I took mucofen for bronchitis, and within one hour of taking the pill, my heart was racing (resting heart rate of 95 when I am normally 55-60). I was jittery, anxious, restless, felt just miserable. I didn't take any more of the medicine, but it took a full 24 hours to wear off. I do tend to have very strong reactions to medication, but this was very distressing. Use with caution.