My Grandson 3months And 20 Days (wt. 5.8 Kg) Was

My grandson 3months and 20 days (wt. 5.8 kg) was given levolin syrup 1.25 ml each yesterday afternoon and today morning for cough as advised by a doctor. After giving it, on both occasions it is seen he is coughing somewhat continuously for about 15-20 minutes. Afterwards it decreases and coughs only occasionally. May I know why vigorous cough immediately after giving the medicine ? Kindly advise.

SASIDHARA KURUP