Optimal Sampling Strategies for Therapeutic Drug Monitoring of First-Line Tuberculosis Drugs in Patients with Tuberculosis

BACKGROUND: The 24-h area under the concentration-time curve (AUC24)/minimal inhibitory concentration ratio is the best predictive pharmacokinetic/pharmacodynamic (PK/PD) parameter of the efficacy of first-line anti-tuberculosis (TB) drugs. An optimal sampling strategy (OSS) is useful for accurately estimating AUC24; however, OSS has not been developed in the fed state or in the early phase of treatment for first-line anti-TB drugs. METHODS: An OSS for the prediction of AUC24 of isoniazid, rifampicin, ethambutol and pyrazinamide was developed for TB patients starting treatment. A prospective, randomized, crossover trial was performed during the first 3 days of treatment in which first-line anti-TB drugs were administered either intravenously or in fasting or fed conditions. The PK data were used to develop OSS with best subset selection multiple linear regression. The OSS was internally validated using a jackknife analysis and externally validated with other patients from different ethnicities and in a steady state of treatment. RESULTS: OSS using time points of 2, 4 and 8 h post-dose performed best. Bias was < 5% and imprecision was < 15% for all drugs except ethambutol in the fed condition. External validation showed that OSS2-4-8 cannot be used for rifampicin in steady state conditions. CONCLUSION: OSS at 2, 4 and 8 h post-dose enabled an accurate and precise prediction of AUC24 values of first-line anti-TB drugs in this population. TRIAL REGISTRATION: ClinicalTrials.gov (NCT02121314)

Sensitivity and specificity of routine diagnostic work-up for tuberculosis in lung clinics in Yogyakarta, Indonesia: a cohort study

BACKGROUND: Establishing a correct diagnosis is challenging. We aimed to investigate the sensitivity and specificity of routine tuberculosis (TB) diagnostic work-up in lung clinics in Indonesia, a country with the third highest TB burden and the second highest gap between notifications of TB cases and the best estimate of incident cases in the world. METHODS: In the lung clinics of the Province of Yogyakarta, Indonesia, we recruited all consecutive patients with symptoms suggesting TB, aged ≥18 years. Routine TB examination consisted of clinical evaluation, sputum smear microscopy, and chest radiography. For research purposes, we added sputum culture, Human Immunodeficiency Virus (HIV) testing, and follow-up for 1.5 years or 2.5 years if culture results disagreed with the initial clinical diagnosis. The initial diagnosis was considered incorrect if patients did not respond to treatment. We calculated sensitivity and specificity of the TB routine examination using culture and a composite reference standard (CRS - a combination of routine examination, culture, and follow-up) as the reference standards. All analyses were conducted with IBM SPSS Statistics 25 (IBM Corp., Armonk, NY, USA). RESULTS: Between 2013 and 2015, we included 360 participants, and 21 were excluded due to incomplete data. Among those analyzed, 115 were initially diagnosed with smear-positive TB, 12 with smear-negative TB, and 212 non-TB. In 15 study participants, the diagnosis was changed after median 45 (range: 14-870) days; 14 participants initially not diagnosed with TB were later diagnosed with TB, while one subject initially diagnosed with TB actually did not have TB. Compared with culture and CRS, TB routine examination had sensitivity of 85% (95%CI: 77-91) and 90% (95%CI: 84-94), and specificity of 86.3% (95%CI: 81-91) and 99.5% (95%CI: 97-100), respectively. CONCLUSIONS: A combination of clinical evaluation with sputum microscopy and chest radiography provided high sensitivity and specificity in diagnosing TB in lung clinics; in only 4.4% the diagnosis was incorrect. There is a need to improve routine TB diagnostic work by using clinical evaluation, sputum smear microscopy, and chest radiography all together in other settings, such as in primary health centers. TRIAL REGISTRATION: NCT02219945 , clinicaltrials.gov . Registered 19 August 2014 (retrospectively registered)

Impact of food intake on pharmacokinetics(PK) of first-line tuberculosis drugs in treatment-naive patients

Background: In treatment naive TB patients, the impact of food intake on the PK data of 1st line TB drugs is unknown in the early phase of treatment. Objectives: To assess impact of food intake on PK of isoniazid(INH), Rifampisin(RIF),pyrazinamide(PZA)and ethambutol(EMB) in treatment-naive TB patients. Methods: Randomized, cross-over trial in 20 patients. Subjects were administered INH, RIF, and EMB iv and PZA orally on day 1,and Fixed Drug Combination of all four on day 2&3 either while fasting or along with a high carbohydrate meal. Full PK curves were collected, and assayed by Liquid Chromatography-tandem Mass Spectrometry. Results: mean age was 41.8(SD=20)yrs, mean body mass index 17.48(SD=2.6)kg/m2. The PK data was shown in Conclusions: In treatment naive TB patients, concomitant food intake substantially influenced PK of TB drugs. Area under the curve(AUC0-24,),maximum concentration(Cmax ) and bioavailability decreased significantly when drugs were taken with food. The impact of the differences found in drug exposure on treatment efficacy and tolerability should be evaluated in a randomized prospective study. (Table Presented)

Impact of food on the pharmacokinetics of first-line anti-TB drugs in treatment-naive TB patients: a randomized cross-over trial

Concomitant food intake influences pharmacokinetics of first-line anti-TB drugs in healthy volunteers. However, in treatment-naive TB patients who are starting with drug treatment, data on the influence of food intake on the pharmacokinetics are absent. This study aimed to quantify the influence of food on the pharmacokinetics of isoniazid, rifampicin, ethambutol and pyrazinamide in TB patients starting anti-TB treatment. A prospective randomized cross-over pharmacokinetic study was conducted in treatment-naive adults with drug-susceptible TB. They received isoniazid, rifampicin and ethambutol intravenously and oral pyrazinamide on day 1, followed by oral administration of these drugs under fasted and fed conditions on two consecutive days. Primary outcome was the bioavailability while fasting and with concomitant food intake. This study was registered with clinicaltrials.gov identifier NCT02121314. Twenty subjects completed the study protocol. Absolute bioavailability in the fasted state and the fed state was 93% and 78% for isoniazid, 87% and 71% for rifampicin and 87% and 82% for ethambutol. Food decreased absolute bioavailability of isoniazid and rifampicin by 15% and 16%, respectively. Pyrazinamide AUC(0-24) was comparable for the fasted state (481 mg center dot h/L) and the fed state (468 mg center dot h/L). Food lowered the maximum concentrations of isoniazid, rifampicin and pyrazinamide by 42%, 22% and 10%, respectively. Time to maximum concentration was delayed for isoniazid, rifampicin and pyrazinamide. The pharmacokinetics of ethambutol were unaffected by food. Food decreased absolute bioavailability and maximum concentration of isoniazid and rifampicin, but not of ethambutol or pyrazinamide, in treatment-naive TB patients. In patients prone to low drug exposure, this may further compromise treatment efficacy and increase the risk of acquired drug resistance