Treatment of latent TB is an important aspect of TB control in the United States, but the effectiveness of this strategy is compromised by patients' lack of commitment to follow the recommended 9-month cycle of isoniazid therapy. American researchers compared the frequency of course completion and the development of adverse drug reactions in patients who received isoniazid for 9 months or rifampicin for 4 months for latent TB.

From January 1999 to January 2004, 2,255 patients with latent tuberculosis were analyzed retrospectively. The study included 770 patients who received isoniazid for 9 months and 1,379 patients who were prescribed rifampicin with a 4-month course. At least 80% of the prescribed treatment was received by 52.6% of the patients in the isoniazid group and 71.6% in the rifampicin group (p = 0.001).

Analysis using multiple logistic regression showed that the treatment regimen was independently associated with the probability of completing complete treatment - for example, the probability of ending treatment with rifampicin was 2.88 times higher than isoniazid.

The undesirable effects which led to discontinuation of treatment with the studied medicinal products developed in 4.6% of patients in the isoniazid group and in 1.9% of patients in the rifampicin group (p = 0.001). Among the most commonly reported NLRs, hepatotoxicity, rash, gastrointestinal disturbances, thrombocytopenia or fatigue were noted. Compared with the rifampicin group, in the isoniazid group, hepatotoxicity phenomena were more often recorded (1.8% vs 0.08%; p = 0.001).

The authors conclude that, compared to a 9-month isoniazid treatment, a 4-month rifampicin treatment was characterized by a higher percentage of patients completing treatment and a smaller number of patients with clinically undesirable drug reactions.

The disadvantages of the study are the retrospective design, the lack of randomization, the possible presence of other interfering factors, as well as the fact that the examination of the presence of a hepatic pathology during the initial visit and the follow-up of hepatotoxicity during treatment were not unified. According to the design of this study, it cannot be excluded that patients who did not attend the follow-up visits could not do so due to the development of adverse drug reactions which were not taken into account thereafter.

The authors believe that it is necessary to conduct prospective studies on the efficacy and economic feasibility of rifampicin treatment, as well as to determine the risk of developing acquired resistance to rifampicin if treatment fails.