Systematic Review of Salivary Versus Blood Concentrations of Antituberculosis Drugs and Their Potential for Salivary Therapeutic Drug Monitoring

Model-informed precision dosing: State of the art and future perspectives

Model-informed precision dosing (MIPD) stands as a significant development in personalized medicine to tailor drug dosing to individual patient characteristics. MIPD moves beyond traditional therapeutic drug monitoring (TDM) by integrating mathematical predictions of dosing, and considering patient-specific factors (patient characteristics, drug measurements) as well as different sources of variability. For this purpose, rigorous model qualification is required for the application of MIPD in patients. This review delves into new methods in model selection and validation, also highlighting the role of machine learning in improving MIPD, the utilization of biosensors for real-time monitoring, as well as the potential of models integrating biomarkers for efficacy or toxicity for precision dosing. The clinical evidence of TDM and MIPD is discussed for various medical fields including infection medicine, oncology, transplant medicine, and inflammatory bowel diseases, thereby underscoring the role of pharmacokinetics/pharmacodynamics and specific biomarkers. Further research, particularly randomized clinical trials, is warranted to corroborate the value of MIPD in enhancing patient outcomes and advancing personalized medicine.

Salivary Therapeutic Drug Monitoring of Antimicrobial Therapy: Feasible or Futile?

Personalised drug dosing through therapeutic drug monitoring (TDM) is important to maximise efficacy and to minimise toxicity. Hurdles preventing broad implementation of TDM in routine care include the need of sophisticated equipment and highly trained staff, high costs and lack of timely results. Salivary TDM is a non-invasive, patient-friendly alternative to blood sampling, which has the potential to overcome barriers with traditional TDM. A mobile UV spectrophotometer may provide a simple solution for analysing drug concentrations in saliva samples. Salivary TDM utilising point-of-care tests can support personalised dosing in various settings including low-resource as well as remote settings. In this opinion paper, we describe how hurdles of implementing traditional TDM may be mitigated by salivary TDM with new strategies for patient-friendly point-of-care testing.

Wireless, noninvasive therapeutic drug monitoring system for saliva measurement toward medication management of schizophrenia

As an efficient patient management tool of precision medicine, decentralized therapeutic drug monitoring (TDM) provides new vision for therapy adherence and health management of schizophrenia in a convenient manner. To dispense with psychologically burdensome blood sampling and to achieve real-time, noninvasive, and continual circulating tracking of drugs with narrow therapeutic window, we study the temporal metabolism of clozapine, an antipsychotic with severe side effect, in rat saliva by a wireless, integrated and patient-friendly smart lollipop sensing system. Highly sensitive and efficient sensing performance with acceptable anti-biofouling property was realized based on the synergistic effect of electrodeposited reduced graphene oxide and ionic liquids in pretreatment-free saliva with low detection limit and good accuracy cross-validated with conventional method. On this basis, continual salivary drug levels with distinctive pharmacokinetics were found in different routes of drug administration. Pilot experiment reveals a strong correlation between blood and saliva clozapine and a positive relationship between drug dosage and salivary drug level, indicating potential applications presented by noninvasive saliva analysis towards patient-centered and personalized pharmacotherapy and adherence management via proposed smart lollipop system.

Alternative Methods for Therapeutic Drug Monitoring and Dose Adjustment of Tuberculosis Treatment in Clinical Settings: A Systematic Review

BACKGROUND AND OBJECTIVE

Quantifying exposure to drugs for personalized dose adjustment is of critical importance in patients with tuberculosis who may be at risk of treatment failure or toxicity due to individual variability in pharmacokinetics. Traditionally, serum or plasma samples have been used for drug monitoring, which only poses collection and logistical challenges in high-tuberculosis burden/low-resourced areas. Less invasive and lower cost tests using alternative biomatrices other than serum or plasma may improve the feasibility of therapeutic drug monitoring.

METHODS

A systematic review was conducted to include studies reporting anti-tuberculosis drug concentration measurements in dried blood spots, urine, saliva, and hair. Reports were screened to include study design, population, analytical methods, relevant pharmacokinetic parameters, and risk of bias.

RESULTS

A total of 75 reports encompassing all four biomatrices were included. Dried blood spots reduced the sample volume requirement and cut shipping costs whereas simpler laboratory methods to test the presence of drug in urine can allow point-of-care testing in high-burden settings. Minimal pre-processing requirements with saliva samples may further increase acceptability for laboratory staff. Multi-analyte panels have been tested in hair with the capacity to test a wide range of drugs and some of their metabolites.

CONCLUSIONS

Reported data were mostly from small-scale studies and alternative biomatrices need to be qualified in large and diverse populations for the demonstration of feasibility in operational settings. High-quality interventional studies will improve the uptake of alternative biomatrices in guidelines and accelerate implementation in programmatic tuberculosis treatment.

A randomized, open-label trial of combined nitazoxanide and atazanavir/ritonavir for mild to moderate COVID-19

Background

The nitazoxanide plus atazanavir/ritonavir for COVID-19 (NACOVID) trial investigated the efficacy and safety of repurposed nitazoxanide combined with atazanavir/ritonavir for COVID-19.

Methods

This is a pilot, randomized, open-label multicenter trial conducted in Nigeria. Mild to moderate COVID-19 patients were randomly assigned to receive standard of care (SoC) or SoC plus a 14-day course of nitazoxanide (1,000 mg b.i.d.) and atazanavir/ritonavir (300/100 mg od) and followed through day 28. Study endpoints included time to clinical improvement, SARS-CoV-2 viral load change, and time to complete symptom resolution. Safety and pharmacokinetics were also evaluated (ClinicalTrials.gov ID: NCT04459286).

Results

There was no difference in time to clinical improvement between the SoC (n = 26) and SoC plus intervention arms (n = 31; Cox proportional hazards regression analysis adjusted hazard ratio, aHR = 0.898, 95% CI: 0.492-1.638, p = 0.725). No difference was observed in the pattern of saliva SARS-CoV-2 viral load changes from days 2-28 in the 35% of patients with detectable virus at baseline (20/57) (aHR = 0.948, 95% CI: 0.341-2.636, p = 0.919). There was no significant difference in time to complete symptom resolution (aHR = 0.535, 95% CI: 0.251-1.140, p = 0.105). Atazanavir/ritonavir increased tizoxanide plasma exposure by 68% and median trough plasma concentration was 1,546 ng/ml (95% CI: 797-2,557), above its putative EC90 in 54% of patients. Tizoxanide was undetectable in saliva.

Conclusion

Nitazoxanide co-administered with atazanavir/ritonavir was safe but not better than standard of care in treating COVID-19. These findings should be interpreted in the context of incomplete enrollment (64%) and the limited number of patients with detectable SARS-CoV-2 in saliva at baseline in this trial.

Clinical trial registration

[https://clinicaltrials.gov/ct2/show/NCT04459286], identifier [NCT04459286].

Saliva as Blood Alternative in Therapeutic Monitoring of Teriflunomide-Development and Validation of the Novel Analytical Method

Therapeutic drug monitoring (TDM) is extremely helpful in individualizing dosage regimen of drugs with narrow therapeutic ranges. It may also be beneficial in the case of drugs characterized by serious side effects and marked interpatient pharmacokinetic variability observed with leflunomide and its biologically active metabolite, teriflunomide. One of the most popular matrices used for TDM is blood. A more readily accessible body fluid is saliva, which can be collected in a much safer way comparing to blood. This makes it especially advantageous alternative to blood during life-threatening SARS-CoV-2 pandemic. However, drug’s saliva concentration is not always a good representation of its blood concentration. The aim of this study was to verify whether saliva can be used in TDM of teriflunomide. We also developed and validated the first reliable and robust LC-MS/MS method for quantification of teriflunomide in saliva. Additionally, the effect of salivary flow and swab absorptive material from the collector device on teriflunomide concentration in saliva was evaluated. Good linear correlation was obtained between the concentration of teriflunomide in plasma and resting saliva (p < 0.000016, r = 0.88), and even better between plasma and the stimulated saliva concentrations (p < 0.000001, r = 0.95) confirming the effectiveness of this non-invasive method of teriflunomide’s TDM. The analyzed validation criteria were fulfilled. No significant influence of salivary flow (p = 0.198) or type of swab in the Salivette device on saliva’s teriflunomide concentration was detected. However, to reduce variability the use of stimulated saliva and synthetic swabs is advised.

Everolimus Concentration in Saliva to Predict Stomatitis: A Feasibility Study in Patients with Cancer

BACKGROUND

Most patients with cancer treated with everolimus experience stomatitis, which seriously affects the quality of life. The salivary concentrations of everolimus may predict the incidence and severity of stomatitis. The authors aimed to examine whether it was feasible to quantify the everolimus concentration in saliva and subsequently use it to predict stomatitis.

METHODS

Saliva and whole blood samples were taken from patients with cancer, who were treated with everolimus in the dosage of either 10 mg once a day or 5 mg twice a day. Everolimus concentrations in saliva samples were measured by liquid chromatography-tandem mass spectrometry. A published population pharmacokinetic model was extended with the everolimus concentration in saliva to assess any association between everolimus in the blood and saliva. Subsequently, the association between the occurrence of stomatitis and the everolimus concentration in saliva was studied.

RESULTS

Eleven patients were included in this study; saliva samples were available from 10 patients, including 3 patients with low-grade stomatitis. Everolimus concentrations were more than 100-fold lower in saliva than in whole blood (accumulation ratio 0.00801 and relative standard error 32.5%). Interindividual variability (67.7%) and residual unexplained variability (84.0%) were high. The salivary concentration of everolimus tended to be higher in patients with stomatitis, 1 hour postdose ( P = 0.14).

CONCLUSIONS

Quantification of the everolimus concentration in saliva was feasible and revealed a nonsignificant correlation between everolimus concentration in the saliva and the occurrence of stomatitis. If future research proves this relationship to be significant, the everolimus concentration in the saliva may be used as an early predictor of stomatitis without invasive sampling. Thereby, in patients with high salivary everolimus concentrations, precautions can be taken to decrease the incidence and severity of stomatitis.

Assessing physical and chemical properties of saliva among tuberculosis patients on anti-tuberculosis treatment - An observational study

Background

Tuberculosis (TB) is one of the major systemic conditions which is a preventable and curable infection but remains a significant cause of death. The WHO, in its global plan to stop TB reports, that poor treatment has resulted in the evolution of Mycobacterium tuberculosis strains that do not respond to treatment with the standard first-line combination of anti- tuberculosis medicines, resulting in the emergence of multidrug-resistant tuberculosis in almost every country of the world.The present study was aimed to assess the physical and chemical property of stimulated and unstimulated saliva and identify if any association exist with alterations in taste perception in patients with antituberculosis medications.

Methods

A total of 30 patients on anti-tuberculosis drugs were considered as cases and 30 healthy volunteers were considered as controls and included in the study. All study subjects were assessed for their physical property like flow rate, viscosity, pH and chemical property like sodium, potassium, calcium, phosphorous of stimulated and unstimulated saliva. All the subjects on Anti-tuberculosis drugs were assessed for change in taste perceptions using the standard questionnaire.

Results

There is a significant decrease in the flow rate (0.34 ± 0.06) and pH (5.89 ± 0.37) of unstimulated saliva of patients and the flow rate (0.38 ± 0.07) and viscosity (1.34 ± 0.28) of stimulated saliva among the case group compare to the control group. All the electrolytes' concentrations such as sodium, potassium, calcium, and phosphorous values were significantly altered in stimulated and unstimulated saliva of the case group compared to the control group in which p-value < 0.05 was considered.

Conclusion

There are significant changes in physical and chemical properties of both stimulated and unstimulated saliva which has an effect on taste perception inpatient with anti-tuberculosis medications. Hence, salivary flow rate, pH, viscosity, and salivary electrolytes of tuberculosis patients should be considered as important parameters in guiding the diet, so that there will be an improvement in their taste perception and medication protocol, thus maintaining their nutritional status which leads to improving their health.

Simple simultaneous determination of moxifloxacin and metronidazole in complex biological matrices

A simple, sensitive and rapid RP-HPLC method is presented, for the first time, for the simultaneous determination of moxifloxacin hydrochloride and metronidazole in different biological fluids including saliva and plasma without any matrix interference. The separation was performed using ACN and phosphate buffer (30 : 70% v/v) as the mobile phase on a Zorbax Eclipse Plus-C18 column attached to a guard column. The method was validated according to the FDA guidelines for bioanalytical method validation and was successfully applied for simultaneous determination of the studied drugs in saliva and plasma samples. The good precision and selectivity of the developed method allow it to be used for routine therapeutic drug monitoring of such drugs and it presents a simple and sensitive analytical tool for performing versatile pharmacokinetics and bioavailability studies. A DAD detector is valuable to determine each drug at its maximum wavelength to ensure high sensitivity. Determination of such a combination in saliva introduces a quick and non-invasive alternative to blood analysis.

Semi-Automated Therapeutic Drug Monitoring as a Pillar toward Personalized Medicine for Tuberculosis Management

Standard tuberculosis (TB) management has failed to control the growing number of drug-resistant TB cases worldwide. Therefore, innovative approaches are required to eradicate TB. Model-informed precision dosing and therapeutic drug monitoring (TDM) have become promising tools for adjusting anti-TB drug doses corresponding with individual pharmacokinetic profiles. These are crucial to improving the treatment outcome of the patients, particularly for those with complex comorbidity and a high risk of treatment failure. Despite the actual benefits of TDM at the bedside, conventional TDM encounters several hurdles related to laborious, time-consuming, and costly processes. Herein, we review the current practice of TDM and discuss the main obstacles that impede it from successful clinical implementation. Moreover, we propose a semi-automated TDM approach to further enhance precision medicine for TB management.

Has the Time Come for Systematic Therapeutic Drug Monitoring of First-Line and WHO Group A Antituberculosis Drugs?

ABSTRACT

Tuberculosis (TB) is a major global health issue, with approximately 10 million people being infected each year, and is the leading cause of mortality from infectious disease, with 1.5 million deaths a year. Optimal TB treatment requires a combination of drugs for an adequate treatment duration owing to persistent organisms, hardly accessible infection sites, and a high risk of resistance selection. Long-term therapy increases the risk of patients' loss of adherence, adverse drug reactions, and drug-drug interactions, potentially leading to treatment failure. The high interpatient variability of TB drug exposure is another point eliciting interest in therapeutic drug monitoring (TDM) to optimize treatment. Studies reporting clinically relevant exposure thresholds, which might be proposed as targets toward treatment personalization, are discussed. Practical TDM strategies have also been reported to circumvent issues related to delayed drug absorption and the need for multiple samples when evaluating the area under the curve of drug concentrations. The need for treatment individualization is further emphasized because of the development of multidrug-resistant TB or extensively drug-resistant TB. Finally, the willingness to shorten the treatment duration while maintaining success is also a driver for ensuring adequate exposure to TB drugs with TDM. The aim of the present review was to underline the role of TDM in drug-susceptible TB and World Health Organization group A TB drugs.

Therapeutic Drug Monitoring of Antibiotic Drugs: The Role of the Clinical Laboratory

BACKGROUND

Therapeutic drug monitoring (TDM) of anti-infective drugs is an increasingly complex field, given that in addition to the patient and drug as 2 usual determinants, its success is driven by the pathogen. Pharmacodynamics is related both to the patient (toxicity) and bacterium (efficacy or antibiotic susceptibility). The specifics of TDM of antimicrobial drugs stress the need for multidisciplinary knowledge and expertise, as in any other field. The role and the responsibility of the laboratory in this interplay are both central and multifaceted. This narrative review highlights the role of the clinical laboratory in the TDM process.

METHODS

A literature search was conducted in PubMed and Google Scholar, focusing on the past 5 years (studies published since 2016) to limit redundancy with previously published review articles. Furthermore, the references cited in identified publications of interest were screened for additional relevant studies and articles.

RESULTS

The authors addressed microbiological methods to determine antibiotic susceptibility, immunochemical and chromatographic methods to measure drug concentrations (primarily in blood samples), and endogenous clinical laboratory biomarkers to monitor treatment efficacy and toxicity. The advantages and disadvantages of these methods are critically discussed, along with existing gaps and future perspectives on strategies to provide clinicians with as reliable and useful results as possible.

CONCLUSIONS

Although interest in the field has been the driver for certain progress in analytical technology and quality in recent years, laboratory professionals and commercial providers persistently encounter numerous unresolved challenges. The main tasks that need tackling include broadly and continuously available, easily operated, and cost-effective tests that offer short turnaround times, combined with reliable and easy-to-interpret results. Various fields of research are currently addressing these features.

Therapeutic Drug Monitoring of Anti-infective Drugs: Implementation Strategies for 3 Different Scenarios

BACKGROUND

Therapeutic drug monitoring (TDM) supports personalized treatment. For successful implementation, TDM must have a turnaround time suited to the clinical needs of patients and their health care settings. Here, the authors share their views of how a TDM strategy can be tailored to specific settings and patient groups.

METHODS

The authors selected distinct scenarios for TDM: high-risk, complex, and/or critically ill patient population; outpatients; and settings with limited laboratory resources. In addition to the TDM scenario approach, they explored potential issues with the legal framework governing dose escalation.

RESULTS

The most important issues identified in the different scenarios are that critically ill patients require rapid turnaround time, outpatients require an easy sampling procedure for the sample matrix and sample collection times, settings with limited laboratory resources necessitate setting-specific analytic techniques, and all scenarios warrant a legal framework to capture the use of escalated dosages, ideally with the use of trackable dosing software.

CONCLUSIONS

To benefit patients, TDM strategies need to be tailored to the intended population. Strategies can be adapted for rapid turnaround time for critically ill patients, convenient sampling for outpatients, and feasibility for those in settings with limited laboratory resources.

Comparison of free plasma versus saliva mycophenolic acid exposure following mycophenolate mofetil administration in adult kidney transplant recipients

Therapeutic monitoring (TDM) of mycophenolic acid (MPA) has the potential to improve drug inefficacy and toxicities in kidney transplantation. However, measurement of plasma MPA concentrations is laborious and invasive. This study examined the utility of saliva compared with plasma based TDM of MPA. Paired blood and saliva samples were collected from 47 adult kidney transplant recipients pre- and at 1-, 2-, and 4-hours post mycophenolate mofetil administration. No relationship was observed between saliva MPA concentrations and either total or free plasma MPA concentrations (p > 0.05). This suggests that saliva is a poor direct marker of plasma MPA concentrations and therefore should not be used for MPA TDM.

A mobile microvolume UV/visible light spectrophotometer for the measurement of levofloxacin in saliva

INTRODUCTION

Therapeutic drug monitoring (TDM) for personalized dosing of fluoroquinolones has been recommended to optimize efficacy and reduce acquired drug resistance in the treatment of MDR TB. Therefore, the aim of this study was to develop a simple, low-cost, robust assay for TDM using mobile UV/visible light (UV/VIS) spectrophotometry to quantify levofloxacin in human saliva at the point of care for TB endemic settings.

METHODS

All experiments were performed on a mobile UV/VIS spectrophotometer. The levofloxacin concentration was quantified by using the amplitude of the second-order spectrum between 300 and 400 nm of seven calibrators. The concentration of spiked samples was calculated from the spectrum amplitude using linear regression. The method was validated for selectivity, specificity, linearity, accuracy and precision. Drugs frequently co-administered were tested for interference.

RESULTS

The calibration curve was linear over a range of 2.5-50.0 mg/L for levofloxacin, with a correlation coefficient of 0.997. Calculated accuracy ranged from -5.2% to 2.4%. Overall precision ranged from 2.1% to 16.1%. Application of the Savitsky-Golay method reduced the effect of interferents on the quantitation of levofloxacin. Although rifampicin and pyrazinamide showed analytical interference at the lower limit of quantitation of levofloxacin concentrations, this interference had no implication on decisions regarding the levofloxacin dose.

CONCLUSIONS

A simple UV/VIS spectrophotometric method to quantify levofloxacin in saliva using a mobile nanophotometer has been validated. This method can be evaluated in programmatic settings to identify patients with low levofloxacin drug exposure to trigger personalized dose adjustment.

Levofloxacin pharmacokinetics in saliva as measured by a mobile microvolume UV spectrophotometer among people treated for rifampicin-resistant TB in Tanzania

BACKGROUND

Early detection and correction of low fluoroquinolone exposure may improve treatment of MDR-TB.

OBJECTIVES

To explore a recently developed portable, battery-powered, UV spectrophotometer for measuring levofloxacin in saliva of people treated for MDR-TB.

METHODS

Patients treated with levofloxacin as part of a regimen for MDR-TB in Northern Tanzania had serum and saliva collected concurrently at 1 and 4 h after 2 weeks of observed levofloxacin administration. Saliva levofloxacin concentrations were quantified in the field via spectrophotometry, while serum was analysed at a regional laboratory using HPLC. A Bayesian population pharmacokinetics model was used to estimate the area under the concentration-time curve (AUC0-24). Subtarget exposures of levofloxacin were defined by serum AUC0-24 <80 mg·h/L. The study was registered at Clinicaltrials.gov with clinical trial identifier NCT04124055.

RESULTS

Among 45 patients, 11 (25.6%) were women and 16 (37.2%) were living with HIV. Median AUC0-24 in serum was 140 (IQR = 102.4-179.09) mg·h/L and median AUC0-24 in saliva was 97.10 (IQR = 74.80-121.10) mg·h/L. A positive linear correlation was observed with serum and saliva AUC0-24, and a receiver operating characteristic curve constructed to detect serum AUC0-24 below 80 mg·h/L demonstrated excellent prediction [AUC 0.80 (95% CI = 0.62-0.94)]. Utilizing a saliva AUC0-24 cut-off of 91.6 mg·h/L, the assay was 88.9% sensitive and 69.4% specific in detecting subtarget serum AUC0-24 values, including identifying eight of nine patients below target.

CONCLUSIONS

Portable UV spectrophotometry as a point-of-care screen for subtarget levofloxacin exposure was feasible. Use for triage to other investigation or personalized dosing strategy should be tested in a randomized study.

Pharmacogenetic and Pharmacokinetic Assays from Saliva Samples Can Guarantee Personalized Drug Prescription

Saliva is widely used for clinical and laboratory analysis. This study proposed to use DNA extracted from saliva for genotyping and pharmacokinetics of piroxicam. A fast and efficient genotyping method was used to determine relevant allelic variants of CYP2C9 (*2 and *3), since genetic factors can influence in non-steroidal anti-inflammatory drugs (NSAIDs) metabolization. DNA Extract All Reagents Kit® was used for DNA extraction and genotyping was performed using TaqMan® GTXpress™ Master Mix, SNP genotyping assays and a Viia7 Real-Time PCR system. Volunteers performed sequential collections of saliva samples before and after taking a single dose of piroxicam (0.25 to 72 h) which were used for pharmacokinetics assays. Piroxicam concentrations were analyzed using LC-MS/MS. Sixty-six percent of volunteers were ancestral homozygous (CYP2C9*1/*1), and 34% showed one or both polymorphisms. Of these 34%, 22 individuals showed CYP2C9*2 polymorphism, 8 CYP2C9*3, and 4 CYP2C9*2/*3. Piroxicam pharmacokinetics were performed in 5 subjects. Areas under the curve (AUC0-t(h*ng/mL)) for CYP2C9*1/*1, *1/*2 and *1/*3 were, respectively, 194.33±70.93, 166 and 303. Maximum concentrations (Cmax(ng/mL)) for these genotypes were respectively 6.46±2.56, 4.3 and 10.2. Saliva sampling was a very effective matrix for both pharmacogenetic and pharmacokinetic tests, ensuring the speed of the procedure and the well-being and agreement of the participants. Once having the knowledge about the slow and fast metabolizers, it is possible to make an adequate prescription in order to avoid the adverse effects of the medication and to guarantee greater analgesic comfort to the patients respectively.

From Therapeutic Drug Monitoring to Model-Informed Precision Dosing for Antibiotics

Therapeutic drug monitoring (TDM) and model-informed precision dosing (MIPD) have evolved as important tools to inform rational dosing of antibiotics in individual patients with infections. In particular, critically ill patients display altered, highly variable pharmacokinetics and often suffer from infections caused by less susceptible bacteria. Consequently, TDM has been used to individualize dosing in this patient group for many years. More recently, there has been increasing research on the use of MIPD software to streamline the TDM process, which can increase the flexibility and precision of dose individualization but also requires adequate model validation and re-evaluation of existing workflows. In parallel, new minimally invasive and noninvasive technologies such as microneedle-based sensors are being developed, which-together with MIPD software-have the potential to revolutionize how patients are dosed with antibiotics. Nonetheless, carefully designed clinical trials to evaluate the benefit of TDM and MIPD approaches are still sparse, but are critically needed to justify the implementation of TDM and MIPD in clinical practice. The present review summarizes the clinical pharmacology of antibiotics, conventional TDM and MIPD approaches, and evidence of the value of TDM/MIPD for aminoglycosides, beta-lactams, glycopeptides, and linezolid, for which precision dosing approaches have been recommended.

Integrating Pharmacokinetics and Pharmacodynamics in Operational Research to End Tuberculosis

Tuberculosis (TB) elimination requires innovative approaches. The new Global Tuberculosis Network (GTN) aims to conduct research on key unmet therapeutic and diagnostic needs in the field of TB elimination using multidisciplinary, multisectorial approaches. The TB Pharmacology section within the new GTN aims to detect and study the current knowledge gaps, test potential solutions using human pharmacokinetics informed through preclinical infection systems, and return those findings to the bedside. Moreover, this approach would allow prospective identification and validation of optimal shorter therapeutic durations with new regimens. Optimized treatment using available and repurposed drugs may have an increased impact when prioritizing a person-centered approach and acknowledge the importance of age, gender, comorbidities, and both social and programmatic environments. In this viewpoint article, we present an in-depth discussion on how TB pharmacology and the related strategies will contribute to TB elimination.

A study of the pharmacokinetics of moxifloxacin by the dynamics of its distribution in the blood plasma and saliva of healthy volunteers: a comparative analysis and possible extrapolation methods

Objectives The pharmacokinetics of moxifloxacin in plasma and saliva was investigated in this study. Methods The pharmacokinetics of two specialty drugs of moxifloxacin - reference (Ref) and test (Test) preparation - was studied in 18 healthy volunteers after a single oral dose of 400 mg. Results It was found that the concentration of moxifloxacin in saliva 3-24 h after taking the drugs was statistically significantly higher than that in plasma. A high correlation was observed between the concentration of moxifloxacin in plasma and saliva of volunteers after taking of Ref and Test. Some pharmacokinetic parameters, calculated by the concentration of moxifloxacin in saliva and plasma, are statistically different. A technique is proposed for extrapolating the concentration of moxifloxacin in plasma according to its concentration in saliva using the established linear relationship between the moxifloxacin in plasma and saliva of volunteers in time interval of 3-24 h after taking Ref. Based on the obtained extrapolated concentration of moxifloxacin, the pharmacokinetic parameters were calculated for two studied drugs and did not statistically differ from the parameters calculated according to the data in plasma. Conclusions The developed method of concentration extrapolation allows the use of saliva for pharmacokinetic studies of the tablet preparations of moxifloxacin.

A study of the pharmacokinetics of moxifloxacin by the dynamics of its distribution in the blood plasma and saliva of healthy volunteers: a comparative analysis and possible extrapolation methods

OBJECTIVES

The pharmacokinetics of moxifloxacin in plasma and saliva was investigated in this study.

METHODS

The pharmacokinetics of two specialty drugs of moxifloxacin - reference (Ref) and test (Test) preparation - was studied in 18 healthy volunteers after a single oral dose of 400 mg.

RESULTS

It was found that the concentration of moxifloxacin in saliva 3-24 h after taking the drugs was statistically significantly higher than that in plasma. A high correlation was observed between the concentration of moxifloxacin in plasma and saliva of volunteers after taking of Ref and Test. Some pharmacokinetic parameters, calculated by the concentration of moxifloxacin in saliva and plasma, are statistically different. A technique is proposed for extrapolating the concentration of moxifloxacin in plasma according to its concentration in saliva using the established linear relationship between the moxifloxacin in plasma and saliva of volunteers in time interval of 3-24 h after taking Ref. Based on the obtained extrapolated concentration of moxifloxacin, the pharmacokinetic parameters were calculated for two studied drugs and did not statistically differ from the parameters calculated according to the data in plasma.

CONCLUSIONS

The developed method of concentration extrapolation allows the use of saliva for pharmacokinetic studies of the tablet preparations of moxifloxacin.

Advantages and Challenges of Tailored Regimens for Drug-Resistant Tuberculosis: A StopTB Italia Look into the Future

The emerge of drug-resistant tuberculosis (TB) strain in recent decades is hampering the efforts of the international community to eliminate the disease worldwide. The World Health Organization (WHO) has drafted many strategies to achieve this ambitious goal. In the very beginning, the aim was to standardize inadequate regimens used in many countries and, thereafter, evolved to tackle the social determinants which hinder TB elimination. However, following the path of narrowing the clinical vision to deal with TB, there is an increased need to personalize the treatment considering both patients and pathogen unique characteristics. In our narrative review, we report the advantages and the backwards in developing a method to implement the concept of precision medicine to the treatment of TB. In this dissertation, we highlight the importance to address different aspects of the diseases encompassing the host and pathogen features, as well as the needs to further implement an adequate follow-up based on the available resources. Nevertheless, many things may hamper the vision of precision medicine in TB, such as the complexity and the costs to develop novel compounds and the costs related to global-scale implementation of patient-centered follow-up. To achieve the ambitious goal of TB elimination, a radical change in TB treatment is needed in order to give a more comprehensive approach based both on patients’ peculiarities and driven by drug susceptibility tests and whole-genome sequencing.

PK/PD modeling of 5-hydroxytryptophan (5-HTP) challenge test with cortisol measurement in serum and saliva

This research was planned to build a Pharmacokinetic/Pharmacodynamic (PK/PD) model of 5‐hydroxytryptophan (5‐HTP) challenge study including a circadian rhythm component of cortisol and to predict serum cortisol based on saliva cortisol. Data from three 5‐HTP challenge studies in healthy volunteers were collected. Serum 5‐HTP, saliva, and serum cortisol were sampled as PK and PD marker. The population PK/PD modeling approach was applied. A baseline model of serum cortisol was built to assess the circadian rhythm before a pharmacodynamic model was used to evaluate the drug effect of the 5‐HTP on cortisol. Finally, linear and power function relationships were tested to predict serum cortisol based on saliva cortisol. The PK of 5‐HTP could be described using a one‐compartment model with a transit compartment. The typical value for clearance was 20.40 L h⁻¹ and showed inter‐study variability. A cosine function was chosen and properly described the circadian rhythm of serum cortisol. A linear approximation model was applied to fit the 5‐HTP PD effect on cortisol data with a slope of 4.16 ng mL⁻¹ h. A power function provided a better description than a linear function to relate the saliva and serum cortisol. In conclusion, a circadian rhythm component was built in the PK/PD model of the 5‐HTP challenge test which could better improve the understanding of the stimulating effect on HPA with cortisol change. After the 5‐HTP challenge, saliva cortisol correlated well with serum cortisol and was predictable by a population PK‐PD model.

Evaluation of Saliva as a Potential Alternative Sampling Matrix for Therapeutic Drug Monitoring of Levofloxacin in Patients with Multidrug-Resistant Tuberculosis

Saliva may be a useful alternative matrix for monitoring levofloxacin concentrations in multidrug-resistant tuberculosis (MDR-TB) patients. The objectives of this study were (i) to evaluate the correlation between plasma and salivary levofloxacin (Lfx) concentrations in MDR-TB patients and (ii) to gauge the possibility of using saliva as an alternative sampling matrix for therapeutic drug monitoring of Lfx in areas where TB is endemic. This was a prospective pharmacokinetic study that enrolled MDR-TB patients receiving levofloxacin (750- to 1,000-mg once-daily dosing) under standardized treatment regimen in Nepal. Paired blood and saliva samples were collected at steady state. Lfx concentrations were quantified using liquid chromatography-tandem mass spectrometry. Pharmacokinetic parameters were calculated using noncompartmental kinetics. Lfx drug exposures were evaluated in 23 MDR-TB patients. During the first month, the median (interquartile range [IQR]) areas under the concentration-time curve from 0 to 24 h (AUC_0-24) were 67.09 (53.93 to 98.37) mg ⋅ h/liter in saliva and 99.91 (76.80 to 129.70) mg ⋅ h/liter in plasma, and the saliva plasma (S/P) ratio was 0.69 (0.53 to 0.99). Similarly, during the second month, the median (IQR) AUC_0-24 were 75.63 (61.45 to 125.5) mg ⋅ h/liter in saliva and 102.7 (84.46 to 131.9) mg ⋅ h/liter in plasma, with an S/P ratio of 0.73 (0.66 to 1.18). Furthermore, large inter- and intraindividual variabilities in Lfx concentrations were observed. This study could not demonstrate a strong correlation between plasma and saliva Lfx levels. Despite a good Lfx penetration in saliva, the variability in individual saliva-to-plasma ratios limits the use of saliva as a valid substitute for plasma. Nevertheless, saliva could be useful in semiquantitatively predicting Lfx plasma levels. (This study has been registered at ClinicalTrials.gov under identifier NCT03000517.).