[Combination chemotherapy]

Although most cases of infections in humans with normal host defenses can be treated with a single antimicrobial agent today, there are several cases to whom combination chemotherapy should be adopted. Five reasons have been advanced to justify the use of antimicrobial combinations: prevention of the emergence of resistant organisms, control of polymicrobial infections, initial therapy when causative organism is unclear, appearance of synergism, and management of infections in immunocompromised host. But, a clear advantage has been difficult to demonstrate in vivo. Furthermore, inappropriate use of antimicrobial combinations may lead patients to antagonism, cost, and even adverse effects. Therefore, antimicrobial combination therapy requires careful evaluation prior to clinical use.