Thanks for writing your query.
It might be a possibility that in addition to amoebiasis
, your nephew is also suffering from bacterial infection. Get his stool examined. If there is evidence of pus cells in report, it indicates bacterial infection. For that antibiotic should be added for relief of symptoms. Metronidiazole will help only in amoebiasis and not bacterial infeciton.
Nausea and loss of apetite can be a due to side effect of metronidiazole as it has metallic taste
.For pain you can give dicycloverine
after consultation with his Paeditrician.
Also get his blood test
for LFT ( Liver Function Test) and Complete Blood Count
I hope this is helpful to you.