Therapeutic drug monitoring in inflammatory bowel disease: A practical approach

The global burden of inflammatory bowel diseases (IBD) is estimated at 4.9 million and the global prevalence exceeds 0.3%. Multiple newer therapeutic agents have broadened the options for the therapy of IBD in the last three decades. Thiopurines, however, have retained their place as maintenance therapy in IBD, especially in resource-constrained setting. But thiopurines have narrow therapeutic range, often needing discontinuation due to side effects or lack of efficacy. Biologic agents revolutionized the treatment of IBD, but the efficacy is lost in 50% of patient after one year. These outcomes are often due to inadequate drug concentrations that may lead to the development of antibodies as well as pharmacodynamic failure. Therapeutic drug monitoring (TDM) was proposed to reduce loss of response and to optimize the therapy in patients on thiopurine and biologic therapy. TDM is based on exposure-response relationship, suggesting a positive correlation between elevated serum anti-TNF concentrations and favorable therapeutic outcomes. TDM has multiple facets. This article discusses the benefits, evidence and limitations of TDM. The practical use of TDM in clinical practice is highlighted. Newer developments in the field and their relevance in practice are discussed.

Therapeutic drug monitoring in childhood idiopathic nephrotic syndrome: a state of the art review

Immunosuppressants are commonly used as steroid-sparing agents in childhood idiopathic nephrotic syndrome (NS) to induce and sustain remissions. These drugs have narrow therapeutic indices with high inter- and intra-patient variability. Therapeutic drug monitoring (TDM) would therefore be essential to guide the prescription. Multiple factors in NS contribute to additional variability in drug concentrations, especially during relapses. In this article, we review the currently available evidence of TDM in NS and suggest a practical approach for clinicians' reference.

The usefulness of Olanzapine plasma concentrations in monitoring treatment efficacy and metabolic disturbances in first-episode psychosis

INTRODUCTION

The role of Olanzapine therapeutic drug monitoring is controversial. The present study explores the associations of Olanzapine plasma concentrations with clinical response and metabolic side effects in first episode psychosis (FEP) after 2 months of treatment.

METHODS

Forty-seven patients were included. Improvement in clinical symptomatology was assessed using the PANSS. Metabolic assessment included weight, blood pressure, waist circumference, blood glucose, total cholesterol, high-density lipoprotein, low-density lipoprotein, and triglycerides.

RESULTS

The Olanzapine plasma concentrations after 2 months of treatment were positively correlated with weight gain (r = 0.49, p = 0.003), and a concentration > 23.28 ng/mL was identified as a positive predictor of weight gain (≥ 7%). The Olanzapine concentration to dose (C/D) ratio was positively correlated with the percentage of improvement in the total PANSS (r = 0.46, p = 0.004), and a C/D ratio > 2.12 was identified as a positive predictor of a good response (percentage of improvement > 30%) after 2 months of treatment. We also identified several factors that could alter Olanzapine pharmacokinetics: gender (p = 0.03), diagnosis (p = 0.05), smoking habit (p = 0.05), and co-medications such as valproic acid (p = 0.05) and anxiolytics (p = 0.01).

DISCUSSION

In conclusion, our results suggest that therapeutic drug monitoring of Olanzapine could be helpful to evaluate therapeutic efficacy and metabolic dysfunction in FEP patients treated with Olanzapine.

Optimizing the correct timing of vancomycin level collection utilizing a vancomycin medication administration record (MAR) level order

OBJECTIVE

Vancomycin, a commonly used antimicrobial, has a narrow therapeutic index; therefore, Therapeutic Drug Monitoring (TDM) is required. Although the Electronic Medical Record (EMR) may improve patient care, without appropriate optimization, it can contribute to incorrectly drawn vancomycin levels. For medication administration, nurses utilize the Medication Administration Record (MAR) for medication administration documentation and medication workflow guidance. Therefore, we hypothesized creating a MAR level order which would be incorporated into this already established medication workflow may improve the rate of correctly drawn vancomycin levels.

MATERIALS AND METHODS

This was a multicenter, retrospective, pre-and post-intervention study which evaluated the effect of a Medication Administration Record (MAR) level order within the EMR on the correct timing of vancomycin level collection. Vancomycin levels were classified into pre-and post-intervention groups. The primary endpoint was the rate of incorrectly drawn levels, defined as a level being drawn early, a level being drawn late, a level drawn while infusing, or a missed level.

RESULTS

A total of 1353 vancomycin levels were assessed, and 628 levels met inclusion criteria. Of the levels eligible for inclusion, 331 were in the pre-intervention period and 297 were in the post-intervention period. Levels in the post-intervention group utilizing the vancomycin MAR level order were less likely to be missed or drawn at an incorrect time (11.1 % vs 36 %, P < 0.01) and were less likely to require rescheduling (3.4 % vs 8.5 %, P < 0.01).

CONCLUSION

Utilization of a vancomycin MAR level order was associated with a significant decrease in incorrectly drawn vancomycin levels.

Determination of proflavine in rat whole blood without sample pretreatment by laser desorption postionization mass spectrometry

A novel pretreatment-free method involving laser desorption postionization (LDPI) coupled with time-of-flight mass spectrometry (MS) was developed for the monitoring of proflavine level in rat whole blood. It comprises a protocol for dosing via intravenous administration and collection of whole blood, followed by direct LDPI-MS analysis without any sample pretreatment. An intense ion signal at m/z 209 was observed from whole blood without any interference signals, except some background signals below m/z 100. The calibration curve was established with use of 9-phenylacridine as the internal standard for proflavine determination from the plotting of the peak ratios of proflavine to the internal standard, with a correlation coefficient (R ²) greater than 0.99. The limit of detection was estimated to be 0.48 pmol/mm² and the quantification range was 0.5-16.5 μg/mL for proflavine. In addition, only a minimal matrix effect was observed, as expected from considerations of the desorption and ionization mechanism. Interday and intraday accuracy and precision were calculated to be within 13% and 82-114%, respectively. Estimated concentrations of proflavine residue in whole blood were also successfully obtained at selected time points after dosing. The proposed method is simple, low cost, and sensitive, and should be seen as a complementary method for monitoring drug levels in blood. Graphical Abstract Monitoring proflavine levels in rat whole blood at different time points using laser desorption postionization mass spectrometry (LDPI-MS).

Adjuvant and salvage therapy with leflunomide for recalcitrant cytomegalovirus infections in hematopoietic cell transplantation recipients: A case series

Cytomegalovirus (CMV) reactivation is a clinically significant complication in hematopoietic stem cell transplant (HCT) recipients. Alternative therapy for multidrug-resistant CMV is limited and often fails. Leflunomide has been used to treat resistant CMV infections, however, data on efficacy, safety, and guidance for therapeutic drug level monitoring are lacking. In this report, we describe 3 HCT recipients with multi-drug resistant CMV infections who received leflunomide as adjuvant and salvage therapy. The therapeutic effect of leflunomide as an anti-CMV agent based on virologic responses and therapeutic drug monitoring were evaluated.

Therapeutic drug monitoring in patients with inflammatory bowel disease

Thiopurine analogs and anti-tumor necrosis factor (TNF) agents have dramatically changed the therapeutics of inflammatory bowel diseases (IBD), improving short and long-term outcomes. Unfortunately some patients do not respond to therapy and others lose response over time. The pharmacokinetic properties of these drugs are complex, with high inter-patient variability. Thiopurine analogs are metabolized through a series of pathways, which vary according to the patients' pharmacogenetic profile. This profile largely determines the ratios of metabolites, which are in turn associated with likelihoods of clinical efficacy and/or toxicity. Understanding these mechanisms allows for manipulation of drug dose, aiming to reduce the development of toxicity while improving the efficacy of treatment. The efficacy of anti-TNF drugs is influenced by many pharmacodynamic variables. Several factors may alter drug clearance, including the concomitant use of immunomodulators (thiopurine analogs and methotrexate), systemic inflammation, the presence of anti-drug antibodies, and body mass. The treatment of IBD has evolved with the understanding of the pharmacologic profiles of immunomodulating and TNF-inhibiting medications, with good evidence for improvement in patient outcomes observed when measuring metabolic pathway indices. The role of routine measurement of metabolite/drug levels and antibodies warrants further prospective studies as we enter the era of personalized IBD care.

Comparison of three a-priori models in the prediction of serum lithium concentration

Context:

Mathematical models are valuable for optimizing drug dose and dosing regimens.

Aims:

To compare the precision and bias of three a-priori methods in the prediction of serum level of lithium in patients with bipolar disorder, and to determine their sensitivity and specificity in detecting serum lithium levels outside the therapeutic range.

Settings and Design:

Hospital-based, retrospective study.

Materials and Methods:

In a retrospective study of 31 in-patients, the serum level of lithium was calculated using three different a-priori methods. Mean Prediction Error was used as a measure of bias while Mean Absolute Error and Root Mean Squared Error were used as a measure of precision. The sensitivity and specificity of the methods was calculated.

Results:

All three models underestimated serum lithium level. Precision was best with the model described by Pepin et al., while bias of prediction was the least with the method of Abou Auda et al. The formula by Pepin et al. was able to predict serum lithium level with a mean error of 36.57%. The sensitivity and specificity of the models in identifying serum lithium levels outside the therapeutic range was 80% and 76.19% for Pepin et al., 90% and 74.19% for Zetin et al., and 90% and 66.67% for Abou-Auda et al., respectively.

Conclusion:

The study demonstrates the difference in precision and bias of three a-priori methods, with no one method being superior to the other in the prediction of serum concentration.