Re: Why don't antibiotics work on viruses?

Antibiotics (biotic meaning bacteria) are natural or synthesized chemicals 
which inhibit or block metabolism of critical biologica functions of 
bacteria. Bacteria are free-living organisms who must use metabolic 
processes to acquire nutrients, digest them and synthesize membranes, 
organelles, cell wall and capsule. Some or all of these components may be 
present in all bacteria including pathogenic ones. A lot of antibiotics 
affect cell wall or capsule synthesis and others effect synthesis of 
proteins or enzymes the bacteria need to live.

Viruses, on the other hand, cannot continue living outside of the 
eukaryotic (animal, or plant) cells which they infect. Viruses must use 
the metabolic machinery of the host eukaryotic cell to replicate itself. 
Therefore, using a typical antibiotic rationale attempts to interfere with 
viral replication metabolism like described above for bacteria would make 
the host cells sick without necessarily harming the viruses. Since viruses 
are protein enveloped bits of DNA or RNA, most "antiviral" drugs are 
directed to metabolism of DNA or RNA but to be effective and safe these 
drugs must be targetted to DNA or RNA actions that are not normally used 
by the eukaryotic host cells. This is an extremely difficult task and many 
antiviral drugs make normal host cells pretty sick and there is an 
increased risk of serious (DNA/RNA) mutations, possibly leading to 
neoplasia that can result if antiviral drugs are used too much too long.

 http://www.soton.ac.uk/~gk/sc
ifi/virals.htm
 http://www.scrip
ps.edu/newsandviews/e_20020401/wong.html

I hope this is what you were looking for. I was on vacation when your 
question came in.