I am glad you posted this, even though it's a natural chicken keeping forum. We all care for our chickens differently, and what we share is a desire to keep things as natural as possible. Just like in our own lives, I would imagine!! But, just like in our own lives, sometimes natural doesn't cut it, and without standard medical intervention like antibiotics we'd end up with a dead chicken.
For some people, a naturally-treated dead chicken is preferable to a live one that's been treated with antibiotics (and I understand that view), but not for all of us. For me, I'd rather have a live chicken, especially if she were my favorite. I'd just not eat the eggs for a few weeks. If she died, with or without treatment with antibiotics, I couldn't eat her (or let my dog or the other chickens eat her) because my chickens are all pets - my kids would be mortified if I suggested eating them. Just like we wouldn't consider eating our dog if she died!
So, yes, I try to keep things as natural as possible, for the chickens' health, for our health, and for the world we live in. But I also think that there is a time and place for modern medicine.
Just like I don't judge anyone on this forum who eat your chickens, or who cull instead of treat a medical condition (to strengthen the health of the next generation, makes total sense), please don't anyone judge me or those of us who treat our chickens more like pets and would use medications as a last resort to save a favorite chicken's life.
Anyway, I just wanted to pipe up and say thank you for your post, which wasn't recommending giving penicillin to a bird you hadn't seen to treat a condition you didn't diagnose, but rather responding to someone's question about what dose to give. Dosages and routes of administration for different medicines for various species are published in tables, and are not considered a recommendation for treatment.
You also suggested a more natural treatment for egg yolk peritonitis, which was very cool. Thanks again!