I took plan b 3days ago,i have a cold and my doctor gave me amoxicillin. will it effect the plan b?

Doubtful: The impact of antibiotic on contraceptive has always been controversial and I can think of no reason why it would affect Plan B. I do not think Amoxicillin or any antibiotic should be used for an uncomplicated cold since antibiotic does not affect virus and does have potential side effects.

Possibly: Because ampicillin can affect Plan B - It stands to reason that amoxicillin likely could as well. Antibiotics which can affect Plan B: ampicillin, cotrimoxazole (in Bactrim), Rifampin, tetracycline, & clarithromycin