I was prescribed Mucinex D for acute sinus infection, along with an anti-biotic, and steriod nose spray. I am experiencing the insomnia others are talking about, but I am wondering if Mucinex D causes cough. I am not coughing during the day at all (even after a morning dose of Mucinex D, only at night when I'm trying to sleep). At night, after an evening dose around 7 pm, a cough sets in around 9 or 10 pm. Thinking it was the nose spray, I didn't take it, only to have th cough start again (after taking Mucinex D). I have taken the antibiotic before and had no side effects.