Anti tubercular drugs like Isonex,rifampicin
and pyrizinamide are hepatotoxic and can cause nausea
.you must get liver function tests done and if transaminases like SGOT and SGPT are more three times the normal limit ,then they are stopped and rechallenged again after the liver enzymes become normal.If liver enzymes are normal or raised slightly,then you may add a proton pump
inhibitor like PANTOPROZOLE 40 mg empty stomach in the morning.This should settle he vomiting.Gradually body gets used to anti tubercular medicines and person becomes all right.
You should keep getting liver function tests done on regular basis to see for hepatotoxicity