What is the dose of aspirin that should be administered and for how long do we have to give aspirin-?

Depends on use: The usual dose for headache or minor pains is 1-2 325mg tablets every 4 hours for up to 12 tablets in one day. But watch for stomach upset, bleeding, or ulcer disease. For middle age cardiovascular event/ tia/stroke prevention, 75-325mg (baby Aspirin to regular dose aspirin) is recommended. For acute heart syndrome or chest pain of possible heart attack, chew 325mg tablet (tastes bitter, but ok).