Treating a daytime cough, the (medicine) is probably no use. But trying some preparations to treat a nighttime cough is reasonable if it lets the family and kid sleep better. Chances are, it's not going to help.
Dr. Jeff Schunk quote
Be noble! And the nobleness that lies in other men, sleeping, but never dead, will rise in majesty to meet thine own
~ James Russell Lowell (February 22, 1819 - August 12, 1891)