The newer fluoroquinolones have broad-spectrum bactericidal activity, excel
lent oral bioavailability. good tissue penetration and favorable safety and
tolerability profiles. A new four-generation classification of the quinolo
ne drugs takes into account the expanded antimicrobial spectrum of the more
recently introduced fluoroquinolones and their clinical indications. First
-generation drugs (e.g.. nalidixic acid) achieve minimal serum levels. Seco
nd-generation quinolones (e.g.. ciprofloxacin) have increased gram-negative
and systemic activity. Third-generation drugs (e.g.. levofloxacin) have ex
panded activity against gram-positive bacteria and atypical pathogens. Four
th-generation quinolone drugs (currently only trovafloxacin) add significan
t activity against anaerobes. The quinolones can be differentiated within c
lasses based on their pharmacokinetic properties. The new classification ca
n help family physicians prescribe these drugs appropriately.