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Now a days deworming
is advised without even having symptoms ;the reason is the ova/cyst of worms
tend to remain in intestine
for a long time & in future can cause symptoms so as a precautionary measure deworming is done.As for the dose of medicines it is better given when the stomach empty either as the last thing to have at night & some even prefer as the first thing to have in morning.In both cases it is equally effective.