[Clinical evaluation of new quinolones as antituberculosis drugs]

Compared with the recent rapid advances in the diagnosis of tuberculosis, advances in the treatment of tuberculosis have been quite slow. For example, as long as six months are required for initial treatment, even with addition of pyrazinamide in the first two months to isoniazid, rifampicin, and streptomycin or ethambutol. Moreover, it is not always easy to treat patients who cannot receive standard agents including isoniazid and rifampicin due to adverse effects of these drugs or drug resistance. For these reasons, the development of new agents with potent antituberculosis activities and fewer adverse effects is urgently desired. However, at present, few new antituberculosis agents are being developed, and new quinolones are considered the most promising new antituberculosis agents due to their lack of cross-resistance to previously existing antituberculosis agents, their excellent in vitro and in vivo antituberculous activities, and good pharmacokinetics. We therefore reviewed experimental studies and clinical reports useful for evaluation of potential clinical use of new quinolones as antituberculosis drugs. Our conclusions are summarized below: 1) Of nine new quinolones on the market, ofloxacin, ciprofloxacin, aparfloxacin and levofloxacin have excellent in vitro and in vivo antituberculous activities without cross-resistance to previously existing antituberculosis agents. 2) Ofloxacin appears to be useful clinically for intractable multidrug-resistant tuberculosis. The incidence and severity of adverse effects of ofloxacin were very low on longterm administration. 3) Ofloxacin resistance emerged from two to four months after initiation of administration of ofloxacin, and ofloxacin exhibited cross-resistance to other new quinolones. 4) The usefulness of new quinolones for initial treatment of tuberculosis is unclear. 5) New quinolones should be used to treat patients with drug-resistant tuberculosis and those patients for whom adverse effects have limited the use of standard agents. However, monotherapy with new quinolones is not recommended, due to the significant risk of emergence of quinolone resistance. 6) Not only ofloxacin, ciprofloxacin, sparfloxacin and levofloxacin, which are on the market, but also gatifloxacin, CS-940, Du-6859a and other newly developed new quinolones are candidates for new antituberculosis agents. However, careful study not only of antituberculous activities and pharmacokinetic but also drug interactions and chronic cumulative toxicities due to long-term administration are needed prior to clinical application of these drugs.