Old and new drugs for the treatment of tuberculosis in children.

During the first 2 days of the 2-month intensive phase of tuberculosis treatment, isoniazid kills 90% of viable bacilli; this renders the patient non-infectious and reduces the risk of drug resistance. Already, during this phase, pyrazinamide contributes to sterilisation or the prevention of relapse, and ethambutol or streptomycin prevent drug resistance developing. During the 4-month continuation phase, rifampicin kills the last remaining bacilli while isoniazid assists in preventing drug resistance. For paucibacillary childhood tuberculosis, a three-drug intensive phase is sufficient. The lesions of childhood tuberculosis often respond slowly, but this does not imply that treatment should be prolonged. Young children are exposed to lower serum concentrations of antituberculosis agents than are adults receiving equivalent doses and should receive doses at the higher end of recommended ranges. For the first time in three decades, new antituberculosis agents have entered clinical trials, but it may be several years before their evaluation is complete.