When I was around 20/21 as well. I had developed bad side effects to Cipro and eventually resistance to it. I also found it wasn't really helpful to take anymore not sure if it was because of the thick mucus or what, but if I did take it it wasn't doing anything for me.
So, I was off and on IV's for my Multi-resistant pseudomonas from when I was 21 until I was 27/28ish. Then I got MRSA & it has over time pretty much taken over and overgrown my pseudomonas and so the only thing that is really bothering my lungs is the MRSA. My MRSA is sensitive to 3 different types of orals, so here I am at 30 able to take orals again.
Technically I'm still sensitive to Levaquin and Cipro, but they give me seizures, so I haven't been able to use orals since age 12. (I'm 19 now.)
Since then I've had several rounds of IVs, but I started working out a lot about a year ago and if I can just make it through the spring, I'll make it a year without IVs!