Influence of chinoin-170, a novel antitussive, on the mucociliary activity in respiratory airways of rats, rabbits, guinea-pigs and man

Theobromine for the treatment of persistent cough: a randomised, multicentre, double-blind, placebo-controlled clinical trial

BACKGROUND

To investigate the effect of BC1036 on health-related quality of life (QOL) in subjects with persistent cough. The secondary objective was to investigate the effect of BC1036 on subjective cough severity.

METHODS

This was a randomised, multicentre, double-blind, placebo-controlled, parallel-group study in 289 subjects with persistent cough. Subjects received BC1036 or placebo twice daily for 14 days. The primary endpoint comprised cough-related QOL assessed using the validated Leicester Cough Questionnaire (LCQ) at Day 14. Secondary endpoints comprised the LCQ scores at Day 7 and Day 28, cough severity VAS scores at each visit and pulmonary function tests.

RESULTS

At baseline, mean total LCQ score in the BC1036 group was lower (i.e., worse QOL) than placebo (P<0.001), indicating significant between-group heterogeneity. Mean baseline-adjusted change in LCQ score at Day 14 was greater for BC1036 [mean (SD) 2.4±3.5] compared to placebo [mean (SD) score 2.2±3.0], but did not reach statistical significance (P=0.60). Mean cough severity VAS score decreased to a greater extent in the BC1036 group compared to placebo, but again the results were not statistically significant (-12.2±23.28 in BC1036 group and -11.0±21.34 in placebo group at Day 14, P=0.688). There was no significant change in pulmonary function measurements. The adverse event (AE) profile was similar in both groups.

CONCLUSIONS

This study showed that BC1036 was well tolerated and, although the primary endpoint did not achieve statistical significance, the magnitude of improvement was greater with BC1036 compared to placebo with respect to improving QOL and reducing cough severity.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov: NCT01656668.

Theophylline inhibits the cough reflex through a novel mechanism of action

Background

Theophylline has been used in the treatment of asthma and chronic obstructive pulmonary disease for more than 80 years. In addition to bronchodilator and anti-inflammatory activity, clinical studies have suggested that theophylline acts as an antitussive agent. Cough is the most frequent reason for consultation with a family doctor, and treatment options are limited. Determining how theophylline inhibits cough might lead to the development of optimized compounds.

Objective

We sought to investigate the inhibitory activity of theophylline on vagal sensory nerve activity and the cough reflex.

Methods

Using a range of techniques, we investigated the effect of theophylline on human and guinea pig vagal sensory nerve activity in vitro and on the cough reflex in guinea pig challenge models.

Results

Theophylline was antitussive in a guinea pig model, inhibited activation of single C-fiber afferents in vivo and depolarization of human and guinea pig vagus in vitro, and inhibited calcium influx in airway-specific neurons in vitro. A sequence of pharmacological studies on the isolated vagus and patch clamp and single-channel inside-out experiments showed that the effect of theophylline was due to an increase in the open probability of calcium-activated potassium channels. Finally, we demonstrated the antitussive activity of theophylline in a cigarette smoke exposure model that exhibited enhanced tussive responses to capsaicin.

Conclusion

Theophylline inhibits capsaicin-induced cough under both normal and “disease” conditions by decreasing the excitability of sensory nerves through activation of small- and intermediate-conductance calcium-activated potassium channels. These findings could lead to the development of optimized antitussive compounds with a reduced side effect potential.

Clinical cough V: complementary and alternative medicine: therapy of cough

We review the actions of complementary and alternative medicines (CAMs) in the treatment of cough and of the conditions associated with it; in particular asthma and upper respiratory tract infections. These therapies may work (1) peripherally, at the sites in the airways and lungs at which cough is being activated, (2) in the brainstem, where the neural "cough center" is situated, or (3) at the cerebral cortex, where cough can be initiated, suppressed or modified by conscious or unconscious controls. Of the large number of trials of CAMs against cough, most are inadequate in design. It may be difficult to randomize selection. Blinding is often impossible both for the patient and the therapist, and adequate placebo controls may be difficult to devise. The patient can usually identify the "active" treatment by the taste or smell of a medicine, or from the approach and apparatus being used. Pure chemicals can be extracted from many of the herbs used as antitussives, and can be shown to be effective in randomized, blind, and controlled trials, but it does not follow that the herb itself, used in the recommended formula and shown to be antitussive, acts by this agency unless a placebo effect is ruled out. A few herbs are identified where the evidence points to a true antitussive action. Of nonherbal treatments, the few positive results are usually outweighed by the larger number of negative ones. Thus, in general, CAMs for cough are welcomed enthusiastically by the patient but lack sound evidence for their efficacy. Antitussive chemicals can be extracted from many herbs, but it is no more than a reasonable hypothesis that the herb itself acts through this pathway.

Theobromine inhibits sensory nerve activation and cough

Cough is a common and protective reflex, but persistent coughing is debilitating and impairs quality of life. Antitussive treatment using opioids is limited by unacceptable side effects, and there is a great need for more effective remedies. The present study demonstrates that theobromine, a methylxanthine derivative present in cocoa, effectively inhibits citric acid-induced cough in guinea-pigs in vivo. Furthermore, in a randomized, double-blind, placebo-controlled study in man, theobromine suppresses capsaicin-induced cough with no adverse effects. We also demonstrate that theobromine directly inhibits capsaicin-induced sensory nerve depolarization of guinea-pig and human vagus nerve suggestive of an inhibitory effect on afferent nerve activation. These data indicate the actions of theobromine appear to be peripherally mediated. We conclude theobromine is a novel and promising treatment, which may form the basis for a new class of antitussive drugs.

Development of a new method for simultaneously evaluating mucociliary clearance and pulmonary epithelial permeability in rabbit experiments by means of 18FDG, three-dimensional positron emission tomography and rectilinear scan

We tried to simultaneously obtain the elimination constant of mucociliary clearance and the pulmonary epithelial permeability constant after inhalation of 2-[18F]fluoro-2-deoxy-D-glucose (18FDG) solution by carrying out whole lung positron emission tomography and a rectilinear scan in rabbit experiments. The elimination constant of pulmonary epithelial permeability was obtained from the decrease in the amount of the radioactivity with time in the region of interest (ROI) confined to the lungs, trachea and tracheal cannula in the rectilinear scan. The total elimination constant of the radioactivity in the lungs was obtained from the ROI confined to the lungs in the tomography. The mucociliary clearance rate constant in the lungs was then obtained after subtracting the elimination constant of the pulmonary epithelial permeability from the total elimination constant of the 18FDG in the lungs. The mucociliary clearance constant in the trachea was calculated from the residual radioactivity in the trachea and the mucociliary clearance constant in the lungs. The mean pulmonary epithelial permeability constant was 0.0020% min(-1) obtained from the rectilinear scan. The mean mucociliary clearance constants of the lungs and the trachea were 0.0006 and 0.025% min(-1), respectively. These results indicated that the pulmonary epithelial permeability and mucociliary clearance could be evaluated simultaneously with 18FDG by using three-dimensional positron emission tomography and a rectilinear scan.

Nasal mucociliary clearance as a factor in nasal drug delivery

The nasal mucociliary clearance system transports the mucus layer that covers the nasal epithelium towards the nasopharynx by ciliary beating. Its function is to protect the respiratory system from damage by inhaled substances. Impairment of nasal mucociliary clearance can result in diseases of the upper airways. Therefore, it is important to study the effects of drugs and drug excipients on nasal mucociliary clearance. A large number of methods are used to assess mucociliary clearance. These methods study the effects of drug and excipients on the mucociliary system in vitro or in vivo in animals and humans. In some cases, the results of different in vitro and in vivo measurements do not correlate well. In vitro methods, especially ciliary beat frequency measurements, have been demonstrated to be valuable tools for toxicity screening. However, in vivo studies are essential to confirm the safety of nasal drug formulations. Nasal mucociliary clearance also has implications for nasal drug absorption. Drugs are cleared rapidly from the nasal cavity after intranasal administration, resulting in fast systemic drug absorption. Several approaches are discussed to increase the residence time of drug formulations in the nasal cavity, resulting in improved nasal drug absorption. However, more experimental evidence is needed to support the conclusion that this improved absorption is caused by a longer residence time of the nasal drug formulation.

Effects of xanthine derivatives on phosphatidylcholine secretion in primary culture of rat type II pneumocytes

Xanthine derivatives, pentoxifylline, aminophylline, theophylline and chinoin-170, increased phosphatidylcholine secretion in a primary culture of rat type II pneumocytes. However, these xanthines alone had no effect on intracellular cAMP levels in type II pneumocytes. In contrast, terbutaline-induced secretion of phosphatidylcholine was augmented by these xanthines, and the augmentation depended on the increase of cAMP levels. These results suggest that the xanthines induce phosphatidylcholine secretion possibly through cAMP-dependent and cAMP-independent pathways in the primary culture of rat type II pneumocytes.

Ciliary beat frequency at six levels of the respiratory tract in cow, dog, guinea-pig, pig, rabbit and rat

1. The ciliary beat frequency (CBF) of six animal species from six regions of the respiratory tract were measured: inferior turbinate, nasopharynx, the upper part of trachea from first to second cartilage, the lower part of trachea, main bronchus and subsegmental bronchi. Cow, pig, dog, rabbit, guinea-pig and rat were studied. 2. There were no significant differences in the CBF values between cow, pig and dog, and the ciliary activity was essentially the same (11.3-16.9 Hz) in all parts of the respiratory tract. 3. In the rat, the CBF was slower, especially in subsegmental bronchi (6.8 Hz). 4. In general, CBF was higher in upper than lower airways, with the exception of guinea-pig. 5. Signal quality was the highest in guinea-pig tissue, whereas rat tissue produced the signal with the widest variation in CBF and the highest proportion of distorted waveforms. 6. Therefore, for studying drug effects on ciliary activity, guinea-pig seems to be a more suitable animal than the more commonly used rabbit or rat. In drug comparisons, the same part of the respiratory tract and the same animal species should be used.