considering that doxycycline is a moderate CYP3A4 inhibitor and doesnt inhibit any other enzymes, the risk of interaction between the two drugs is probably low IMO but i am also no doctor or chemist or pharmacist though. there hasnt been any studies on antibiotics and mdma so theres no way to know for sure. the CYP2D6 is the main enzyme that breaks down mdma to my knowledge, not CYP3A4. i know of ppl who have rolled on antibiotics (but not doxycycline) and had a blast. then again they ended up being sick for a much longer period of time after they did that and were put on heavier antibiotics. probably not the best idea but it has been done before. i remember seeing a thread on this in the archive i will try to find it. id say its probably not worth it but u make ur own decisions. if u do it just be cautious...ur body is weak so dont overexert yourself, take less than u normally would, hydrate properly, be safe.