptly affected and modulated by changes in environmental conditions, such as the presence or absence of cigarette smoke.

The automatic recognition and counting of cough

Background

Cough recordings have been undertaken for many years but the analysis of cough frequency and the temporal relation to trigger factors have proven problematic. Because cough is episodic, data collection over many hours is required, along with real-time aural analysis which is equally time-consuming.

A method has been developed for the automatic recognition and counting of coughs in sound recordings.

Methods

The Hull Automatic Cough Counter (HACC) is a program developed for the analysis of digital audio recordings. HACC uses digital signal processing (DSP) to calculate characteristic spectral coefficients of sound events, which are then classified into cough and non-cough events by the use of a probabilistic neural network (PNN). Parameters such as the total number of coughs and cough frequency as a function of time can be calculated from the results of the audio processing.

Thirty three smoking subjects, 20 male and 13 female aged between 20 and 54 with a chronic troublesome cough were studied in the hour after rising using audio recordings.

Results

Using the graphical user interface (GUI), counting the number of coughs identified by HACC in an hour long recording, took an average of 1 minute 35 seconds, a 97.5% reduction in counting time. HACC achieved a sensitivity of 80% and a specificity of 96%. Reproducibility of repeated HACC analysis is 100%.

Conclusion

An automated system for the analysis of sound files containing coughs and other non-cough events has been developed, with a high robustness and good degree of accuracy towards the number of actual coughs in the audio recording.