Morphine sulfate is an effective antitussive in intractable chronic cough at the doses of 5 to 10 mg twice daily.

Background: It has been proposed that the pH of airway lining fluid may regulate the fractional exhaled concentration of nitric oxide (FE NO ) in respiratory disease. Methods: FE NO , exhaled breath condensate (EBC) pH, and EBC concentrations of nitrite plus nitrate (NO 2 / NO 3 ) were compared in 12 subjects with stable asthma, 18 with stable cystic fibrosis (CF), and 15 healthy control subjects. Eight of the CF patients were studied on a separate occasion at the start of a pulmonary exacerbation. Results: FE NO was significantly greater in asthmatic subjects than in control subjects (mean 35 v 9 ppb, p,0.001). EBC pH, however, was similar in the asthmatic and control groups (median 5.82 v 6.08, p = 0.23). Levels of NO 2 /NO 3 were on average higher in EBC samples from asthmatic subjects, but the difference was not significant. In patients with stable CF both the FE NO (mean 4 ppb, p,0.001) and EBC pH (median 5.77, p = 0.003) were lower than in the control group. Levels of EBC NO 2 /NO 3 (median 29.9 mM; p = 0.002) in patients with stable CF, in contrast, were significantly higher than in control subjects. During CF exacerbations, EBC pH was further reduced (median 5.30, p = 0.017) but FE NO and NO 2 /NO 3 were unchanged.Conclusions: These findings demonstrate a dissociation between EBC pH and FE NO in inflammatory airways disease.

TRPV1 is a modulator of noxious stimuli known to be important in the cough reflex. We have compared the expression of TRPV1 in normal human airways and those from patients with chronic cough and found that there is up regulation in airways smooth muscle in disease. This increased expression appears to be intracellular and we have therefore examined the role of intracellular rat and human TRPV1 activity was found using intracellular calcium signalling with human intracellular TRPV1 being located in a thapsigargin insensitive compartment. Increase in TRPV1 activity may have a role in the airway hypersensitivity seen in chronic cough.

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