Ethosuximide lowers lamotrigine serum concentrations: Evidence for a clinically relevant interaction.

We investigated the effect of comedication with ethosuximide (ESM) on lamotrigine (LTG) blood levels. Based on observations from clinical practice, we hypothesized that ESM reduces the LTG serum concentration. We additionally evaluated this effect in the presence of concomitant valproic acid (VPA). We retrospectively analyzed samples of inpatients from our department who had been treated with a combination of ESM and LTG between 2017 and 2021. We additionally used data on LTG serum concentrations from a previously published cohort from our center. Generalized estimation equations (GEEs) were used for statistical analyses. We included 523 samples from 209 patients. GEE analyses showed that LTG trough serum concentrations were significantly lower in samples with ESM comedication and significantly higher in samples with concomitant VPA. The effect of ESM was moderated by patients' age; in children and adolescents, LTG serum concentrations were 37% lower than in samples without ESM, whereas in adults, LTG serum concentrations were 14% lower. The effect we found in our data is relevant to daily clinical practice, if patients are not seizure-free despite typical daily LTG dosage, or if they develop side effects during ESM withdrawal. It should be considered especially in children and adolescents.

Adalimumab Dose Reduction and Withdrawal in Stable Non-Infectious Pediatric Uveitis: An Open-Label, Prospective, Pilot Study.

PURPOSES: This study investigated the feasibility of adalimumab (ADA) dose reduction and withdrawal strategy in children with stable pediatric non-infectious uveitis (PNIU). METHODS: This open-label prospective pilot trial recruited 18 stable PNIU patients (33 eyes) between two and eighteen years old who were treated with standard doses of ADA (20/40 mg every 2 weeks) plus oral methotrexate. The interval of ADA injection was extended to 4 weeks and followed up for 24 weeks. If the uveitis remained stable, ADA was discontinued and followed up for another 24 weeks. ADA was considered successfully stopped if no relapse occurred during this period. The relapse-free survival rate, best corrected visual acuity (BVCA), anterior chamber cell (ACC), vitritis, macular thickness (MT), and serum ADA levels were evaluated. Approval Number: 2021KYPJ201. ClinicalTrials.gov identifier: NCT05155592. RESULTS: The relapse-free survival rate was 22.2% (4/18) at 48 weeks. 33.3% (6/18) of patients relapsed when ADA was given every 4 weeks, while 44.5% of patients (8/18) relapsed after ADA was stopped. The four patients successfully withdrawn from ADA were all diagnosed with BD. No statistically significant differences (p > 0.05) were observed in BCVA and MT between baseline and final follow-up. The proportion of ACC and vitritis exhibited an upward trend (p < 0.05) during follow-up. Serum ADA gradually decreased to zero during follow-up in both non-recurrence and recurrence groups. CONCLUSIONS: In PNIU children who reached remission for 6 months, ADA dose reduction and withdrawal were associated with a high risk of inflammation recurrence. Timely adjustment of ADA to the last effective dosage frequency can regain control of the inflammation. Detection of ADA serum levels in patients with recurrence may help find the appropriate interval of ADA use.

Overcoming provider barriers to therapeutic drug monitoring of tumour necrosis factor inhibitors for rheumatoid arthritis: a qualitative analysis.

Objective: Therapeutic drug monitoring (TDM) of tumour necrosis factor-α inhibitors (TNFi), by measuring drug levels and/or anti-drug antibodies, is being considered by various international bodies to improve patient health outcomes and the value of care for people with rheumatoid arthritis. Rheumatology care providers may perceive barriers to adopting TNFi TDM within their own clinical practice, limiting the potential for patients and health care systems to benefit. This study aimed to explore the barriers perceived by rheumatologists that may reduce their uptake of TNFi TDM for rheumatoid arthritis. Method: Semi-structured one-to-one telephone interviews were performed with a convenience sample of senior rheumatologists with experience of managing people with rheumatoid arthritis. The interviews explored the rheumatologists' understanding of TDM and their beliefs about how it can be integrated into their own routine practice. Interviews were audio recorded, transcribed verbatim and anonymized. Transcripts were coded inductively and barriers to using TNFi TDM were identified by thematic framework analysis. Result: A sample of eleven senior rheumatologists were interviewed. The rheumatologists described five barriers to adopting TNFi TDM in routine practice: (i) observing clinical need; (ii) understanding how testing can improve practice; (iii) insufficient clinical evidence; (iv) insufficient resources to pay for testing; and (v) insufficient capability to deliver testing. Conclusion: Barriers to adopting TNFi TDM in routine care settings will restrict the ability for patients to benefit from effective monitoring strategies as they begin to emerge. Strategies to overcome these barriers are suggested which will require a coordinated response from stakeholders across health care systems.

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.

Impact of cerebral small vessel disease burden and drug level at admission on direct oral anticoagulant associated intracerebral hemorrhage.

INTRODUCTION: Direct oral anticoagulant (DOAC)-associated intracerebral hemorrhage (ICH) is a catastrophic complication. The aim of this study was to investigate the association between computed tomography (CT)-based cerebrovascular small vessel disease (SVD) burden and DOAC-ICH as well as the DOAC concentration upon hospital admission and ICH outcome. PATIENTS AND METHODS: The study included two cohorts: (1) DOAC-ICH: patients who suffered from DOAC-ICH and underwent drug level measurements upon admission; (2) DOAC-non-ICH: stable DOAC users who underwent head CT without ICH during treatment. We categorized the DOAC levels of the DOAC-ICH patients as low (<50 ng/mL), medium (50-300 ng/mL), and high (>300 ng/mL). The CT-based SVD burden (including white matter lesions [WML], lacunes, and cerebral atrophy) was evaluated, and SVD scores (range, 0-3) were used to evaluate SVD severity. RESULTS: A total of 43 DOAC-ICH patients and 177 DOAC-non-ICH patients were enrolled. DOAC-ICH patients were more likely to have WML, lacunes, or cerebral atrophy compared to DOAC-non-ICH patients. After adjustment, the SVD burden was associated with DOAC-ICH, with a higher risk of more severe SVD (SVD score of 2; odds ratio [OR], 10.3 [3.17, 33.3]; score of 3; OR, 16.8 [4.50, 62.6]). The proportions of patients with high, medium, and low drug levels in the DOAC-ICH group were 16.3%, 55.8%, and 27.9%, respectively. Additionally, the high-level group displayed a larger hematoma size and had worse functional outcomes at 3 months than the other two groups. DISCUSSION AND CONCLUSION: The severity of SVD burden was associated with DOAC-ICH. Furthermore, high DOAC levels in ICH were associated with unfavorable clinical outcomes. To address the potential selection bias from these two cohorts, a prospective study to investigate the co-contribution of drug levels and SVD to DOAC-ICH is essential.

A Case Series of 11 Patients With Subacute Serotonin Syndrome.

BACKGROUND: Serotonin syndrome is an acute, life-threatening illness characterized by mental status changes, neuromuscular symptoms, and autonomic instability. Some patients taking serotonergic antidepressants have been noted to have unexplained mental status changes and/or neuromuscular changes without autonomic instability raising the possibility of a more chronic or attenuated form of serotonin syndrome. OBJECTIVE: Assessment of antidepressant blood levels to support the diagnosis of a subacute serotonin syndrome. METHODS: At a tertiary psychiatric outpatient clinic, patients with unexplained mental status and/or neuromuscular changes without autonomic instability had antidepressant blood levels assessed. RESULTS: Eleven patients were identified with signs and symptoms partially consistent with serotonin syndrome. Nine patients had cognitive changes, while four patients had motor changes, and three patients had psychosis. All patients had elevated blood levels of a single serotonergic antidepressant. Limited follow-up suggests that symptoms improve with reduction of antidepressant medication. CONCLUSIONS: These cases suggest that a more chronic, attenuated form of serotonin syndrome exists. Diagnostic criteria are proposed for a distinct clinical entity: subacute serotonin syndrome (SSS). Further research is required to validate these criteria. Clinicians should consider drawing antidepressant levels for patients with symptoms and signs suggestive of SSS-especially those at increased vulnerability for excessive serotonergic agonism. Given the high prevalence of antidepressant medication use, the awareness of SSS could lead to improved patient outcomes and public health.

Unresolved issues in the use of direct acting oral anticoagulants.

INTRODUCTION: Currently approved direct oral anticoagulants (DOACs) target thrombin or coagulation factor Xa. Administered in fixed doses without routine laboratory monitoring, DOACs have simplified the approach to oral anticoagulation, when previously the choice was limited to vitamin K antagonists (VKAs). AREA COVERED: We discuss a) unresolved issues related to optimal use of DOACs and b) new developments including the potential for FXIa inhibitors to be effective and safer anticoagulants. EXPERT OPINION: By simplifying oral anticoagulation, DOACs have facilitated the uptake of anticoagulation. The DOACs are approved for stroke prevention in atrial fibrillation and for the prevention and treatment of venous thromboembolism, and their indications are expanding to include the prevention of atherothrombosis. DOACs have now replaced vitamin K antagonists (VKAs) for most indications, but not all. DOACs are inferior to VKAs for patients with mechanical heart valves, left ventricular assist device, rheumatic atrial fibrillation, and those with antiphospholipid syndrome, and their safety and efficacy are uncertain in some populations (e.g. advanced renal and liver disease). Impediments to use include concerns for bleeding and cost. The newly developed FXIa and FXIIa inhibitors have the potential to be safer than current anticoagulants, but phase 3 trials are needed to confirm their clinical efficacy and safety.

Adalimumab serum levels and anti-drug antibodies: associations to treatment response and drug survival in inflammatory joint diseases.

OBJECTIVES: To explore associations between serum adalimumab level, treatment response and drug survival in order to identify therapeutic drug levels for therapeutic drug monitoring of adalimumab. Also, to assess occurrence and risk factors of anti-drug antibody (ADAb) formation. METHODS: Non-trough adalimumab and ADAb levels were measured by automated fluorescence assays in serum collected after 3 months of adalimumab treatment in patients with rheumatoid arthritis (RA), psoriatic arthritis (PsA) or axial spondyloarthritis (axSpA) included in the observational NOR-DMARD study. Treatment response was evaluated after 3 months, and drug survival during long-term follow-up. RESULTS: In 340 patients (97 RA, 69 PsA, 174 axSpA), median adalimumab level was 7.3 mg/l (IQR 4.0-10.3). 33 (10%) patients developed ADAb. Findings were comparable across diagnoses. In RA and PsA, adalimumab levels ≥6.0 mg/l were associated with treatment response (Odds Ratio [OR] 2.2 [95% CI 1.0, 4.4]) and improved drug survival (Hazard Ratio [HR] 0.49 [0.27, 0.80]). In axSpA, a therapeutic level could not be identified, but higher adalimumab levels were associated with response. Factors associated with ADAb formation were previous bDMARD use, no methotrexate comedication and use of adalimumab originator compared with GP2017. CONCLUSION: Higher adalimumab levels were associated with better response and improved drug survival for all diagnoses, with a suggested lower threshold of 6.0 mg/l for RA/PsA. This finding, the large variability in drug levels among patients receiving standard adalimumab dose, and the high proportion of patients developing ADAb, encourages further investigations into the potential role of therapeutic drug monitoring of adalimumab.

Optimal Use and Need for Therapeutic Drug Monitoring of Teicoplanin in Children: A Systematic Review.

BACKGROUND: Teicoplanin is a glycopeptide antimicrobial that treats serious invasive infections caused by gram-positive bacteria, such as the methicillin-resistant Staphylococcus aureus. Despite some comparable advantages, there is no guideline or clinical recommendation for teicoplanin in the pediatric population, unlike vancomycin where abundant studies and the recently revised guideline on therapeutic drug level monitoring (TDM) exist. METHODS: The systematic review was performed in accordance with the preferred reporting items for systematic reviews. Two authors (JSC and SHY) searched PubMed, Embase, and Cochrane Library databases using relevant terms independently. RESULTS: Fourteen studies were finally included with a total of 1,380 patients. TDM was available in 2,739 samples collected in the nine studies. Dosing regimens varied widely, and eight studies used recommended dosing regimens. Timing for measuring TDM was mostly 72-96 hours or longer after the initiation of the first dose, which was expected to be a steady-state. The majority of studies had target trough levels of 10 µg/mL or above. Three studies reported that the clinical efficacy and treatment success rate of teicoplanin was 71.4%, 87.5%, and 88%. Adverse events associated with teicoplanin use were described in six studies with a focus on renal and/or hepatic impairment. Except for one study, no significant relation was noted between the incidence of adverse events and trough concentration. CONCLUSION: Current evidence on teicoplanin trough levels in pediatric populations is insufficient due to heterogeneity. However, target trough levels with favorable clinical efficacy are achievable by recommended dosing regimen in the majority of patients.

The Long-Acting Cabotegravir Tail as an Implementation Challenge: Planning for Safe Discontinuation.

The long-acting feature of cabotegravir, an integrase-inhibitor highly effective in preventing acquisition of HIV in adolescents and adults, is both its greatest strength and a challenge to its implementation. Cab-LA is administered at 8-week intervals (after an initial loading dose) but has a long, variable drug "tail" that may leave users vulnerable to future drug resistance if they contract HIV during this critical period. The potential for cab-LA to meaningfully contribute to ending the HIV Epidemic is hindered by, among other factors, limited resources to guide patients and providers on how to safely discontinue injections. We suggest three key strategies to overcome this specific challenge: (1) Comprehensive patient education and counseling about the drug tail; (2) Training and coaching PrEP care teams, including clinical and non-clinical staff, on communication around the tail; (3) Adherence support strategies, including monitoring of cabotegravir drug levels after discontinuation, for a personalized medicine approach to safe discontinuation.

Efficacy and Safety of Vedolizumab in Patients with Inflammatory Bowel Disease in Association with Vedolizumab Drug Levels.

BACKGROUND: Vedolizumab (VDZ) is a well-established and important therapeutic option in the treatment of patients with inflammatory bowel disease (IBD). However, the significance of therapeutic drug monitoring (TDM) with VDZ remains a contradictory field in daily clinical practice. Our study aims to clarify the predictive impact of VDZ drug levels in long-term clinical outcomes in a real-world cohort. METHODS: Patients with moderate to severe ulcerative colitis (UC) and Crohn's disease (CD) from a tertiary IBD referral center at the University Hospital Augsburg, Germany, were enrolled in this single-center retrospective data analysis. Clinical and endoscopic data were collected at month 6, month 12, and at the last time of follow-up, and outcomes were correlated with VDZ levels at week 6. RESULTS: This study included 95 patients, 68.4% (n = 65) with UC, 24.2% (n = 23) with CD, and 7.4% (n = 7) with indeterminate colitis (CI). Patients with a mean VDZ treatment time of 17.83 months ± 14.56 showed clinical response in 29.5% (n = 28) and clinical remission in 45.3% (n = 43) at the end of the study. Endoscopic response occurred in 20.0% (n = 19) and endoscopic remission in 29.5% (n = 28) at the end of the study. The sustained beneficial effect of VDZ was also reflected in a significant change in biomarker levels. VDZ trough level at week 6 was determined in 48.4% (n = 46) with a mean of 41.79 µg/mL ± 24.58. A significant association between VDZ level at week 6 and both short and long-term outcomes could not be demonstrated. However, numerically higher VDZ levels were seen in patients with endoscopic and clinical improvement at month 6 and at the time of last follow-up. CONCLUSIONS: This study demonstrated efficacy and safety for VDZ in a real-world cohort. Although, for some parameters, a clear trend for higher VDZ levels at week 6 was seen, the efficacy of VDZ was not significantly correlated to VDZ level at week 6, which questions the predictive value of VDZ levels in the real world.

Pregabalin Add-On vs. Dose Increase in Levetiracetam Add-On Treatment: A Real-Life Trial in Dogs With Drug-Resistant Epilepsy.

Epilepsy is a common neurological disorder affecting 0.6-0.75% of dogs in veterinary practice. Treatment is frequently complicated by the occurrence of drug-resistant epilepsy and cluster seizures in dogs with idiopathic epilepsy. Only few studies are available to guide treatment choices beyond licensed veterinary drugs. The aim of the study was to compare antiseizure efficacy and tolerability of two add-on treatment strategies in dogs with drug-resistant idiopathic epilepsy. The study design was a prospective, open-label, non-blinded, comparative treatment trial. Treatment success was defined as a 3-fold extension of the longest baseline interseizure interval and to a minimum of 3 months. To avoid prolonged adherence to a presumably ineffective treatment strategy, dog owners could leave the study after the third day with generalized seizures if the interseizure interval failed to show a relevant increase. Twenty-six dogs (mean age 5.5 years, mean seizure frequency 4/month) with drug-resistant idiopathic epilepsy and a history of cluster seizures were included. Dogs received either add-on treatment with pregabalin (PGB) 4 mg/kg twice daily (14 dogs) or a dose increase in levetiracetam (LEV) add-on treatment (12 dogs). Thirteen dogs in the PGB group had drug levels within the therapeutic range for humans. Two dogs in the PGB group (14.3%; 2/14) and one dog in the LEV group (8.3%; 1/12) achieved treatment success with long seizure-free intervals from 122 to 219 days but then relapsed to their early seizure frequency 10 months after the study inclusion. The overall low success rates with both treatment strategies likely reflect a real-life situation in canine drug-resistant idiopathic epilepsy in everyday veterinary practice. These results delineate the need for research on better pharmacologic and non-pharmacologic treatment strategies in dogs with drug-resistant epilepsy.

Suboptimal vancomycin levels in critically ill children with sickle cell disease and acute chest syndrome.

OBJECTIVES: This is a pilot retrospective study to assess the effect of glomerular hyper-filtration (GHF) related to sickle cell disease (SCD) on vancomycin clearance and ultimately on therapeutic drug levels in children admitted to the pediatric intensive care unit (PICU) with acute chest syndrome (ACS). METHOD: The patients' steady-state vancomycin trough levels (VTL) and the area under the curve (AUC) were compared with those of age- and gender-matched control group; matching was made at a 1:3 ratio. RESULTS: Twelve SCD patients with ACS and treated with vancomycin were compared with 36 non-SCD patients (control group). Compared with the control patients, the ACS patients had significantly lower initial serum VTL (median = 6.00 mcg/mL vs. 9.75 mcg/mL) (p = 0.007), and their average VTL were still lower (median = 6.65 mcg/mL vs. 10.00 mcg/mL) post vancomycin dose adjustment (p = 0.039). The time to achieve the therapeutic vancomycin level was significantly longer for the ACS patients (median = 4.75 days) than for the control group (median = 1 day) (p = 0.009). The AUC was also significantly lower in the ACS patients (median = 293 mg*h/L) than in the control group (median = 405.5 mg*h/L) (p = 0.007). The AUC was negatively associated with creatinine clearance (Beta Coefficient = -0.366, p-value=<0.001) even when adjusted for receiving loading dose, standard dose per weight, and severity of critical illness. CONCLUSION: These findings support the attributed role of the GHF associated with SCD leading to lower vancomycin level in ACS cases. Therefore, the standard dosing approach for vancomycin in ACS patients may be ineffective. We thus advocate for individualized dosing with careful monitoring of drug levels to account for GHF.

Antiepileptic-drug tapering and seizure recurrence: Correlation with serum drug levels and biomarkers in persons with epilepsy.

OBJECTIVES: Antiepileptic-drug (AED) serum level and inflammatory biomarkers are primarily monitored/assessed during epilepsy treatment for effective seizure control; however, their correlation with seizure recurrence (SR) following AED-tapering has not been established, and this is being investigated in this study. MATERIALS AND METHODS: This prospective observational study enrolled persons with epilepsy (PWE) on AED monotherapy and going to start tapering after being seizure-free for ≥2 years. Data regarding seizure episodes, AED-treatment, and adverse events (using Liverpool Adverse Event profile [LAEP]-score) were recorded. Serum AED levels using high-performance liquid chromatography and biomarkers levels through enzyme-linked immunosorbent assay kits were estimated at AED-tapering commencement and at 6 months/SR time. RESULTS: Among 129 enrolled PWE (levetiracetam [n = 52], valproate [n = 34], carbamazepine [n = 29], and phenytoin [n = 14]), SR occurred in 23.3% during follow-up (range 12-44 months). PWE with subtherapeutic serum AED level at the onset of tapering had higher SR (P = 0.004) than those with therapeutic or higher levels. Levetiracetam-treated PWEs with SR have significantly low AED levels than PWE with no-SR (P < 0.001). PWE had significantly raised inflammatory biomarkers (interleukin [IL]-1 ß, tumor necrosis factor [TNF]-α, IL-6, and high-mobility group box protein 1) and decreased IL-10 than healthy control subjects. SR and no-SR groups did not differ significantly in inflammatory markers except for higher IL-1 ß and TNF-α levels in SR group (P = 0.001, 0.02, respectively). Improvement in LAEP score was observed in follow-up visits without any difference between SR and no-SR groups. CONCLUSION: Low serum AED levels (especially levetiracetam) and raised levels of TNF-α and IL-1 ß during tapering commencement had a higher association with SR following AED-tapering.

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.

Therapeutic Drug Level Monitoring of Teicoplanin in Korean Pediatric Patients with Normal versus Impaired Renal Function.

BACKGROUND: Teicoplanin is used to treat serious gram-positive infections. Optimal teicoplanin trough levels are considered to be ≥ 10 µg/mL. Despite its wide use in various clinical settings, data on teicoplanin trough level in pediatric patients are limited. Therefore, the aim of this study was to investigate the therapeutic drug level monitoring of teicoplanin in Korean pediatric patients, including those with impaired renal function. METHODS: A retrospective study was performed in pediatric patients (age ≤ 18 years old) who received teicoplanin from September 2014 to April 2018. The regimen included a loading dose of 10 mg/kg/dose at 12 hours' interval three times in a row, and a maintenance dose of 10 mg/kg/dose commenced at 24 hours of interval after the loading dose, with a maximum of 400 mg/dose, respectively. The first therapeutic drug levels were measured. Distribution and characteristics of trough levels in patients with decreased renal function and those with bacteremia were also assessed. RESULTS: A total of 187 trough levels were collected from 143 patients. Hematologic and oncologic diseases were the most common underlying diseases (83.2%, n = 119). One hundred eighty trough levels were first measured, and their median value was 16.2 µg/mL (range, 2.3-100 µg/mL) and the median interval between initial teicoplanin injection and 1st trough level was 96.5 hours (range 47.6-179.3 hours). Lower steady-state levels were observed in younger age group (median, 13.5 vs. 18.0 µg/mL, P = 0.038). Median trough levels were higher in patients with decreased renal functions (P < 0.001). In addition, among eight with gram-positive bacteremia, seven of them had a favorable outcome. CONCLUSION: This study provides additive information on trough level monitoring of teicoplanin in children with impaired renal function and treatment effect in patients with gram-positive bacteremia. Careful monitoring for steady state trough levels of teicoplanin is warranted.

Incentives conditioned on tenofovir levels to support PrEP adherence among young South African women: a randomized trial.

INTRODUCTION: HIV incidence remains high among African adolescent girls and young women (AGYW), who would benefit from pre-exposure prophylaxis (PrEP). Strategies to increase PrEP adherence and persistence need to be evaluated in African AGY, including incentives conditional on high adherence. METHODS: The 3Ps for Prevention Study was a 12-month prospective cohort of 200 women ages 16 to 25 initiating PrEP in South Africa from 2017 to 2018. Participants received retrospective feedback about drug levels at Months 1, 2 and 3; half was randomized to receive a 200 Rand shopping voucher ($13 US) at Months 2, 3 and 4, conditioned on high intracellular tenofovir diphosphate (TFV-DP) levels in dried blood spots (≥500 fmol/punch at Month 1, ≥700 fmol/punch at Months 2 and 3). The primary analysis was intention-to-treat, comparing the proportion with high PrEP adherence (≥700 fmol/punch) at Month 3 by randomized group, based on 100% efficacy among men who have sex with men. RESULTS: Median age of the 200 women was 19 years (interquartile range [IQR] 17, 21); 86% had a primary sexual partner. At Month 3, the mean TFV-DP level was 822 fmol/punch (SD 522) in the incentive group and 689 fmol/punch (SD 546) in the control group (p = 0.11). Forty-five (56%) of 85 women in the incentive group and 35 (41%) of 85 women in the control group had TFV-DP levels ≥700 fmol/punch (RR 1.35; 95% CI 0.98, 1.86; p = 0.067), which declined to 8% and 5% in the incentive and control groups at Month 12 (no significant difference by arm). 44% refilled PrEP without gaps, 14% had a gap of ≥3 weeks in coverage subsequently restarted PrEP and 54% accepted at the final dispensing visit at Month 9. No new HIV infections were observed after PrEP initiation. CONCLUSIONS: Among South African AGYW initiating PrEP, drug levels indicated high PrEP adherence in almost half of women at Month 3, with a non-statistically significant higher proportion with high adherence among those in the incentive group. Over half persisted with the 12-month PrEP programme although high adherence declined after Month 3. Strategies to support PrEP adherence and persistence and longer-acting PrEP formulations are needed.

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.

Drug level testing as a strategy to determine eligibility for drug resistance testing after failure of ART: a retrospective analysis of South African adult patients on second-line ART.

INTRODUCTION: When protease inhibitor (PI)-based second-line ART fails, guidelines recommend drug resistance testing and individualized third-line treatment. However, PI-resistant viral strains are rare and drug resistance testing is costly. We investigated whether less costly PI-exposure testing can be used to select those patients who would benefit most from drug resistance testing. METHODS: We performed a retrospective analysis of South African adults living with HIV experiencing failure of ritonavir-boosted-lopinavir (LPV/r)-based second-line ART for whom drug resistance testing results were available. We included patients who received plasma-based drug resistance testing at a central South African reference laboratory in 2017 and patients who received dried blood spots (DBS)-based drug resistance testing at a rural South African clinic between 2009 and 2017. PI-exposure testing was performed on remnant plasma or DBS using liquid chromatography mass spectrometry (LCMS). Additionally, a low-cost immunoassay was used on plasma. Population genotypic drug resistance testing of the pol region was performed on plasma and DBS using standard clinical protocols. RESULTS: Samples from 544 patients (494 plasma samples and 50 DBS) were included. Median age was 41.0 years (IQR: 33.3 to 48.5) and 58.6% were women. Median HIV-RNA load was 4.9 log10 copies/mL (4.3 to 5.4). Prevalence of resistance to the NRTI-backbone was 70.6% (349/494) in plasma samples and 56.0% (28/50) in DBS. Major PI-resistance mutations conferring high-level resistance to LPV/r were observed in 26.7% (132/494) of plasma samples and 12% (6/50) of DBS. PI-exposure testing revealed undetectable LPV levels in 47.0% (232/494) of plasma samples and in 60.0% (30/50) of DBS. In pooled analysis of plasma and DBS samples, detectable LPV levels had a sensitivity of 90% (84% to 94%) and a negative predictive failure of 95% (91% to 97%) for the presence of major LPV/r resistance. CONCLUSIONS: PI-exposure testing revealed non-adherence in half of patients experiencing failure on second-line ART and accurately predicted the presence or absence of clinically relevant PI resistance. PI-exposure testing constitutes a novel screening strategy in patients with virological failure of ART that can differentiate between different underlying causes of therapy failure and may allow for more effective use of limited resources available for drug resistance testing.

Enzymatic Assay for Rapid Measurement of Antiretroviral Drug Levels.

Poor adherence to pre-exposure prophylaxis (PrEP) and antiretroviral therapy (ART) can lead to human immunodeficiency virus (HIV) acquisition and emergence of drug-resistant infections, respectively. Measurement of antiviral drug levels provides objective adherence information that may help prevent adverse health outcomes. Gold-standard drug-level measurement by liquid chromatography/mass spectrometry is centralized, heavily instrumented, and expensive and is thus unsuitable and unavailable for routine use in clinical settings. We developed the REverSe TRanscrIptase Chain Termination (RESTRICT) assay as a rapid and accessible measurement of drug levels indicative of long-term adherence to PrEP and ART. The assay uses designer single-stranded DNA templates and intercalating fluorescent dyes to measure complementary DNA (cDNA) formation by reverse transcriptase in the presence of nucleotide reverse transcriptase inhibitor drugs. We optimized the RESTRICT assay using aqueous solutions of tenofovir diphosphate (TFV-DP), a metabolite that indicates long-term adherence to ART and PrEP, at concentrations over 2 orders of magnitude above and below the clinically relevant range. We used dilution in water as a simple sample preparation strategy to detect TFV-DP spiked into whole blood and accurately distinguished TFV-DP drug levels corresponding to low and high PrEP adherences. The RESTRICT assay is a fast and accessible test that could be useful for patients and clinicians to measure and improve ART and PrEP adherence.