Efficacy of Two Doses of Duloxetine and Amitriptyline in Subjects With Refractory Chronic Cough

This is a randomized, double-blind, placebo-controlled, parallel-arm, dose escalation study of Duloxetine \& Amitriptyline in subjects with refractory chronic cough. Subjects will be screened during a period of up to 2 week and will undergo screening/ baseline cough monitoring. A total of 50 subjects who meet entry criteria will be randomly assigned in a 1: 1: 1: 1: 1 ratio to one of five treatment arms using stratified randomization in blocks of 10. Each arm will have two successive 4-week treatment periods (Blinded Period 1 \& 2). After this, patients will be unblinded and receive routine clinical care. During the unblinded (routine clinical care) follow up phase; subjects will be initially offered the option of continuing amitriptyline or duloxetine based on their initial randomization arm. Subjects could also choose an alternative chronic cough therapy (e.g. pregabalin, gabapentin, 1% tetracaine lollipop or nebulized lidocaine or combination therapy). Subjects in treatment arm 5, who received placebo during the 8 weeks blinded period will have a discussion regarding all available cough therapies. Patients will be offered the flexibility of therapy options during the unblinded follow up as they would during routine clinical care. Participation in the unblinded follow-up period will be optional. Treatment Arm 1: Blinded Period 1 (1st 4 weeks): 30mg of Duloxetine Blinded Period 2 (2nd 4 weeks): 30mg of Duloxetine \& 30mg of Placebo Unblinded (routine clinical care) follow up period: (up to 52 weeks): Subjects will be offered routine clinical care management for their chronic cough Treatment Arm 2: Blinded Period 1 (1st 4 weeks): 30mg of Duloxetine Blinded Period 2 (2nd 4 weeks): 60mg of Duloxetine (2 pills of 30mg each) Unblinded (routine clinical care) follow up period: (up to 52 weeks): Subjects will be offered routine clinical care management for their chronic cough Treatment Arm 3: Blinded Period 1 (1st 4 weeks): 25mg of Amitriptyline Blinded Period 2 (2nd 4 weeks): 25mg of Amitriptyline + 25mg of Placebo Unblinded (routine clinical care) follow up period: (up to 52 weeks): Subjects will be offered routine clinical care management for their chronic cough Treatment Arm 4: Blinded Period 1 (1st 4 weeks): 25mg of Amitriptyline Blinded Period 2 (2nd 4 weeks): 50mg of Amitriptyline (2 pills of 25mg each) Unblinded (routine clinical care) follow up period: (up to 52 weeks): Subjects will be offered routine clinical care management for their chronic cough Treatment Arm 5: Blinded Period 1 (1st 4 weeks): 30mg of Placebo Blinded Period 2 (2nd 4 weeks): 60mg of Placebo (2 pills of 30mg each) Unblinded (routine clinical care) follow up period: (up to 52 weeks): Subjects will be offered routine clinical care management for their chronic cough