تعليقThe WHO guidelines recommend treating people with DS-TB with a 6-month regimen composed of four first-line TB medicines: isoniazid, rifampicin, pyrazinamide and ethambutol (1). The regimen is a combination of those four drugs (i.e. HRZE) for 2 months followed by isoniazid and rifampicin (i.e. HR) for 4 months, administered daily. In children (usually defined as being aged <10 years) in settings with a high background prevalence of isoniazid resistance or HIV infection, or in CLHIV, ethambutol should be used in the first 2 months of treatment; in all other situations ethambutol can be omitted, resulting in a 2HRZ/4HR regimen (20).
As a general rule, WHO does not recommend prolonging the regimen beyond 6 months (1), because there is evidence that prolongation does not significantly increase efficacy. The first 2 months of treatment, which includes four drugs, is usually enough for the strong bactericidal activity of this regimen to be effective. Thus, the presence of one or more sputum smear results that are still positive after 2 months usually indicates the presence of dead bacilli; however, in some cases, it might be due to undetected resistance to one or more drugs. If the patient is not improving clinically and radiologically, and drug-resistance or potential failure is suspected, rapid diagnostic testing to exclude these scenarios should be undertaken promptly, together with culture and DST, to provide a basis for any adjustment of the treatment strategy (22).
The systematic reviews on the dosages of the first-line medicines (rifampicin, isoniazid, ethambutol, and pyrazinamide) used in the treatment of drug-susceptible tuberculosis in adults and children were conducted. The reviews concluded that the WHO-recommended doses for rifampicin, isoniazid, ethambutol, and pyrazinamide remain valid in adults and children. (Web annex 1 and 2)