Medicine for kiddos

My 2 year old and 4 year old are getting over a crud, they currently have a bad cough now from it all. I went out and bought some medicine that was already recommended to me, but it makes no sense and doesn't seem to work. This is from the website but it states the same on the box and bottle.

So they can basically only take it twice a day. Which doesn't help at all. Yeah it works for maybe a little bit but then they're coughing again by afternoon (if given in the morning), and then again in the evening (which is when we have been giving the 2nd dose).

I'll be taking them to the pediatric urgent care when they open since I can't get them in with their actual clinic.

So anyways, my question is do any of you mommas have any other recommendations on medicine?? I've never been a fan of zarbess as it is, but our stores are running slim on medicine 😩 I'm also already doing other natural stuff to help in the mean time