Safety of Rifampicin at High Dose for Difficult-to-Treat Tuberculosis: Protocol for RIAlta Phase 2b/c Trial

Critical illness due to infection in people living with HIV

People living with HIV comprise a substantial number of the patients admitted to intensive care. This number varies according to geography, but all areas of the world are affected. In lower-income and middle-income countries, the majority of intensive care unit (ICU) admissions relate to infections, whereas in high-income countries, they often involve HIV-associated non-communicable diseases diagnoses. Management of infections potentially resulting in admission to the ICU in people living with HIV include sepsis, respiratory infections, COVID-19, cytomegalovirus infection, and CNS infections, both opportunistic and non-opportunistic. It is crucial to know which antiretroviral therapy (ART) is appropriate, when is the correct time to administer it, and to be aware of any safety concerns and potential drug interactions with ART. Although ART is necessary for controlling HIV infections, it can also cause difficulties relevant to the ICU such as immune reconstitution inflammatory syndrome, and issues associated with ART administration in patients with gastrointestinal dysfunction on mechanical ventilation. Managing infection in people with HIV in the ICU is complex, requiring collaboration from a multidisciplinary team knowledgeable in both the management of the specific infection and the use of ART. This team should include intensivists, infectious disease specialists, pharmacists, and microbiologists to ensure optimal outcomes for patients.

Development and Validation of a UPLC-MS/MS Method for Therapeutic Drug Monitoring, Pharmacokinetic and Stability Studies of First-Line Antituberculosis Drugs in Urine

Tuberculosis (TB) remains one of the leading global causes of mortality. Several methods have been established to detect anti-TB agents in human plasma and serum. However, there is a notable absence of studies analyzing TB drugs in urine. Thus, our objective was to validate a method for quantifying first-line anti-TB agents: isoniazid (INH), pyrazinamide (PZA), ethambutol (ETH), and rifampicin (RIF), along with its metabolite 25-desacetylrifampicin, and degradation products: rifampicin quinone and 3-formyl-rifampicin in 10 µL of urine. Chromatographic separation was achieved using a Kinetex Polar C18 analytical column with gradient elution (5 mM ammonium acetate and acetonitrile with 0.1% formic acid). Mass spectrometry detection was carried out using a triple-quadrupole tandem mass spectrometer operating in positive ion mode. The lower limit of quantification (LLOQ) was 0.5 µg/mL for INH, PZA, ETH, and RIF, and 0.1 µg/mL for RIF's metabolites and degradation products. The method was validated following FDA guidance criteria and successfully applied to the analysis of the studied compounds in urine of TB patients. Additionally, we conducted a stability study of the anti-TB agents under various pH and temperature conditions to mimic the urine collection process in different settings (peripheral clinics or central laboratories).

Isoniazid and rifampicin exposure during treatment in drug-susceptible TB

BACKGROUND: Observational real-world studies on therapeutic drug monitoring (TDM) in relation to pharmacokinetic (PK) target values are lacking. This study aims to describe the PK of rifampicin (RIF) and isoniazid (INH) in a real-world setting of patients with drug-susceptible TB in relation to frequently used threshold values.METHODS: A total of 116 patients with TB using standard doses of RIF and INH and who had TDM as part of clinical care were included. Maximum plasma concentration (Cmax) and 24 h area under the concentration time curve (AUC24) at standard and revised doses were described in relation to the threshold values (Cmax ≥8 mg/L for RIF and ≥3 mg/L for INH).RESULTS: For RIF (100 patients), median Cmax and median AUC24 were respectively 7.9 mg/L (IQR 6.0-11.0) and 35.8 mg*h/L (IQR 27.4-57.3) at the first TDM measurement after a standard dose of 600 mg. For INH (90 patients), median Cmax and median AUC24 were respectively 2.9 mg/L (IQR 1.3-2.5) and 12.5 mg*h/L (IQR 8.7-18.9) at the first TDM after a standard dose 300 mg. Overall, more than 50% of study participants had drug exposure below threshold values at the first TDM.CONCLUSION: Our study shows that the measured Cmax values for both RIF and INH were frequently below the pre-specified targets, emphasising the need for better justification of drug exposure targets. These TDM results highlight the need for validating PK targets of anti-TB drugs associated with clinically relevant outcomes.

Dried Blood Spot Sampling to Assess Rifampicin Exposure and Treatment Outcomes among Native and Non-Native Tuberculosis Patients in Paraguay: An Exploratory Study

The aim of this study was to evaluate the difference in drug exposure of rifampicin in native versus non-native Paraguayan populations using dried blood spots (DBS) samples collected utilizing a limited sampling strategy. This was a prospective pharmacokinetic study that enrolled hospitalized tuberculosis (TB) patients from both native and non-native populations receiving oral rifampicin 10 mg/kg once-daily dosing. Steady-state DBS samples were collected at 2, 4, and 6 h after intake of rifampicin. The area under the time concentration curve 0–24 h (AUC0–24) was calculated using a Bayesian population PK model. Rifampicin AUC0–24 < 38.7 mg*h/L was considered as low. The probability of target attainment (PTA) was calculated using AUC0–24/MIC > 271 as a target and estimated MIC values of 0.125 and 0.25 mg/L. In total, 50 patients were included. Native patients (n = 30) showed comparable drug exposure to the non-natives (n = 20), median AUC0–24 24.7 (17.1–29.5 IQR) and 21.6 (15.0–35.4 IQR) mg*h/L (p = 0.66), respectively. Among total patients, only 16% (n = 8) had a rifampicin AUC0–24 > 38.7 mg*h/L. Furthermore, PTA analysis showed that only 12 (24%) of the patients met a target AUC0–24 /MIC ≥ 271, assuming an MIC of 0.125 mg/L, which plummeted to 0% at a wild-type MIC of 0.25 mg/L. We successfully used DBS and limited sampling for the AUC0–24 estimation of rifampicin. Currently, our group, the EUSAT-RCS consortium, is preparing a prospective multinational, multicenter phase IIb clinical trial evaluating the safety and efficacy of high-dose rifampicin (35 mg/kg) in adult subjects using the DBS technique for AUC0–24 estimation.