Posting for traffic. How long do antibiotics stay in your system? I had two yesterday for mastitis - one late afternoon, one in the evening. When I went to bed I was very tight chested, found it difficult to breath. I was then awake most of the night with palpitations and nausea, and now have diarrhoea - joy. I’ve requested a changeover to one I’ve taken before from the GP, how long until this one is out of my system? It’s awful 😣 for ted it’s Flucloxacillin.