Lack of efficacy

The investigators hypothesise that cough reflex hypersensitivity, demonstrated in chronic cough patients, is due to a phenomenon known as central sensitisation. Central sensitisation is a hyper-excitability of the sensory nerves as they join the central nervous system, and is believed to be mediated by the N-Methyl-D-Aspartate (NMDA) receptor[1-3].

Inclusion Criteria:

• Male or female 18-75 years of age
• Females must be of non child-bearing potential
• Chronic Cough ( > 8 weeks)
• Normal Chest X-ray
• Normal Lung Function
• Idiopathic or treatment resistant cough-

Exclusion Criteria:

• Recent upper respiratory tract infection (<4 weeks)
• Pregnancy/breast-feeding
• Current smokers or ex-smokers with <6 months abstinence or cumulative history of >10 pack years
• Current treatment with ACE inhibitors.
• Drug or alcohol abuse
• Uncontrolled hypertension (i.e., >140/90 mmHg despite adequate medical therapy).
• Any cardiovascular condition that would be a contra-indication to the use of sympathomimetic amines (e.g. active angina).
• Any clinically significant neurological disorder
• Prior renal transplant, current renal dialysis.
• Any clinically significant or unstable medical or psychiatric condition that would interfere with the patient's ability to participate in the study.
• Increased risk of seizures.
• Any malignancy in the past 2 years (with the exception of basal cell carcinoma).
• Use of opioids, anticonvulsants, antidepressants (particularly MAO inhibitors).
• Any clinically significant abnormal laboratory test result(s).
• Serum creatinine laboratory value greater than 1.5 x upper limit of normal (ULN) reference range (after adjustment for age) or estimated creatinine clearance <60 mL/min.
• Total bilirubin greater than upper limit of normal reference range (with the exception of Gilbert's Syndrome) and/or alanine transaminase (ALT) >1.5 times upper limit of normal reference ranges (after adjustment for age).