Only very, very high doses of Claritin will kill the Lyme bacteria. Normal dose is 10 mgs and the dose for killing the Lyme bacteria are above 40 mgs a day (I don't remember the exact dose they were talking about
).
I use muccinex from time to time as well, but I've not noticed any herx like symptoms. What type of Muccinex are you using? There are several different types :
www.mucinex.com/social-support/drug-facts/The other thing you have to be aware of is that you could be reacting to one of the 'inactive' ingredients.