I have terrible viral tonsillitis and haven't been able to eat anything for 4 days. can i take a tylenol (acetaminophen) w/ codeine to ease the pain & stay hydrated?

Not advisable: to use narcotic medication for a very sore throat. You can use a combination of Advil or Aleve ( if not allergic) OR Tylenol (acetaminophen). I prefer zinc lozenges ( Cold-Eze Lozenges),warm water gargles and dark brown honey ( very soothing). Stay ahead on fluid intake and add electrolyte rich fluids like PowerAde. G, vitamin water to cold Jello.

Local is better.: While Tylenol (acetaminophen) with codeine would work, I'm sure, I would think that would be overkill for the treatment you seek. I'd rather see you use a local treatment, such as an over-the-counter anesthetic spray like Chloraseptic or something like that. You're already four days in, so this should be getting better on its own very soon. Don't overdo it.