Is paracetamol can be a substitue for plan b?

No; more like Plan C: Paracetamol is more like a plan c (paracetamol is headache medicine that will treat the headache that comes from getting pregnant after not using plan b). First, a woman must decide what is the chance she could get pregnant. If the chance is high enough to worry her, then she can get Plan B at the drugstore. Plan b is not for a woman who is already pregnant. Her doctor can advise her properly.