Foster Kitten with URI

[Chama]

I just got a new foster kitten and he just completed a round of antibiotics (amoxicillin I believe) He still sounds congested but it almost seems like he can't quite pass the last of the mucus.

I am not sure if this means that the infection is still there or if it is just the afteraffects. Obviously if this continues I will take him to the vet in a day or two but in the meantime does anyone have anything that helps pass some of the mucus.

He seems good other than that (eating, drinking & playing) and quite a bit of energy.

Thanks for your help!