To Therapeutic Drug Monitoring Research Articles

Evaluating Adherence to Therapeutic Drug Monitoring Guidelines for Gentamicin in Neonatal Care: A Retrospective Study at the Maternity and Children's Hospital in Makkah.

In this study, we assess healthcare providers' adherence to therapeutic drug monitoring (TDM) guidelines for gentamicin in neonates. Conducted at the Maternity and Children's Hospital in Makkah, Saudi Arabia, from July 2020 to July 2022, it retrospectively analyzed the compliance of healthcare workers in managing neonates treated with gentamicin. Covering 410 neonates, primarily diagnosed with respiratory distress (56%) and sepsis (32%), the study revealed that while a majority of trough and peak levels conformed to guidelines, substantial deviations were noted in cases of respiratory distress. This underlines the necessity for targeted TDM strategies, particularly in managing respiratory distress in neonates, to ensure optimal treatment efficacy and safety. The findings urge stringent compliance with TDM guidelines, emphasizing personalized approaches in neonatal gentamicin therapy for improved healthcare outcomes.

Linezolid dose adjustment according to therapeutic drug monitoring helps reach the goal concentration in severe patients, and the oldest seniors benefit more

BackgroundThe elderly with severe infection increased dramatically in intensive care unit (ICU). Proper antimicrobial therapy help improve the prognosis. Linezolid, as an antimicrobial drug, is commonly utilized to treat patients infected with methicillin-resistant S. aureus and vancomycin-resistant enterococci. Clinical evidence suggests elderly patients prone to linezolid overexposure. Here, we describe the results of three years’ linezolid adjustment experiences according to therapeutic drug monitoring (TDM), especially in the oldest old.MethodsLinezolid therapeutic drug monitoring data were collected between January 2020 and November 2022 from patients who were admitted to ICU and treated with linezolid. All the patients started with a dosage of 600 mg, twice daily. The first TMD was carried out ten minutes before the seventh administration. The dosage adjustment was determined by the doctor according to the first TMD and patients' condition, and the repeated TDM was conducted as required. The dosage adjustment in different age group was recorded. Laboratory data were compared between the old and the oldest old. The high mortality risk of the oldest old was also explored.ResultsData of 556 linezolid TDM from 330 patients were collected. Among which, 31.6%, 54.8%, and 75% of patients had supra-therapeutic linezolid trough concentrations at the first TDM assessment in different age group, leading to the dosage adjustment rate of 31.0%, 40.3%, 68.8% respectively. The linezolid dosage adjustments according to TDM help to reach therapeutic concentration. The oldest old was in high risk of linezolid overexposure with lowercreatinine clearance. The norepinephrine maximum dosage but not linezolid Cmin was associated with 28-day mortality in the oldest old.ConclusionsElderly patients with linezolid conventional 600 mg twice-daily dose might be at a high risk of overexposure, especially in the oldest old. The linezolid dosage adjustments according to TDM help reach the therapeutic concentration. The high mortality of the oldest old was not related with initial linezolid overexposure.

B-297 Effortless and Streamlined Workflow for Absolute Quantitation of Therapeutic Monoclonal Antibodies Using Promise Proteomics mAbXmise Kits and TSQ Altis Plus Mass Spectrometer

Abstract Background Laboratories continuously seek improved productivity and efficacy for clinical testing, ultimately impacting the turn-around time and sample throughput. Various efforts have been made including rapid and high-throughput testing, automation, and high-end instrumentation. This also applies to therapeutic drug monitoring (TDM) of therapeutic monoclonal antibodies (mAbs). In particular, mass spectrometry (MS) has gained significant popularity in clinical laboratories for TDM of mAbs due to its great versatility to measure such complex biological proteins qualitatively and quantitatively. Here we present the streamlined workflow for the absolute quantitation of therapeutic mAbs using the Promise Proteomics mAbXmise kits and the Thermo Scientific™ TSQ Altis™ Plus mass spectrometer. The mAbXmise kit is the first commercial ready-to-use kit that offers all the necessary reagents for the LC-MS/MS assay including the stable-isotope labeled (SIL) proteins of the target mAbs (SIL-mAbs). The TSQ Altis™ Plus mass spectrometer is the latest generation of the TSQ MS series, offering superior acquisition speeds, sensitivity, selectivity, and robustness for routine and high-volume targeted protein quantitation. Methods The experimental workflow followed the instructions provided by Promise Proteomics with minor modifications (refer to instructions manual—https://customer.mabxmise.com). The kits used in this study include pre-coated plates with a full-length SIL-mAb corresponding to each target mAb sequence as internal standards with purity >95% and isotopic corporation >98%. Thus, the ITDM1 kit contains 2 SIL-mAbs and the OTDM1 kit contains 7 SIL-mAbs pre-coated in each plate. The kits also provide buffer stocks, reagents, 6 calibration standards including zero, and 2 QC controls. Each kit provides 12 strips capable of 96 sample preparation. The calibrators and QC samples were added to the mAbXmise plate and subjected to immunocapture followed by trypsin digestion. LC-MS/MS was performed using a Thermo Scientific™ Vanquish™ Flex UHPLC system hyphenated to TSQ Altis™ Plus mass spectrometer. Results Highly comparable results were observed across six replicates for both OTDM1 and ITDM1 kits with R2 values >0.99 and % RSD of peak areas of peptides <15. After confirming the complete sample preparation of 96 samples, an evaluation of LC-MS analytical performance was performed. The results show great linearity with R2 > 0.998 over measured calibration concentration points for all the OTDM1 and ITDM1 target peptides, respectively. Also, the data support the reproducible LC-MS measurement of the entire plate providing % RSD <10. The accuracy of QC samples was determined to be between 94 and 103% for OTDM1 peptides with a precision of <7% CV and between 95 and 107 % for ITDM peptides with a precision of <9% CV. The response of CAL1 (LLOQ) was 5 times higher than CAL0 for all the target peptides with accuracy between 96 and 112% and precision of <11% CV. Additionally, extremely reproducible retention times were observed from all SIL-mAb peptides with RT difference ±0.03 min during the evaluation. Conclusion The workflow tested in this report generated sensitive and robust data with high confidence, emphasizing the capability of MS-based TDM of mAbs as routine testing.

Investigating Perampanel Antiepileptic Drug by DFT Calculations and SERS with Custom Spinning Cell.

SERS, a clinical practice where medical doctors can monitor the drug concentration in biological fluids, has been proposed as a viable approach to therapeutic drug monitoring (TDM) of the antiepileptic drug Perampanel. The adoption of an acidic environment during the SERS experiments was found to be effective in enhancing the spectroscopic signal. In this work, we combine SERS experiments, conducted with a custom spinning cell in controlled acidic conditions, with DFT calculations aimed at investigating the possible protonated forms of Perampanel. The DFT-simulated Raman spectra of protonated Perampanel accounts for most of the observed SERS signals, thus explaining the effective role of protonation of the analyte. Our results suggest protonation as a viable approach to fostering SERS of alkaline drugs.

The fluorescence and colorimetric dual-readout probe for clinical rapid detection of mycophenolic acid by the poly(ethylenimine)/silica-coated CdTe quantum dots

It is particularly meaningful to therapeutic drug monitoring (TDM) of mycophenolic acid (MPA) for transplant patients to maximize the drug efficacy and minimize the adverse effect. In this study, a novel fluorescence and colorimetric dual-readout probe was put forward to fast and reliable detect MPA. The blue fluorescence of MPA was largely enhanced in the presence of poly (ethylenimine) (PEI), while the red fluorescence of CdTe@SiO2 (silica-coated CdTe quantum dots) provided a reliable reference signal. Hence, combining PEI70,000 and CdTe@SiO2, a fluorescence and colorimetric dual-readout probe could be constructed. For fluorescence measurement of MPA, the linearity was obtained in the MPA concentration range of 0.5–50 μg/mL, with a limit of detection (LOD) of 33 ng/mL. For the visual detection, the fluorescent colorimetric card was established in the MPA concentration from 0.5 to 50 μg/mL corresponding to the fluorescence color from red to violet and then to blue, which could be used for semi-quantification. Furthermore, in the light of the ColorCollect APP by the smartphone, the ratio of blue and red brightness values was linear with the MPA concentration from 1 to 50 μg/mL; thus, quantification of MPA could be realized by APP with the LOD of 83 ng/mL. The developed method was successfully applied to the analysis of MPA in the plasma samples of three patients after oral administration of mycophenolate mofetil, which was the prodrug of MPA. The result was comparable to those obtained by the clinically widely-used enzyme multiplied immunoassay technique. The developed probe was fast, cost-effective and operational convenience, and possessed high potential for TDM of MPA.

LC-MS/MS Application in Pharmacotoxicological Field: Current State and New Applications.

Nowadays, it is vital to have new, complete, and rapid methods to screen and follow pharmacotoxicological and forensic cases. In this context, an important role is undoubtedly played by liquid chromatography-tandem mass spectrometry (LC-MS/MS) thanks to its advanced features. This instrument configuration can offer comprehensive and complete analysis and is a very potent analytical tool in the hands of analysts for the correct identification and quantification of analytes. The present review paper discusses the applications of LC-MS/MS in pharmacotoxicological cases because it is impossible to ignore the importance of this powerful instrument for the rapid development of pharmacological and forensic advanced research in recent years. On one hand, pharmacology is fundamental for drug monitoring and helping people to find the so-called "personal therapy" or "personalized therapy". On the other hand, toxicological and forensic LC-MS/MS represents the most critical instrument configuration applied to the screening and research of drugs and illicit drugs, giving critical support to law enforcement. Often the two areas are stackable, and for this reason, many methods include analytes attributable to both fields of application. In this manuscript, drugs and illicit drugs were divided in separate sections, with particular attention paid in the first section to therapeutic drug monitoring (TDM) and clinical approaches with a focus on central nervous system (CNS). The second section is focused on the methods developed in recent years for the determination of illicit drugs, often in combination with CNS drugs. All references considered herein cover the last 3 years, except for some specific and peculiar applications for which some more dated but still recent articles have been considered.

A Wearable Aptamer Microneedle Patch for Minimally-Invasive Therapeutic Drug Monitoring

To realize personalized medicine, the right drug needs to be delivered to the right patient at the right dose. However, it is extremely challenging to dose drugs with narrow therapeutic windows (e.g., antibiotics). For these drugs, due to the small difference between ineffective and toxic concentration levels, the prescribed dosage may result in a circulating concentration outside the therapeutic window, leading to toxicity (e.g., kidney injury) and/or ineffective pharmacotherapy. To prevent such adverse events, patients under these medications are committed to therapeutic drug monitoring (TDM), which in the current clinical practice involves repeated and invasive blood draws followed by labor-intensive and high-cost lab-based analyses (e.g., chromatography, immunoassay). The turnaround times for results are prolonged, and thus, inadequate to allow for timely intervention.Wearable pharmaceutical sensing systems—capable of tracking the medication’s concentration in a continuous and non-/minimally-invasive manner—are well-suited to address these challenges encountered in current TDM practice. To establish a generalizable wearable TDM modality for a broad range of pressing clinical applications, we focus on tracking pharmaceuticals in interstitial fluid (ISF). The choice for ISF is motivated by noting that a wide panel of pharmaceuticals, particularly those with stringent personalized dosing requirements, partition into ISF with high correlation to their circulating levels. To target these analytes, microneedles emerged as promising tools, which are capable of overcoming the skin barrier to directly access ISF in a minimally-invasive manner without user intervention. By integrating sensors on microneedle substrates (e.g., on-the-tip electrochemical sensor fabrication), ISF analytes can be monitored continuously. However, currently demonstrated in-situ ISF sensors are mainly based on enzymatic sensing, which significantly limits the scope of target analytes to the ones with enzymes available.Overcoming this limitation, we devised a low-cost affinity-based biosensor-on-needle fabrication scheme, which was utilized to develop an aptamer microneedle patch (AMPatch). Our AMPatch consists of: 1) a microneedle electrode substrate based on repurposed acupuncture gold needles, leveraging the validated skin puncture performance and the high conductivity of these needles; 2) a gold nanoparticle (AuNP) coating, rendering a high-quality gold surface (comparable to standard electrodes used in electrochemistry) for strong and compact aptamer immobilization; and 3) an aptamer/signal reporter self-assembled monolayer, transducing the target binding events into measurable electrical readouts. We specifically target tobramycin, an antibiotic with a narrow therapeutic window and large intra-subject pharmacokinetic variations, which in the current clinical practice requires multiple TDM sessions to achieve an optimal dosing. Leveraging the developed AMPatch, we demonstrated real-time continuous monitoring of tobramycin ex-vivo (in a phantom gel model, mimicking the dermal ISF testing scenario) and in-vivo (via rat studies). Our results demonstrate the suitability of the AMPatch for minimally-invasive monitoring of the target drug’s pharmacokinetic profile and its potential as a viable TDM tool for personalized pharmacotherapy. Acknowledgements: This work was supported by the National Science Foundation (Award 1847729) and the UCLA Innovation Fund.

Risk factors for anti-drug antibody formation to infliximab: Secondary analyses of a randomised controlled trial.

BackgroundAnti‐drug antibodies (ADAb) frequently form early in the treatment course of infliximab and other tumour necrosis factor (TNF) inhibitors, leading to treatment failure and adverse events.ObjectiveTo identify risk factors for ADAb in the early phase of infliximab treatment.MethodsPatients (n = 410) with immune‐mediated inflammatory diseases who initiated infliximab treatment were included in the 38‐week Norwegian Drug Monitoring Trial (NOR‐DRUM) A and randomised 1:1 to therapeutic drug monitoring (TDM) or standard therapy. Serum levels of infliximab and ADAb were measured at each infusion. Possible risk factors for ADAb formation were assessed using logistic regression, adjusting for potential confounders.ResultsADAb were detected in 78 (19%) patients. A diagnosis of rheumatoid arthritis (RA) (odds ratio [OR], 1.9 [95% confidence interval [CI] 1.0–3.6]) and lifetime smoking (OR, 2.0 [CI 1.1–3.6]) were baseline risk factors, while baseline use of concomitant immunosuppressors (OR, 0.4 [CI 0.2–0.8]) and a diagnosis of spondyloarthritis (SpA) (OR, 0.4 [CI 0.2–0.8]) reduced the risk of ADAb. Higher disease activity during follow‐up (OR, 1.1 [CI 1.0–1.1]) and “drug holidays” of more than 11 weeks (OR, 4.1 [CI 1.2–13.8]) increased the risk of ADAb, whereas higher infliximab doses (OR, 0.1 [CI 0.0–0.3) and higher serum infliximab concentrations (OR, 0.7 [CI 0.6–0.8]) reduced the risk of immunogenicity.ConclusionSeveral risk factors for ADAb formation during early‐phase infliximab treatment were identified. This knowledge provides a basis for treatment strategies to mitigate the formation of ADAb and identify patients in whom these measures are of particular importance.

Area-under-the-Curve-Based Mycophenolate Mofetil Dosage May Contribute to Decrease the Incidence of Graft-versus-Host Disease after Allogeneic Hematopoietic Cell Transplantation in Pediatric Patients.

Acute graft-versus-host disease (GvHD) remains the second leading cause of death, after disease relapse, in patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT). The medical records of 112 pediatric patients who underwent allo-HSCT from matched unrelated and haploidentical donors were analyzed. Patients were divided into two groups, according to the GvHD prophylactic regimen used. In the control group, GvHD prophylaxis consisted of cyclosporine A (CsA) and methotrexate (MTX) or CsA and mycophenolate mofetil (MMF) at a standard daily dose of 30 mg/kg. All subjects in the study group received tacrolimus (FK506) and MMF. In this group, MMF was subjected to therapeutic drug monitoring (TDM) through mycophenolic acid (MPA) area under the curve AUC0–12. We found a statistically significant difference in both overall acute GvHD (p < 0.0001) and overall chronic GvHD (p < 0.05) incidence between the study and the control group. The initial daily MMF dose and the age at transplant in the study group proved to be inversely correlated (r = −0.523, p < 0.0001). The children under six years of age required a significantly higher daily MMF dose (p < 0.008). This study showed that pharmacological monitoring of MPA AUC0–12 concentration allowed a reduction in the incidence of acute and chronic GvHD. MMF showed age-dependent pharmacokinetics due to greater drug clearance in younger children.

Copper nanoparticles for SERS-based determination of some cephalosporin antibiotics in spiked human urine

Copper nanoparticles (CuNPs) were prepared through a wet chemistry method to be used as substituents for noble-metal-based materials in the determination of cephalosporin antibiotics in urine using surface-enhanced Raman spectroscopy (SERS). The synthesis of the CuNPs was optimized to maximize the analytical signal, and microwave heating was used to increase the reaction rate and improve the homogeneity of the CuNPs. Ceftriaxone (CTR), cefazolin (CZL), and cefoperazone (CPR) were used as the analytes of interest. The determination tests were performed on artificially spiked samples of real human urine with concentrations corresponding to therapeutic drug monitoring (TDM) (50–500 μg mL−1). Urine samples collected in the morning and during the day were used to account for deviations in the urine composition, and the universality of the proposed protocol was ensured by performing sample dilution as a pretreatment. The use of calibration plots in the form of Freundlich adsorption isotherms yielded linear calibration plots. All limits of detection were lower than the minimal concentrations required for TDM, equaling 7.5 (CTR), 8.8 (CZL), and 36 (CPR) μg mL−1. Comparison of CuNPs with Ag and Au nanoparticles (AgNPs and AuNPs, respectively) confirmed that CuNPs offered a competitively high Raman enhancement efficiency (for excitation at 638 nm). Further, although the CuNPs demonstrated poorer temporal stability as compared with the AgNPs and AuNPs, the use of freshly prepared CuNPs resulted in satisfactory accuracy (recovery = 93–107%). Given the short analysis time (<20 min, including the time for the synthesis of the CuNPs and the SERS measurements using a portable Raman spectrometer), low sensitivity to the presence of the primary intrinsic urine components and satisfactory figures of merit of the proposed protocol for the determination of cephalosporin antibiotics in urine, it should be suitable for use in TDM.

Patient-Led Remote Intracapillary Pharmacokinetic Sampling (Fingerpricks): Validation and Acceptability for Home Therapeutic Drug Monitoring in Patients with Ibd in the COVID-19 Pandemic

Background: During the first wave of the coronavirus (COVID-19) pandemic, restrictive public health measures including prolonged shielding, were recommended by the United Kingdom government for many patients with immune-mediated inflammatory disorders treated with immunosuppressive and biologic drugs. Low-volume intracapillary blood sampling can be undertaken by patients at home and returned by post and may ensure access to therapeutic drug monitoring (TDM) for all patients irrespective of shielding status.Methods: We undertook a cross-sectional blood sampling methods comparison study to assess the clinical validity and acceptability to patients of low volume intracapillary testing for serum TDM enzyme-linked immunosorbent assays (ELISA) compared to conventional venepuncture. Sample types were compared using linear regression and fit-for-purpose equivalence was defined using total allowable error (TEa) rates derived using interassay coefficient of variations from routine clinical practice. Acceptability was assessed using a purpose-designed questionnaire.Findings: The median (IQR) volume of serum obtained using intracapillary sampling was 195µL (130-210). We showed drug level equivalence (slope [95% CI]: TEa vs observed mean % difference) between intracapillary sampling and conventional venepuncture for adalimumab (1·02 [0·90-1·14]: 11·7% vs 2·1%), infliximab (1·08 [0·98-1·18]: 18·3% vs 1·2%), vedolizumab (0·91 [0·85-0·96]: 17·6% vs 4·1%), and ustekinumab (0·92 [0·90-0·94]: 19·4% vs 3·3%). Anti-drug antibody equivalence was observed for anti-adalimumab (0·96 [0·95-0·98]: 24·5% vs 2·1%) and anti-infliximab (0·89 [0·81-0·97]: 17·3% vs 1·3%) antibody levels. Most patients reported that intracapillary testing was easy, convenient, and that they preferred it to conventional venepuncture.Interpretation: Low-volume intracapillary blood sampling was equivalent to conventional venepuncture for the measurement of biologic drug and anti-drug antibodies. Patients preferred intra-capillary testing to conventional venepuncture. Irrespective of future COVID-19 surges, patient-led intracapillary blood sampling is likely to become a key adjunct to telemedicine in patients with immune-mediated inflammatory diseases.Funding: Novo Nordisk Foundation. NIHR Exeter Clinical Research Facility. The Academic Department of Blood Sciences, RDE NHS Trust.Declaration of Interests: All authors have completed the ICMJE Form for Disclosure of Potential Conflicts of Interest and declare: D.C received honoraria from Ferring and Pfizer outside of this work; N.A.K has consulted for Falk and received honoraria from Falk, Allergan, Pharmacosmos and Takeda for unrelated topics and is a deputy editor of Alimentary Pharmacology & Therapeutics Journal; T.A has received unrestricted research grants, advisory board fees, speaker honorariums and support to attend international meetings from AbbVie, Merck, Janssen, Takeda, Ferring, Tillotts, Ferring, Pfizer, NAPP, Celltrion, Hospira for unrelated topics, no financial relationships with any organizations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work. R.N, B.H, E.J, S.H, C.R, V.C, K.P, J.R.G and T.J.M have no conflicts of interest to declare.Ethics Approval Statement: The sponsor was the Royal Devon and Exeter NHS Foundation Trust and the South West Research Ethics Committee approved the study (IRAS Reference Number: 286396; July 2020).

Optimisation of vancomycin exposure in neonates based on the best level of evidence

There is no consensus regarding optimal dosing of vancomycin in term or preterm neonates. Various available dosing recommendations are based on age, kidney function and/or body weight to define a starting dose. Our objectives were (i) to develop a comprehensive population PK model of vancomycin in a large cohort of neonates and (ii) to evaluate and compare the performances of current dosing approaches with respect to target attainment, using simulations based on our model. This will serve the purpose to recommend the best dosing approaches among existing regimens in the early and later phases after treatment initiation as a complementary approach to therapeutic drug monitoring (TDM).A total 405 neonates provided 1831 vancomycin concentrations measured during routine TDM. A one-compartment model with linear elimination incorporating covariates such as age, kidney function and body weight was developed (NONMEM®). The final model was applied to simulate in our population vancomycin exposure resulting from 20 dosing guidelines identified in the literature. Proportions of patients within and above target exposure were used as a performance measure. Target attainment meant area under the curve/minimal inhibitory concentration (AUC24/MIC) ratio of 400–700 h and trough concentration of 10–20 mg/L, both on days 1 and 7.Most current vancomycin dosing regimens fail to ensure target attainment in a majority of neonates. Insufficiently dosed regimens should be avoided, especially in centers with widespread coagulase negative Staphylococci. Adding a loading dose to simple regimens is best recommended to increase the proportion of early target attainment. Complex regimens seem to marginally improve exposure.Optimisation of efficacy while minimizing toxicity of vancomycin in neonates is needed. The application of a simple dosing regimens like NNF7 or the Neofax Hi-Dose regimens, with a 25 mg/kg loading dose for severe infections, or the SmPC regimen should be recommended to ensure the highest proportion of target attainment after 24 h. TDM should then be carried out, to account for residual unexplained variability in vancomycin elimination.

417. Clinical Mycology in Latin America and the Caribbean: Diagnostic Capabilities and Antifungal Therapy

BackgroundNo data are available about diagnostic capabilities and practice in clinical mycology in Latin America and the Caribbean.MethodsHere, we conducted an online survey aimed to assess availability, routine diagnostic procedures and access to therapy. Contacts were made through LIFE initiative (Leading International Fungal Education), SBI (Brazilian Society of Infectious Diseases), SBAC (Brazilian Society of Clinical Analysis), and SBM (Brazilian Society of Microbiology) during the first 2018 trimester.ResultsWe got 128 responses, each one from a single healthcare institution. Countries included Brazil (96), Mexico (9), Colombia (5), Uruguay (3), Guatemala (3), Argentina (2), Chile (2), Paraguay (2), Venezuela (2), Barbados (1), Ecuador (1), Honduras (1), and Peru (1). Most frequent institution profiles were public (38%), private (14%), and university hospitals (22%). Number of hospital beds varied between 12–3,000 (median 200 beds). ICU beds ranged 3–500 (15 beds). Most institutions provided care for hematology (63%) and HIV (31%) patients. Yeast identification was performed by biochemical tests (76%), automated methods (65%), and MALDI-TOF (15%). Twelve percent of responders had access to DNA sequencing. Almost a half (39%) of institutions did not undertake antifungal susceptibility tests, 47% did it only for yeasts, 2% molds. Fifteen (12%) institutions performed antifungal susceptibility tests routinely for all fungal isolates. Automated methods were the most frequently used antifungal susceptibility methodology (38%). Eighty-two (64%) institutions had no access to therapeutic drug monitoring (TDM). Cryptococccal antigen testing was available for 75% of responders.ConclusionThis survey was the largest and most updated snapshot of the clinical mycology scenario in Latin America and Caribbean. Efforts should be made to improve diagnostic capabilities and equalize regional disparities.Disclosures All authors: No reported disclosures.

The validation of an LC-MS/MS assay for perhexiline and major hydroxy metabolites, and its application to therapeutic monitoring in patient plasma.

Perhexiline (PEX), being developed to treat hypertrophic cardiomyopathy, is toxic at levels above the therapeutic range. Plasma level monitoring is therefore essential. The absence of a UV-absorbing chromophore has in the past required quantitative analysis of PEX in plasma using lengthy derivatization methods, followed by HPLC and fluorescence detection. The routine and urgent analysis of a large number of patient plasma samples necessitates faster and reliable analytical methodology. An LC-MS/MS method, using two novel internal standards, has been validated for the quantitative measurement of PEX and its major hydroxy metabolites in human plasma. The assay has been applied to therapeutic drug monitoring (TDM), where PEX and the ratio of the drug to cis-hydroxy perhexiline, were measured at designated intervals.

Intravenous phenytoin: a retrospective analysis of Bayesian forecasting versus conventional dosing in patients

In the hospital, medication management for effective antiepileptic therapy with phenytoin (PHT) often needs rapid IV loading and subsequent dose adjustment according to therapeutic drug monitoring (TDM). To investigate PHT performance in reaching therapeutic target serum concentration rapidly and sustainably, a Bayesian forecasting (BF) regimen was compared to conventional dosing (CD), according to the official summary of product characteristics. A 500-600 bed acute care teaching hospital in Switzerland, serving as a referral centre for neurology and neurosurgery. In a retrospective, single centre, long-term analysis of hospitalized in- and out-patients, all PHT serum tests from the central hospital laboratory from 1997 to 2007 were assessed. The BF regimen consisted of a guided, body weight-adapted rapid IV PHT loading over 5 days with pre-defined TDM time points. The conventional dosage was performed without written guidance. Assuming non-normally distributed data, non-parametric statistical methods for analysis were applied. The extent of target therapeutic PHT serum levels (40-80 μmol/L) was measured and compared between the two regimens. Also, the influence of gender and age was analysed. A total of 6,120 PHT serum levels (2,819 BF and 3,301 conventionally dosed) from 2,589 patients (869 BF and 1,720 conventionally dosed) were evaluated and compared. 63.6 % of the PHT serum levels from the BF group were within the therapeutic range, compared with only 34.0 % in the conventional group (p < 0.0001). The mean BF serum level was 52.0 ± 22.1 μmol/L (within target range) (n = 2,819), whereas the mean serum level of the CD was 39.8 ± 28.2 μmol/L (sub-target range) (n = 3,301). In the BF group, men had small but significantly lower PHT serum levels compared to women (p < 0.0001). The conventionally dosed group showed no significant gender differences (p = 0.187). A comparative sub-analysis of age-related groups (children, adolescents, adults, seniors, and elderly) showed significantly lower target levels (p < 0.0001) for each group in the conventional dosed group, compared to BF. Comparing the two cohorts, BF with the well-defined dose regimen showed significantly better performance in reaching therapeutic PHT serum levels rapidly and for longer duration.

Outcomes in patients with gram-negative sepsis treated with gentamicin.

Recent changes to therapeutic drug monitoring (TDM) of gentamicin have been advocated in Australia. It remains uncertain whether these will have an effect on hard clinical endpoints. The aim of this study was to determine clinical outcomes in patients with gram-negative infections treated with gentamicin. Microbiology results of patients with confirmed gram-negative cultures were retrospectively reviewed and those treated with gentamicin included. Medical records were reviewed and patient demographics, diagnosis, renal function, comorbidities, gentamicin doses, duration, monitoring, concomitant antibiotics, antimicrobial sensitivity and clinical and microbiological outcomes recorded. A total of 100 patients were included in the study: 52% were male, median age 64 years (17-97). Total body weight was recorded in 56% (median 74.5 kg, range 35-134 kg). Most patients had two or more important comorbidities. A total of 72% received empiric and 28% directed treatment. The organism was identified on blood culture in 45%, urine culture in 43% and aspiration of liver abscess in 12%; 95% of organisms were sensitive to gentamicin. Baseline renal function was normal in 62%. Mean gentamicin dose was 3.9 ± 0.9 mg/kg and mean duration 2.9 ± 2.5 days. Only 21% had optimal TDM. Clinical outcome was favourable in 90%. There were no cases of preventable serious toxicity. Despite the modest doses of gentamicin used in an elderly population with comorbidities, as well as the absence of optimal TDM, outcomes were favourable without preventable serious toxicity.

Variation in gentamicin and vancomycin dosage and monitoring in UK neonatal units

Gentamicin and vancomycin are commonly used in neonatal units for the treatment of life-threatening infections. This study aimed to describe the dosage regimen and the approach to therapeutic drug monitoring (TDM) for both antibiotics in units that participate in a UK neonatal network. Questionnaires were sent to all units across the Extended Neonatal Network, requesting details of each unit's dosing regimen and TDM practice. A total of 43 (of 114) units replied to the gentamicin questionnaire and 29 to the vancomycin questionnaire. Ten different gentamicin dosing regimens were used, depending on gestational age and weight. Most units (79%) followed British National Formulary for Children dosing guidance regarding vancomycin, but there were nine variations in TDM practice. There is significant variation in gentamicin and vancomycin dosing regimens and TDM guidance across a UK network of neonatal units. The development of standardized, evidence-based protocols should be prioritized.

Successful Efavirenz Dose Reduction Guided by Therapeutic Drug Monitoring

There are potential benefits to individualizing dosage in patients treated with efavirenz (EFV). We tested a simplified algorithm based on a Bayesian pharmacokinetic approach for guiding dose reduction in patients with EFV concentrations above the 75th percentile (P75) with documented virological efficacy. We designed a prospective, open-label, multicentre study. All consenting participants with EFV concentrations above P75 on standard dosage were included in a dose-reduction cycle. Primary end point was the number of patients who reached plasma concentrations within target (1,000-4,000 ng/ml) after, at most, two cycles of dose reduction at 3 and 6 months. CYP2B6 genetic characterization was performed. Seventy-two patients were screened and 13 fulfilled selection criteria. These patients, with undetectable viraemia on a stable 600 mg EFV-based regimen, had a median (interquartile range) EFV plasma level of 8,112 ng/ml (5,993-10,278) at baseline; 38% (between P75 and P95) qualified for a 400 mg EFV dose, and 62% (above P95) qualified for a 200 mg EFV dose. After one to two dose-reduction cycles, all patients reached targets for EFV plasma concentration at 24 weeks. The predictive dose reduction based on genetic profile differed from dose reduction according to therapeutic drug monitoring (TDM) in three patients. All patients maintained viral suppression at 6 months. A standardized TDM-guided EFV dose-reduction strategy over a 24-week period was successful, safe and yielded EFV plasma concentrations within the recommended therapeutic range. In addition to improving neuropsychiatric tolerability, EFV dose reduction has the potential to substantially decrease treatment cost.

Influence of P-glycoprotein (P-gp) induction on the pharmacokinetics of risperidone and paliperidone in mouse brain

P-glycoprotein (P-gp) is responsible for active efflux of drugs at the blood-brain barrier (BBB). With this study we wanted to investigate the consequences of P-gp induction on the pharmacokinetics of the known P-gp substrates risperidone and its active metabolite 9-OH-risperidone (paliperidone) in P-gp wildtype (WT) mice (FVB/N) and double-knockout (KO) mice (mdr1a/1b -/-/-/-). We used the known P-gp inducing substances dexamethasone (50mg/kg/d) and 5-pregnene-3beta-ol-20-one-16alpha-carbonitrile (PCN) (25mg/kg/d) for our study and injected them i.p. for 4 days. As controls solvent only was injected. On day 5 risperidone (3mg/kg) was i.p. injected. 1, 3 and 6h after the risperidone injection brain levels of risperidone and paliperidone were analysed using a reversed phase high performance liquid chromatography (RP-HPLC) method. The active moiety, sum of risperidone and paliperidone, were calculated due to their similar receptor profile and pharmacological effect with respect to therapeutic drug monitoring (TDM) standards. The results demonstrate the outstanding influence of transporter proteins in the disposition of risperidone and paliperidone. Brain levels of the active moiety were significantly changed in both induction groups. Both inducers showed distinct decreases in the area-under-the-data (AUD) and the brain versus plasma (B/P) ratios. But the results of the KO mice and the risperidone vs. 9-OH-risperidone (RIS:9-OH-RIS) ratios suggest that other mechanisms must be involved.

Therapeutic drug monitoring: an e-learning resource

The main aim of this project was to produce an interactive e-learning resource explaining the pharmacokinetic principles related to therapeutic drug monitoring (TDM). The target audience for the resource were scientists at Manchester Royal Infirmary and the intended learning outcome for the users was to improve their understanding of the pharmacology behind the results they generate. The null hypothesis stated that the resource would not cause a significant improvement in the users' understanding of pharmacokinetics. The ADDIE Instructional Design Model was applied to the learning situation. A pre-project questionnaire allowed for a needs analysis to be conducted, determining the current level of knowledge. Design and development involved production of project plans and story- boards and the entire resource was produced using Opus Professional. The resource was distributed via compact discs, along with pre- and post-resource questionnaires to permit analysis. Knowledge was compared before and after using the resource to establish the effectiveness of the resource, and the functionality of the resource was evaluated. The needs questionnaire results outlined the exist- ing level of knowledge as being varied and provided suggestions for possible concepts to include in the resource. A more precise and accurate definition of TDM, why it is carried out, and the pharmacokinetic parameters were apparent in the post-resource questionnaire results. Confidence in the understanding and interpretation of data produce was not significantly improved (Wilcoxon matched pairs signed ranks test, n ¼ 14, P ¼ 0.13), while confidence in the understanding of pharmacokinetic parameters was significantly improved (Wilcoxon matched pairs signed ranks test, n ¼ 16, P ¼ 0.01). About 81% of the audience found the resource very helpful to understand- ing TDM and all of the users found it either easy to use or very easy to use. The post-resource results showed that confidence in the understanding of pharmacokinetics was improved, indicating that the learning outcomes of the user were achieved thus allowing the null hypothesis to be rejected. However, confidence in understanding the data generated was not improved, suggesting a possible aspect to be developed if the project was to be repeated. Functionality of the resource was successful as users found the resource easy to use and navigate.