I have been taking acyclovir for 3 weeks now due to shingles outbreak from a broken rib, was feeling

Firstly, I would highly recommend that you look at the following on this site:
http://www.drugs.com/search.php?searchterm=Acylovir

Secondly, I would also highly recommend that you discontinue the beer and start keeping track (including the date of the 2 beers and subsequent flare up) so you can tell your doctor what is happening. Your doctor may be able to answer this question better than any of us.

When it comes to interactions, this site has a valuable tool ... add all your medications to it and your conditions and it tells you important information about the drug Acyclovir. Sometimes there is information as well about food if there is a mild, moderate or severe interaction with the drug.

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Shingles are a b***h! I've had them 3 times in my life; once when I was 13, and twice two years ago. I personally recommend strongly that you don't mess around in any way (with dosage, frequency, duration of taking the medicine as well as anything that makes the shingles worse, such as, in your case beer) with this medicine. I was told by my doctor (not advice to you, but to me) that after the second treatment of the same outbreak the Acyclovir would no longer work and I could suffer from shingles for the rest of my life! I looked it up online and found some validation of that concept. Just a warning.

You're doing a good thing; paying attention. The most important part of treatment. Much luck to you, and don't be afraid to use this site's tools to help you make decisions with your doctor's input ... and you can even report side effects to the FDA... about your medication.