As you stated that you got PARASITIC infection
in Mexico , so advised 800 mg metroniazole three times in day .
Most probabaly you are feeling nausea, dizziness
, vomiting , abdominal discomfort , metallic taste
in mouth , as these are common side effect.
So when such situation arise I prescribe pantoprazole
-D two times in day with metronidazole
as this will subside these side effects of metronidazole .
Also antacid help in this case.
Take these dosage after meal .
In my opinion the optimum dosage is important . If you take reduced dosage at your own will then resistance may develop ( for parasitic infection).
So get full advised dosages or consult your treating doctor and get his opinion .
Hope this will help you.