We forgot to refrigerate augmentin (amoxicillin and clavulanate) suspension for a the first 16 hours for a 4 year old. ok to use?

Should be OK: It happens frequently and no one reports problems. Just do best to keep refrigerated.

Should be fine: These liquid preparations are usually good for about a week if left at air conditioned room temperature, 10-14 days in the fridge but can go bad if left out for a day or so in a hot vehicle. If you refrigerate it now it should be effective.