Rifampicin, isoniazid, ethambutol, ethionamide, and streptomycin in murine tuberculosis: comparative chemotherapeutic studies

Evaluation of high-dose rifampin in patients with new, smear-positive tuberculosis (HIRIF): study protocol for a randomized controlled trial

Background

Evidence has existed for decades that higher doses of rifampin may be more effective, but potentially more toxic, than standard doses used in tuberculosis treatment. Whether increased doses of rifampin could safely shorten treatment remains an open question.

Methods/Design

The HIRIF study is a phase II randomized trial comparing rifampin doses of 20 and 15 mg/kg/day to the standard 10 mg/kg/day for the first 2 months of tuberculosis treatment. All participants receive standard doses of companion drugs and a standard continuation-phase treatment (4 months, 2 drugs). They are followed for 6 months post treatment. Study participants are adults with newly diagnosed, previously untreated, smear positive (≥2+) pulmonary tuberculosis. The primary outcome is rifampin area under the plasma concentration-time curve (AUC_0–24) after at least 14 days of study treatment/minimum inhibitory concentration. 180 randomized participants affords 90 % statistical power to detect a difference of at least 14 mcg/mL*hr between the 20 mg/kg group and the 10 mg/kg group, assuming a loss to follow-up of up to 17 %.

Discussion

Extant evidence suggests the potential for increased doses of rifampin to shorten tuberculosis treatment duration. Early studies that explored this potential using intermittent, higher dosing were derailed by toxicity. Given the continued large, global burden of tuberculosis with nearly 10 million new cases annually, shortened regimens with existing drugs would offer an important advantage to patients and health systems.

Trial registration

This trial was registered with clinicaltrials.gov (registration number: NCT01408914) on 2 August 2011.

In vitro bactericidal and in vivo therapeutic activities of a new rifamycin derivative, KRM-1648, against Mycobacterium tuberculosis

The in vitro and in vivo activities of a new rifamycin derivative, KRM-1648, against Mycobacterium tuberculosis H37Rv were compared with those of rifampin. Bactericidal activity was evaluated by using a silicone-coated slide culture method. The MBC of KRM-1648 was 0.15 to 0.3 microgram/ml for 24 h of exposure, while that of rifampin was > 160 microgram/ml under the same conditions. Against experimental murine tuberculosis, KRM-1648 exhibited significant therapeutic effects, in terms of prolonged survival times for mice compared with those with rifampin treatment, even at lower doses, such as 1 and 3 mg/kg. At a dose of 3 mg/kg, KRM-1648 was at least as effective as rifampin at 10 mg/kg. The combination of KRM-1648 (3 mg/kg) plus isoniazid (3 mg/kg) plus ethambutol (10 mg/kg) exhibited much more activity than did rifampin (10 mg/kg) plus isoniazid (3 mg/kg) plus ethambutol (10 mg/kg). These findings suggest that KRM-1648 is a promising candidate for the treatment of tuberculosis.

In vitro and in vivo activities of the nitroimidazole CGI 17341 against Mycobacterium tuberculosis

CGI 17341 (2-ethyl-5-nitro-2,3-dihydro[2-1b]imidazo-oxazole) is a novel orally active representative of the 5-nitroimidazole series of antimicrobial agents. At concentrations ranging from 0.1 to 0.3 micrograms/ml, CGI 17341 inhibited the drug-susceptible and multi-drug-resistant strains of Mycobacterium tuberculosis. CGI 17341 had no cross-resistance with isoniazid, rifampin, streptomycin, or ethambutol. While the in vitro activity of CGI 17341 against M. tuberculosis was comparable to those of isoniazid and rifampin, it was superior to those of streptomycin, ciprofloxacin or norfloxacin, and oxazolidinone DuP 721. The MIC of CGI 17341 was not affected when the pH of the medium was decreased from 6.8 to 5.6, while four- to sixfold increases in the MICs of ciprofloxacin and isoniazid were observed. In mice infected with M. tuberculosis, the 50% effective dose for CGI 17341 was 7.7 mg/kg of body weight (95% confidence limits, 3.5 and 10.27) when administered on days 11 and 12 postinfection. CGI 17341 gave a dose-dependent (r = 0.995) and significant increase in the survival time. Our data indicate that the 5-nitroimidazole CGI 17341 is a promising and novel antituberculosis compound with potent in vitro and in vivo activities. Further investigations on this compound are warranted.

A controlled trial of individually-adapted short-course chemotherapy versus two-year scheme in original treatment of pulmonary tuberculosis. Report after a five-year follow-up

Patients with culture-positive pulmonary tuberculosis were allocated at random into two groups for a three-phase regimen in original course chemotherapy. The first group was given rifampicin (RMP) plus isoniazid (INH) plus ethambutol until sensitivity tests were completed, then RMP plus INH until culture conversion, thereafter INH alone for four months. The second group received the same drugs until obtaining culture conversion, thereafter IHN alone for a period lasting two years after onset of chemotherapy. One hundred sixty-eight patients were available for the final assessment after a five-year follow-up after culture conversion. Two bacteriologic relapses occurred among the two-year scheme patients, none in the short-course patients.