New antibiotics for community-acquired lower respiratory tract infections: improved activity at a cost?

Opinions are changing as to the continued validity of traditional beta-lactam and macrolide therapy of community acquired LRTI, partly because of resistance and partly because of early evidence that suggests that some new agents may be more effective. Guidelines are altering to reflect this view, although there is conflicting evidence on their effects on outcome. Fluoroquinolones are becoming accepted in the treatment of community acquired pneumonia and are established choices for acute exacerbations of chronic bronchitis. The 8-methoxy fluoroquinolones, moxifloxacin and gatifloxacin, have excellent anti-pneumococcal activity and may become drugs of choice for penicillin/macrolide resistant infections. They appear free of the serious idiosyncratic reaction profiles, possibly related to the immunologically reactive 1-difluorophenyl substituent, which characterised the recently withdrawn temafloxacin, trovafloxacin and tosufloxacin. All quinolones so far tested appear to prolong the QTc interval, but only sparfloxacin and grepafloxacin caused clinical effects. Nevertheless, caution is required until this effect is fully investigated.