L-arginine and vitamin D adjunctive therapies in pulmonary tuberculosis: a randomised, double-blind, placebo-controlled trial.

BACKGROUND: Vitamin D (vitD) and L-arginine have important antimycobacterial effects in humans. Adjunctive therapy with these agents has the potential to improve outcomes in active tuberculosis (TB). METHODS: In a 4-arm randomised, double-blind, placebo-controlled factorial trial in adults with smear-positive pulmonary tuberculosis (PTB) in Timika, Indonesia, we tested the effect of oral adjunctive vitD 50,000 IU 4-weekly or matching placebo, and L-arginine 6.0 g daily or matching placebo, for 8 weeks, on proportions of participants with negative 4-week sputum culture, and on an 8-week clinical score (weight, FEV1, cough, sputum, haemoptysis). All participants with available endpoints were included in analyses according to the study arm to which they were originally assigned. Adults with new smear-positive PTB were eligible. The trial was registered at ClinicalTrials.gov NCT00677339. RESULTS: 200 participants were enrolled, less than the intended sample size: 50 received L-arginine + active vitD, 49 received L-arginine + placebo vit D, 51 received placebo L-arginine + active vitD and 50 received placebo L-arginine + placebo vitD. According to the factorial model, 99 people received arginine, 101 placebo arginine, 101 vitamin D, 99 placebo vitamin D. Results for the primary endpoints were available in 155 (4-week culture) and 167 (clinical score) participants. Sputum culture conversion was achieved by week 4 in 48/76 (63%) participants in the active L-arginine versus 48/79 (61%) in placebo L-arginine arms (risk difference -3%, 95% CI -19 to 13%), and in 44/75 (59%) in the active vitD versus 52/80 (65%) in the placebo vitD arms (risk difference 7%, 95% CI -9 to 22%). The mean clinical outcome score also did not differ between study arms. There were no effects of the interventions on adverse event rates including hypercalcaemia, or other secondary outcomes. CONCLUSION: Neither vitD nor L-arginine supplementation, at the doses administered and with the power attained, affected TB outcomes. REGISTRY: ClinicalTrials.gov. Registry number: NCT00677339.

Pharmacokinetics of L-arginine in adults with moderately severe malaria.

Severe malaria is associated with decreased nitric oxide (NO) production and low plasma concentrations of L-arginine, the substrate for NO synthase. Supplementation with L-arginine has the potential to improve NO bioavailability and outcomes. We developed a pharmacokinetic model for L-arginine in moderately severe malaria to explore the concentration-time profile and identify important covariates. In doses of 3, 6, or 12 g,L-arginine was infused over 30 min to 30 adults with moderately severe malaria, and plasma concentrations were measured at 8 to 11 time points. Patients who had not received L-arginine were also assessed and included in the model. The data were analyzed using a population approach with NONMEM software. A two-compartment linear model with first-order elimination best described the data, with a clearance of 44 liters/h (coefficient of variation [CV] = 52%) and a volume of distribution of 24 liters (CV = 19%). The natural time course of L-arginine recovery was described empirically by a second-order polynomial with a time to half recovery of 26 h. The half-life of exogenous L-arginine was reduced in patients with malaria compared with that for healthy adults. Weight and ethnicity were significant covariates for clearance. MATLAB simulations of dosing schedules for use in future studies predicted that 12 g given over 6, 8, or 12 h will provide concentrations above the K(m) of endothelial cell CAT-1 transporters in 90%, 75%, and 60% of patients, respectively.

Therapeutic efficacies of artesunate-sulfadoxine-pyrimethamine and chloroquine-sulfadoxine-pyrimethamine in vivax malaria pilot studies: relationship to Plasmodium vivax dhfr mutations.

Artemisinin-derivative combination therapies (ACT) are highly efficacious against multidrug-resistant Plasmodium falciparum malaria. Few efficacy data, however, are available for vivax malaria. With high rates of chloroquine (CQ) resistance in both vivax and falciparum malaria in Papua Province, Indonesia, new combination therapies are required for both species. We recently found artesunate plus sulfadoxine-pyrimethamine (ART-SP) to be highly effective (96%) in the treatment of falciparum malaria in Papua Province. Following a preliminary study of CQ plus sulfadoxine-pyrimethamine (CQ-SP) for the treatment of Plasmodium vivax infection, we used modified World Health Organization criteria to evaluate the efficacy of ART-SP for the treatment of vivax malaria in Papua. Nineteen of 22 patients treated with ART-SP could be evaluated on day 28, with no early treatment failures. Adequate clinical and parasitological responses were found by day 14 in all 20 (100%) of the patients able to be evaluated and by day 28 in 17 patients (89.5%). Fever and parasite clearance times were short, with hematological improvement observed in 70.6% of the patients. Double (at positions 58 and 117) and quadruple (at positions 57, 58, 61, and 117) mutations in the P. vivax dihydrofolate reductase (PvDHFR) were common in Papuan P. vivax isolates (46 and 18%, respectively). Treatment failure with SP-containing regimens was significantly higher with isolates with this PvDHFR quadruple mutation, which included a novel T-->M mutation at residue 61 linked to an S-->T (but not an S-->N) mutation at residue 117. ART-SP ACT resulted in a high cure rate for both major Plasmodium species in Papua, though progression of DHFR mutations in both species due to the continued use of SP monotherapy for clinically diagnosed malaria threatens the future utility of this combination.