The impact of alcohol and illicit substance use on the pharmacokinetics of first-line TB drugs.

BACKGROUND: In South Africa, an estimated 11% of the population have high alcohol use, a major risk factor for TB. Alcohol and other substance use are also associated with poor treatment response, with a potential mechanism being altered TB drug pharmacokinetics. OBJECTIVES: To investigate the impact of alcohol and illicit substance use on the pharmacokinetics of first-line TB drugs in participants with pulmonary TB. METHODS: We prospectively enrolled participants ≥15 years old, without HIV, and initiating drug-susceptible TB treatment in Worcester, South Africa. Alcohol use was measured via self-report and blood biomarkers. Other illicit substances were captured through a urine drug test. Plasma samples were drawn 1 month into treatment pre-dose, and 1.5, 3, 5 and 8 h post-dose. Non-linear mixed-effects modelling was used to describe the pharmacokinetics of rifampicin, isoniazid, pyrazinamide and ethambutol. Alcohol and drug use were tested as covariates. RESULTS: The study included 104 participants, of whom 70% were male, with a median age of 37 years (IQR 27-48). Alcohol use was high, with 42% and 28% of participants having moderate and high alcohol use, respectively. Rifampicin and isoniazid had slightly lower pharmacokinetics compared with previous reports, whereas pyrazinamide and ethambutol were consistent. No significant alcohol use effect was detected, other than 13% higher ethambutol clearance in participants with high alcohol use. Methaqualone use reduced rifampicin bioavailability by 19%. CONCLUSION: No clinically relevant effect of alcohol use was observed on the pharmacokinetics of first-line TB drugs, suggesting that poor treatment outcome is unlikely due to pharmacokinetic alterations. That methaqualone reduced rifampicin means dose adjustment may be beneficial.

Development and validation of a liquid chromatography tandem mass spectrometry assay for the analysis of bedaquiline and M2 in breast milk.

Objective: To develop and validate an assay for the analysis of bedaquiline and its M2 metabolite in human breast milk. Methods: The analytes were extracted using solid phase extraction following protein precipitation. Quantification was performed with liquid chromatography coupled with tandem mass spectrometry. Chromatographic separation was achieved using gradient chromatography on a Poroshell 120 SB-C18 analytical column at 40 °C, with a flow rate of 350 µL/minute and a total run time of eight minutes. An AB Sciex 3000 mass spectrometer with electrospray ionization in the positive mode was used for detection, employing multiple reaction monitoring scan mode. Bedaquiline-d6 and M2-d3-13C were used as internal standards. Results: Calibrations curves for bedaquiline and M2 exhibited quadratic (weighted 1/x concentration) regressions over the respective concentration ranges of 0.0780 to 5.00 µg/mL and 0.0312 to 2.00 µg/mL. Inter- and intra-day validation accuracies ranged between 96.7 % and 103.5 % for bedaquiline, and 104.2 % to 106.5 % for M2, with a coefficient of variation below 9.2 % for both compounds. Conclusion: The developed assay demonstrated selectivity and robustness, enabling differentiation between bedaquiline and M2 within the context of endogenous compounds from six separate lots of breast milk samples. Successful application was observed in the analysis of breast milk samples sourced from patients treated for multidrug-resistant tuberculosis within a clinical study setting.

Validation and application of an online extraction and liquid chromatography tandem mass spectrometry assay for the analysis of delamanid and its DM-6705 metabolite in human breast milk.

We developed and validated a bioanalytical assay to quantify delamanid and its key metabolite (DM-6705) in breast milk and aimed to quantify the secretion of these compounds in breast milk. Due to the hydrophobic nature of the analytes, special care was taken during sample preparation to prevent the formation of fatty deposits during protein precipitation. This was followed by online solid phase extraction and liquid chromatography with tandem mass spectrometry for detection. A Restek Viva BiPh C18 column (1.0 mm×50 mm, 5 µm) was used for extraction while chromatographic separation was performed using a Waters Xterra MS C18 (2.1 mm×100 mm, 5 µm) analytical column with an isocratic mobile phase consisting of acetonitrile, methanol, and 5 mM ammonium carbonate. The mass spectrometric detection of the analytes was performed using an AB Sciex 3200 mass spectrometer employing electrospray ionisation in the positive mode with multiple reaction motoring of the relevant precursor and product ions. Delamanid-d4 and OPC-14714 were used as internal standards. A quadratic (weighted 1/x concentration) regression was used to fit calibration curves for delamanid and DM-6705 over the concentration range of 10.0 - 1000 ng/mL. The intra- and inter-day validation accuracies of the quality control samples were between 92.1% and 98.3% for delamanid, and 97.0% and 102.8% for DM-6705. The percentage coefficient of variation (precision) was less than 7.8%. To our knowledge, this is the first report describing the concentrations of delamanid and DM-6705 in the breast milk of patients treated for rifampicin-resistant tuberculosis.