Can I Take Mucinex DM And Acyclovir Together Without Any Side Effect?

I'm currently taking the antibiotic Acyclovir for shingles. But not I currently have a horrible cough and cold. I took nyquil twice, finally figuring out that i was causing me to have an allergic reaction to the mix. Am I not supposed to mix those? And can I use Mucinex DM instead of the nyquil. I need to suppress my cough!