WOAH! Hold up, amigo. DO NOT stop taking antibiotics in the middle of a dose!! That is how highly-resistant superbugs develop (infections that are resistant to whole categories of antibiotics). The doctor prescribes you a certain round, 7-14 days typically depending on the problem. If you stop taking it a couple of days early, only the very strongest of the bacteria in your body have survived since the weaker ones would have been killed in the first couple of days of antibiotics. Only the most resistant ones survive to the end of the round of meds. Now, these very strong and resistant bacteria are free to multiply, creating millions of bacteria in your body that are just as strong and resistant. You will not only remain sick, but may find that this kind of antibiotic doesn't work for you in the future, which knocks one off your list. For example, maybe amoxicillin would work best for Person A's type of infection, but now that she is resistant to amoxicillin, it won't work for her, and it's possible that all of the antibiotics in its family like piperacillin and floxacillin won't either. If this happens, the types of antibiotics she can take in the future decreases. This doesn't sound dangerous since there are many types of antibiotics out there, but certain antibiotics work better for certain infections. Some have horrible side effects. Some are hard to access. One day you may be in an isolated area that only has specific types available (this one is bigger if you travel in developing nations or rural areas). You may have severe sensitivities to some kinds of antibiotics. There are plenty of reasons why you don't want to be resisant!
What you would be doing by stopping taking antibiotics in the middle of the round would be giving these more resistant bacteria 24 hours to multiply. In that time, a HUGE number can multiply and fill your body. You have a few days worth of meds to take after you roll, but the dose will not be nearly enough to kill the amount that have multiplied. You would need to go back to your doctor to get a few days' more antibiotics to make up for the time you lost allowing those little suckers to divide like crazy! No bueno.
Out of all the medications out there, there are only a few that will absolutely not work if not taken as prescribed: Birth control, antibiotics, and certain psychiatric medications, mostly. Do not mess with it. I wouldn't ever recommend taking MDMA while on medications that could decrease your body's metabolism, but in my opinion, if you were going to roll no matter what anybody said, my opinion is that it would be safer to take the MDMA in a smaller dose (since your body will not break it down as quickly, a smaller dose would still get you just as high, theoretically) than it would be to stop taking your antibiotics, even for a day.
Stay safe!