Hi welcome to health care magic forum. From your quiry it is under stood that the vomiting
sensation could be due to the antibiotics or the disease systic fibrosis
, as it involves the liver
What ever the reason may be you can have relief of the feeling by using anti ulcerants and anti emitics, with the advise of your doctor.
Besides i advise you some diet recommendations as avoid taking spices, chillies, junk foods, and oily foods as these may increase the tendency to increase indigestion
and hence vomiting sensation.
Wishing for a quick and complete relief from the disease, and thanks for calling.