First round antibiotics not completely working for sinus infection, how soon after last dose do i wait to get a second round?

Tough question: to answer. first thing to figure out is if you truly need antibiotics (IDSA has guidelines helpful in differentiating bacterial from viral sinusitis), second question is were you on the appropriate antibiotic for the appropriate duration, and finally is there some reason why you aren't clearing the infection. a visit with a good physician is irreplaceable.