Interventions
cough
At baseline, subjects with refractory cough who meet the inclusion and randomization criteria of this study and do not meet the exclusion criteria will be randomly assigned to the experimental drug group or the placebo group, and the experimental group will be given duloxetine hydrochloride enteric-coated tablets 20 mg, TID (starting with 20 mg QD, increasing 20 mg daily until 20 mg TID). The placebo group will receive placebo 20 mg, TID (started with 20 mg QD, increased 20 mg daily until 20 mg TID).