The doxy for your dog does degrade to a toxic form after expiration....can potentially damage your kidneys.
Don't really have anything bad to say about the Z pak.....seems to be what the doc gives me on the very rare occasion I go to the doc. Newer studies show it may have damaging effects on the heart, but if you think you're dying of something else I guess that really doesn't matter.
IANADOC, lol
Z-packs have been so over used it may not be as effective anymore.