Therapeutic drug monitoring of antimicrobials

Osteoarticular Mycoses

Osteoarticular mycoses are chronic debilitating infections that require extended courses of antifungal therapy and may warrant expert surgical intervention. As there has been no comprehensive review of these diseases, the International Consortium for Osteoarticular Mycoses prepared a definitive treatise for this important class of infections. Among the etiologies of osteoarticular mycoses are Candida spp., Aspergillus spp., Mucorales, dematiaceous fungi, non-Aspergillus hyaline molds, and endemic mycoses, including those caused by Histoplasma capsulatum, Blastomyces dermatitidis, and Coccidioides species. This review analyzes the history, epidemiology, pathogenesis, clinical manifestations, diagnostic approaches, inflammatory biomarkers, diagnostic imaging modalities, treatments, and outcomes of osteomyelitis and septic arthritis caused by these organisms. Candida osteomyelitis and Candida arthritis are associated with greater events of hematogenous dissemination than those of most other osteoarticular mycoses. Traumatic inoculation is more commonly associated with osteoarticular mycoses caused by Aspergillus and non-Aspergillus molds. Synovial fluid cultures are highly sensitive in the detection of Candida and Aspergillus arthritis. Relapsed infection, particularly in Candida arthritis, may develop in relation to an inadequate duration of therapy. Overall mortality reflects survival from disseminated infection and underlying host factors.

Antifungal Drugs TDM: Trends and Update

PURPOSE

The increasing burden of invasive fungal infections results in growing challenges to antifungal (AF) therapeutic drug monitoring (TDM). This review aims to provide an overview of recent advances in AF TDM.

METHODS

We conducted a PubMed search for articles during 2016-2020 using "TDM" or "pharmacokinetics" or "drug-drug-interaction" with "antifungal," consolidated for each AF. Selection was limited to English language articles with human data on drug exposure.

RESULTS

More than 1000 articles matched the search terms. We selected 566 publications. The latest findings tend to confirm previous observations in real-life clinical settings. The pharmacokinetic variability related to special populations is not specific but must be considered. AF benefit-to-risk ratio, drug-drug interaction (DDI) profiles, and minimal inhibitory concentrations for pathogens must be known to manage at-risk situations and patients. Itraconazole has replaced ketoconazole in healthy volunteers DDI studies. Physiologically based pharmacokinetic modeling is widely used to assess metabolic azole DDI. AF prophylactic use was studied more for Aspergillus spp. and Mucorales in oncohematology and solid organ transplantation than for Candida (already studied). Emergence of central nervous system infection and severe infections in immunocompetent individuals both merit special attention. TDM is more challenging for azoles than amphotericin B and echinocandins. Fewer TDM requirements exist for fluconazole and isavuconazole (ISZ); however, ISZ is frequently used in clinical situations in which TDM is recommended. Voriconazole remains the most challenging of the AF, with toxicity limiting high-dose treatments. Moreover, alternative treatments (posaconazole tablets, ISZ) are now available.

CONCLUSIONS

TDM seems to be crucial for curative and/or long-term maintenance treatment in highly variable patients. TDM poses fewer cost issues than the drugs themselves or subsequent treatment issues. The integration of clinical pharmacology into multidisciplinary management is now increasingly seen as a part of patient care.

Therapeutic drug monitoring of amikacin: quantification in plasma by liquid chromatography-tandem mass spectrometry and work experience of clinical pharmacists

Objectives

As part of the service provided by clinical pharmacists in our hospital, an assay for plasma amikacin quantification by liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been established for clinical use since 2018. This study was undertaken to describe: (1) the establishment of this assay; (2) the application and results of the testing; and (3) the analysis and impact for patients.

Methods

The amikacin quantification assay was validated and the plasma amikacin concentration data were extracted and analysed. The clinical data for related patients were collected from electronic health and medical records.

Results

121 plasma samples from 53 patients were included in this statistical analysis. The use of amikacin was mostly monitored in the intensive care unit and the haematology department, and the monitoring range of amikacin concentrations were about 0.1–57µg/mL. The main indications for amikacin concentration detection were combined medications, impaired renal function, or people over 65 years old, which may increase the incidence of adverse reactions. Amikacin prescribing decisions were diversified due to the combination of assay results and clinical disease progression, and the effective rate of amikacin administration was about 52.8% (28/53).

Conclusions

The assay for plasma amikacin concentration has been successfully established to monitor the clinical use of amikacin, and the assay results served as one of the references for amikacin prescribing decisions.

Past, present and future perspectives of therapeutic drug monitoring in India

Therapeutic drug monitoring (TDM) is the clinical practice of performing drug assays and interpreting results to maintain constant therapeutic concentrations in patients' bloodstream. Conventional TDM was started way back in the 1960s and served to optimise pharmacotherapy by maximising therapeutic efficacy by evaluating efficacy failure and monitoring drug compliance, while minimising adverse events, in drugs with a narrow therapeutic range. Currently, the scope of TDM has been extended to additional indications which are of importance to India. Apart from the conventional indications, TDM can also help combat drug resistance amongst patients treated with antimicrobials, including anti-tubercular drugs and critically ill patients with compromised pharmacokinetics. TDM is also indicated for patients on antiretroviral drugs under specific clinical scenarios and is of high importance to India. Target concentration intervention (TCI) and apriori TDM (by merging TDM with pharmacogenomics) are emerging fields explored in developed nations. The authors sought to assess the evolution of TDM in India and evaluate the potential impact of newer indications in rationalising pharmacotherapy. In the mid-1980s, TDM was presented to India. Despite showing some initial progress, its use is limited to conventional indications. Its utility is also challenged by cost and higher reliance on conventional prescribing practices. However, the newer indications such as antimicrobial resistance, tuberculosis and HIV, with their high prevalence in developing nations, present an opportunity for the growth of TDM in these countries. Indian clinician's awareness and buoyant demands alongside expert contributions from clinical pharmacologists could widen its scope.

Simultaneous quantification of plasma levels of 12 antimicrobial agents including carbapenem, anti-methicillin-resistant Staphylococcus aureus agent, quinolone and azole used in intensive care unit using UHPLC-MS/MS method

OBJECTIVES

Critically ill patients in intensive care unit (ICU) are susceptible to infectious diseases, thus empirical therapy is recommended. However, the therapeutic effect in ICU patients is difficult to predict due to fluctuation in pharmacokinetics because of various factors. This problem can be solved by developing personalized medicine through therapeutic drug monitoring. However, when different measurement systems are used for various drugs, measurements are complicated and time consuming in clinical practice. In this study, we aimed to develop an assay using ultra-high performance liquid chromatography coupled with tandem mass spectrometry for simultaneous quantification of 12 antimicrobial agents commonly used in ICU: doripenem, meropenem, linezolid, tedizolid, daptomycin, ciprofloxacin, levofloxacin, pazufloxacin, fluconazole, voriconazole, voriconazole N-oxide which is a major metabolite of voriconazole, and posaconazole.

DESIGN & METHODS

Plasma protein was precipitated by adding acetonitrile and 50% MeOH containing standard and labeled IS. The analytes were separated with an ACQUITY UHPLC CSH C18 column, under a gradient mobile phase consisting of water and acetonitrile containing 0.1% formic acid and 2 mM ammonium formate.

RESULTS

The method fulfilled the criteria of US Food and Drug Administration for assay validation. The recovery rate was more than 84.8%. Matrix effect ranged from 79.1% to 119.3%. All the calibration curves showed good linearity (back calculation of calibrators: relative error ≤ 15%) over wide concentration ranges, which allowed determination of C_max and C_trough. Clinical applicability of the novel method was confirmed.

CONCLUSIONS

We have developed an assay for simultaneous quantification of 12 antimicrobial agents using a small sample volume of 50 μL with a short assay time of 7 min. Our novel method may contribute to simultaneous calculation of pharmacokinetic and pharmacodynamic parameters.

Impact of Therapeutic Drug Monitoring on Once-Daily Regimen of Amikacin in Patients With Urinary Tract Infection: A Prospective Observational Study

BACKGROUND

Amikacin is a semisynthetic antibiotic used in the treatment of gram-negative bacterial infections and has a narrow therapeutic index. Although therapeutic drug monitoring is recommended for amikacin, it is not routinely performed because of the use of a less toxic once-daily regimen. Only few studies have evaluated the role of therapeutic drug monitoring in patients treated with amikacin. The objective of our study was to find an association between the pharmacokinetic parameters of amikacin and the time required for a clinical cure, creatinine clearance, and frequency of ototoxicity in patients with urinary tract infection treated for 7 or more days.

METHODS

A prospective study was conducted on patients with urinary tract infections who were administered amikacin for 7 or more days. Blood samples were obtained from the patients to measure the maximum drug concentration (Cmax) and trough concentration (Ctrough). Minimum inhibitory concentration (MIC) values were determined for patients with positive urine cultures. Serum creatinine levels were estimated every 3 days. The auditory assessment was performed using pure tone audiometry at baseline and weekly until the patients were discharged. Levels of amikacin were analyzed using a validated liquid chromatography-tandem mass spectrometry method.

RESULTS

Of 125 patients analyzed, the median time required for a clinical cure was less in the group of patients who achieved a Cmax/MIC ratio ≥8 than it was in those who did not achieve this level [7 versus 8 days (P = 0.02)]. The Ctrough of amikacin was associated with the change in serum creatinine level (P = 0.01) and the incidence of nephrotoxicity (P = 0.004).

CONCLUSIONS

In patients receiving short-term amikacin therapy, Cmax/MIC value can be used to predict the time required for a clinical cure. Ctrough can be used to predict the occurrence of nephrotoxicity in patients receiving amikacin therapy.

Pinacho D. Personalized Medicine for Antibiotics: The Role of Nanobiosensors in Therapeutic Drug Monitoring

Due to the high bacterial resistance to antibiotics (AB), it has become necessary to adjust the dose aimed at personalized medicine by means of therapeutic drug monitoring (TDM). TDM is a fundamental tool for measuring the concentration of drugs that have a limited or highly toxic dose in different body fluids, such as blood, plasma, serum, and urine, among others. Using different techniques that allow for the pharmacokinetic (PK) and pharmacodynamic (PD) analysis of the drug, TDM can reduce the risks inherent in treatment. Among these techniques, nanotechnology focused on biosensors, which are relevant due to their versatility, sensitivity, specificity, and low cost. They provide results in real time, using an element for biological recognition coupled to a signal transducer. This review describes recent advances in the quantification of AB using biosensors with a focus on TDM as a fundamental aspect of personalized medicine.

Therapeutic drug monitoring in treatment-experienced HIV-infected patients receiving darunavir-based salvage regimens: A case series

Therapeutic drug monitoring (TDM) constitutes a compelling approach for the optimization of antiretroviral therapy in treatment-experienced HIV-1 patients. While various inhibitory indices have been proposed to predict virologic outcome, there is a lack of consensus on the clinical value of TDM. Here, we report the comparative results of TDM in 14 HIV-1-infected patients who had previously received at least two different PI-based regimens and who initiated darunavir (DRV)-based salvage therapy. Pharmacokinetic/pharmacodynamics (PK/PD) parameters were calculated for each subject. Seventy-nine percent of subjects had a viral load <50 copies/mL at 48 weeks. The only subject with two consecutive viral loads >50 copies/mL at the end of the study period was the patient with the lowest instantaneous inhibitory potential (IIP). The sample size was insufficient to show an association between any of the PK/PD parameters and virologic response. Based on our observations, we suggest that the utility of IIP for antiretroviral combinations for the prediction of virologic outcome in HIV-1 drug-experienced patients should be studied further.

Development of a liquid chromatography tandem mass spectrometry method for the simultaneous measurement of voriconazole, posaconazole and itraconazole

Background Azole-based antifungals are the first-line therapy for some of the most common mycoses and are now also being used prophylactically to protect immunocompromised patients. However, due to variability in both their metabolism and bioavailability, therapeutic drug monitoring is essential to avoid toxicity but still gain maximum efficacy. Methods Following protein precipitation of serum with acetonitrile, 20  µL of extract was injected onto a 2.1 × 50 mm Waters Atlantis dC18 3  µm column. Detection was via a Waters Quattro Premier XE tandem mass spectrometer operating in ESI-positive mode. Multiple reaction monitoring (MRM) detected two product ions for each compound and one for each isotopically labelled internal standard. Ion suppression, linearity, stability, matrix effects, recovery, imprecision, lower limits of measuring interval and detection were all assessed. Results Optimal chromatographic separation was achieved using gradient elution over 8 minutes. Voriconazole, posaconazole and itraconazole eluted at 1.71, 2.73 and 3.41 min, respectively. The lower limits of measuring interval for all three compounds was 0.1 mg/L. The assay was linear to 10 mg/L for voriconazole (R²= 0.995) and 5 mg/L for posaconazole (R²= 0.990) and itraconazole (R²= 0.991). The assay was both highly accurate and precise with % bias of voriconazole, posaconazole and itraconazole, respectively, when compared with previous NEQAS samples. The intra-assay precision (CV%) was 1.6%, 2.5% and 1.9% for voriconazole, posaconazole and itraconazole, respectively, across the linear range. Conclusion A simple and robust method has been validated for azole antifungal therapeutic drug monitoring. This new assay will result in a greatly improved sample turnaround time and will therefore vastly increase the clinical utility of azole antifungal drug monitoring.