I've taken amoxicillin trihydrate 500mg for tooth infection(3 caps/day), how long does it stay in my body?

The drug or infectio: The infection could be gone but can come back. That's why you need to finish your course of medication.

2-3 days: Amoxicillin starts to break down in your body after bout 1 hour. So to maintain maximum dosage levels you take it 3 x per day. When you are finished your course of antibiotics , it takes about 2-3 days for all traces of it to disappear.

Half life 61 minutes: The half life of Amoxicillin is about 61 minutes . This means that after a single dose every 61 minutes half of the drug is gone until undetected. This is why there is a 3-4x daily dosage to make sure there is adequate blood concentration to fight he bacteria.