I had Achilles tendonitis in my left ankle during my cross country tour last year. It developed very early on. About 4 days into my 3+ month long tour. I still have it to this day. Some days it was really bad. When I flexed my ankle it sounded like a dry piston rubbing. It was nasty sound.

Anyway, my doctor gave me Meloxicam and I survived off of that the rest of my trip. Now when I bike I take any type of Naproxen. One in the morning and one at night. Even the generic store brand (50 for maybe $3) works well. And boy do I notice the days where I forget to take it. Remember that it takes 15-30 minutes for your body to absorb the medication so don't take it and get on the bike right away. It should be taken right away and by the time you're ready to break camp it'll be working.