Tobramycin Systemic Absorption in Lung Transplant Recipients Treated With Inhaled Tobramycin: A Cohort Study.

Inhaled tobramycin treatment has been associated with nephrotoxicity in some case reports, but limited data are available about serum levels and its possible systemic absorption in lung transplant recipients (LTR). We conducted a single-center, observational and retrospective study of all adult (>18 years old) LTR treated with inhaled tobramycin for at least 3 days between June 2019 and February 2022. Trough serum levels were collected and >2 µg/mL was considered a high drug level. The primary outcome assessed the presence of detectable trough levels, while the secondary outcome focused on the occurrence of acute kidney injury (AKI) in individuals with detectable trough levels. Thirty-four patients, with a median age of 60 years, were enrolled. The primary indications for treatment were donor bronchial aspirate bacterial isolation (18 patients) and tracheobronchitis (15 patients). In total, 28 patients (82%) exhibited detectable serum levels, with 9 (26%) presenting high levels (>2 µg/mL). Furthermore, 9 patients (26%) developed acute kidney injury during the treatment course. Median trough tobramycin levels were significantly elevated in invasively mechanically ventilated patients compared to non-ventilated individuals (2.5 µg/mL vs. 0.48 µg/mL) (p < 0.001). Inhaled tobramycin administration in LTRs, particularly in those requiring invasive mechanical ventilation, may result in substantial systemic absorption.

Non-trough serum drug levels of adalimumab and etanercept are associated with response in patients with psoriatic arthritis.

OBJECTIVES: Up to 40% of psoriatic arthritis (PsA) patients experience first-line Tumour Necrosis Factor inhibitors (TNF-i) failure. Lower serum drug levels (SDL) have been associated with lower response in autoimmune conditions. This study aimed to: (i) establish the relationship between adalimumab (ADL) and etanercept (ETN) SDL and 3-month response; and (ii) identify optimal non-trough SDL thresholds in PsA. METHODS: PsA patients commencing ADL or ETN were recruited to the UK observational study OUTPASS. Patients were seen pre-TNF-i and at 3 months when response was measured, and non-trough serum samples collected. Response was defined according to the PsARC or EULAR criteria. Descriptive statistics and concentration-effect curves established differences in SDL based on response. Receiver operating characteristics and regression identified optimal SDL thresholds. RESULTS: PsA ETN (n = 97) PsARC and EULAR good responders had significantly higher 3-month SDL compared with non-responders (p= 0.006 and p= 0.020 respectively). Non-trough 3-month ETN SDL discriminated PsARC responders from non-responders (AUC = 0.70), with a threshold of 1.8 µg/ml being 63% specific and 69% sensitive. EULAR good and non-/moderate responders were discriminated with an AUC of 0.65 with a threshold of 2.0 µg/ml being 57% specific and 69% sensitive. ADL prescribed (n = 104) EULAR good responders had significantly higher 3-month SDL (p= 0.049). Non-trough 3-month ADL SDL discriminated EULAR good and non-/moderate responders (AUC = 0.63) with a threshold of 3.6 µg/ml being 48% specific and 81% sensitive. CONCLUSION: Higher 3-month SDL were detected in responders. Interventions to optimise SDL may improve treatment response earlier. This study suggests 3-month SDL thresholds which may be useful in clinical practice to optimise treatment response.

Non-trough adalimumab and certolizumab drug levels associated with a therapeutic EULAR response in adherent patients with rheumatoid arthritis.

OBJECTIVES: Interventions aimed at increasing TNF-α inhibitor serum drug levels (SDLs) may improve treatment response; however, previous studies suggesting SDL cut-offs have not accounted for treatment adherence. The aim of this study was to establish the relationship between adalimumab/certolizumab SDLs and EULAR good vs non-/moderate response and to define SDL cut-offs associated with good response in fully adherent patients. METHODS: In a prospective observational study, 475 patients with RA were treated with certolizumab (n = 192) or adalimumab (n = 283). At baseline and 3, 6 and 12 months, patients had 28-joint DAS, self-reported treatment adherence and SDLs measured. Fully adherent patients were analysed as a subgroup. Follow-up data at 3, 6 and 12 months were analysed separately. Median SDLs were compared in good vs non-/moderate response patients and receiver operating characteristics (ROC) curves were used to establish cut-off SDLs. RESULTS: Fully adherent good responders had significantly higher median adalimumab/certolizumab SDLs compared with non-/moderate responders (P = 0.04 and P = 0.0005, respectively). ROC analysis reported 3 month non-trough adalimumab SDLs discriminated good vs non-/moderate response with an area under the curve (AUC) of 0.63 (95% CI 0.52, 0.75), with a cut-off of 7.5 mg/l being 39.1% specific and 80.9% sensitive. Similarly, 3 month non-trough certolizumab SDLs discriminated good vs non-/moderate response with an AUC of 0.65 (95% CI 0.51, 0.78), with a cut-off of 26.0 mg/l being 43.9% specific and 77.8% sensitive. CONCLUSION: In fully adherent patients, higher SDLs are detected in good responders, suggesting that interventions to improve SDLs, such as encouraging adherence, could improve treatment response. The 3 month non-trough SDL cut-offs of 7.5 mg/l for adalimumab and 26.0 mg/l for certolizumab may be useful in clinical practice.

Therapeutic drug monitoring in inflammatory bowel disease: implementation, utilization, and barriers in clinical practice in Scandinavia.

BACKGROUND AND AIMS: Therapeutic drug monitoring (TDM) may optimize biologic and thiopurine therapies in inflammatory bowel disease (IBD). The study aimed to investigate implementation and utilization of TDM in Scandinavia. METHODS: A web-based questionnaire on the use of TDM was distributed to Scandinavian gastroenterologists via the national societies. RESULTS: In total, 297 IBD physicians prescribing biologic therapies, equally distributed between community and university hospitals, were included (response rate 42%) (Norway 118 (40%), Denmark 86 (29%), Sweden 50 (17%), Finland 33 (11%), Iceland 10 (3%)). Overall, TDM was applied during biologic therapies by 87%, and for TNF-inhibitors >90%. Among the users, reactive and proactive TDM were utilized by 90% and 63%, respectively. Danish physicians were significantly less inclined to use TDM compared to other Scandinavian countries; (58% vs 98%); OR 0.03 [0.01-0.09], p < 0.001). Reactive TDM was commonly applied at primary (74%) and secondary (99%) treatment failure. Proactive TDM was used by 80% during maintenance therapy and 56% during induction and more commonly utilized in Norway (p < 0.001), and by physicians managing >10 IBD patients/week (p = 0.005). TDM scenarios were interpreted in accord with available evidence but with discrepancies for proactive TDM. The main barriers to TDM were lack of guidelines (51%) and time lag between sampling and results (49%). TDM of thiopurines was routinely used by 87%. CONCLUSION: TDM of biologic and thiopurine therapies has been broadly implemented into clinical practice in Scandinavia. However, physicians call for TDM guidelines detailing indications and interpretations of test results along with improved test response times.

Drug levels, anti-drug antibodies and B-cell counts were not predictive of response in rheumatoid arthritis patients on (ultra-)low-dose rituximab.

OBJECTIVES: The REDO trial (REtreatment with Rituximab in RhEumatoid arthritis: Disease Outcome after Dose Optimisation) showed that ultra-low-dose rituximab (500 mg or 200 mg) was similarly effective to a 1000 mg dosage in the majority of RA patients. This pre-planned secondary analysis investigated (1) associations between rituximab dosage, drug levels, anti-drug antibodies (ADAs) and B-cell counts and (2) the predictive value of pharmacokinetic and pharmacodynamic parameters, and of patient, disease and treatment characteristics in relation to response to ultra-low-dose rituximab. METHODS: For 140 RA patients from the REDO trial, differences in drug levels, ADAs and B-cell counts were examined at baseline, and at 3 and 6 months after dosing. Treatment response was defined as absence of flare and no extra rituximab or >1 glucocorticoid injection received during follow-up. The association between potential predictors and response was investigated using logistic regression analyses. RESULTS: Lower doses of rituximab resulted in lower drug levels but did not significantly affect ADA levels or B-cell counts, and 3 (10.7%), 12 (20.7%) and 7 (13.0%) patients failed to meet the response criteria in, respectively, the 1000 mg, 500 mg and 200 mg dosage groups. Drug levels, ADAs, B-cell counts, and patient, disease and treatment characteristics were not predictive for response to ultra-low-dose rituximab. CONCLUSION: The results of this study further support the hypothesis that continued treatment with 500 or 200 mg rituximab is similarly effective to a 1000 mg dosage in RA patients doing well on rituximab. These results, combined with lack of finding a clinical dose-response relationship in the original REDO study, suggest that 200 mg rituximab is not yet the lowest effective rituximab retreatment dose in RA.

Objective disease activity assessment and therapeutic drug monitoring prior to biologic therapy changes in routine inflammatory bowel disease clinical practice: TARGET-IBD.

BACKGROUND: Inflammatory bowel disease (IBD) treatment paradigms recommend objective disease activity assessment and reactive therapeutic drug monitoring (TDM) prior to changes in biologic therapy. We aimed to describe objective marker and TDM assessment in routine clinical practice prior to biologic therapeutic changes in adult IBD patients. METHODS: TARGET-IBD is a prospective longitudinal cohort of over 2100 IBD patients receiving usual care at 34 US academic or community centers enrolled between June 2017 and October 2019 who received biologic therapy and had a dose change or biologic discontinuation for lack of efficacy. Objective markers of disease activity within 12 weeks prior included fecal calprotectin, C-reactive protein (CRP), endoscopy, computed tomography (CT) and magnetic resonance imaging (MRI). TDM data for infliximab or adalimumab was obtained. RESULTS: 525 patients (71.4% Crohn's disease [CD], 28.6% ulcerative colitis [UC]) receiving biologic therapy underwent dose change (55.6%) or discontinuation (44.4%) for lack of efficacy. The majority were Caucasian (85.7%), 18-39 years old (52.2%), privately insured (81.5%), and at academic centers (73.7%). For dose changes, 67.5% had at least one objective disease activity assessment or TDM in the 12 weeks prior (CD 67.9%, UC 66.2%; P = 0.79). The most common objective marker was CRP in both CD (39.1%) and UC (54.5%). CRP and calprotectin were used significantly more in UC (P = 0.02 and P = 0.03). TDM was obtained in 30.7% (28.8% UC, 31.4% CD; P = 0.72) prior to dose change. For biologic discontinuation, 79.4% patients underwent objective assessment or TDM prior. In CD, CRP (46.3%) was most common, and CT (P = 0.03) and MRI (P < 0.001) were significantly more frequent than in UC. TDM was performed in 40.1% of patients (43.5% UC, 38.0% CD, P = 0.49) prior to discontinuation. Among all participants with dose change or discontinuation, endoscopy was performed in 29.3% with CD and 31.3% with UC. Academic care setting was associated with objective assessment before therapy change (OR 1.59, 95% CI 1.01-2.50). CONCLUSION: Nearly one-third of patients undergoing a biologic dose change or discontinuation do not undergo objective disease activity assessment or TDM. Assessment choice differs by disease. Future studies assessing the impact of such practices on long-term outcomes are needed.

LID study: Plasma lidocaine levels following airway topicalisation for paediatric microlaryngobronchoscopy (MLB).

OBJECTIVES: A dose of 5 mg/kg lidocaine is considered appropriate for paediatric airway topicalisation. Existing literature suggests that younger children are susceptible to toxic lidocaine plasma levels and achieve this at a faster rate. MAIN OUTCOME MEASURES: The primary outcome of this study was to ascertain peak plasma lidocaine levels after topicalisation for airway endoscopy. Secondary endpoints included: time to peak lidocaine plasma levels, signs of lidocaine toxicity (restricted to ECG changes or seizures when under anaesthesia) and clinical adverse events of laryngospasm, coughing or desaturation during the procedure. SETTING: Data were collected prospectively over 18 months at Royal Manchester Children's Hospital. PARTICIPANTS: Children aged 0-8 years undergoing elective diagnostic or therapeutic airway endoscopy were included within the study. DESIGN: Standardised 2% lidocaine was used for airway topicalisation. Dose varied depending upon the practitioner's usual practice. Venous bloodsampling occurred at 5, 10, 15 and 20 min post-administration and plasma lidocaine levels (ng/ml) were analysed. RESULTS: A significant relationship exists between higher peak plasma levels and ages <18 months (p = .00973). Strong linear correlation exists between body weight and age for our cohort (r = .88). Higher peak plasma lidocaine levels occur with total dose volumes between 2 and 3 mls of 2% lidocaine local anaesthetic (p = .03) compared with <2 ml total dose volumes. Data suggest a potential relationship of lower body weights achieving higher peak plasma levels (p = .0516). Reduced interquartile variation of peak plasma lidocaine levels exists when lidocaine dosing is <5 mg/kg. CONCLUSIONS: Age and total dose volume of topicalised lidocaine have a significant relationship with plasma lidocaine levels. A dose of 5 mg/kg topicalised lidocaine for paediatric airway endoscopy is safe and provides good operating conditions. Lower patient body weights trend towards higher peak lidocaine plasma concentrations and require further investigation.

Genital Shedding of Human Immunodeficiency Virus Type-1 (HIV) When Antiretroviral Therapy Suppresses HIV Replication in the Plasma.

BACKGROUND: During antiretroviral treatment (ART) with plasma HIV RNA below the limit of quantification, HIV RNA can be detected in genital or rectal secretions, termed discordant shedding (DS). We hypothesized that proliferating cells produce virions without HIV replication. METHODS: ART-naive Peruvians initiating ART were observed for DS over 2 years. HIV env and pol genomes were amplified from DS. Antiretrovirals and cytokines/chemokines concentrations were compared at DS and control time points. RESULTS: Eighty-two participants had ART suppression. DS was detected in 24/82 (29%) participants: 13/253 (5%) cervicovaginal lavages, 20/322 (6%) seminal plasmas, and 6/85 (7%) rectal secretions. HIV RNA in DS specimens was near the limit of quantification and not reproducible. HIV DNA was detected in 6/13 (46%) DS cervicovaginal lavages at low levels. Following DNase treatment, 5/39 DS specimens yielded HIV sequences, all without increased genetic distances. Women with and without DS had similar plasma antiretroviral levels and DS in 1 woman was associated with inflammation. CONCLUSIONS: HIV RNA and DNA sequences and therapeutic antiretroviral plasma levels did not support HIV replication as the cause of DS from the genital tract. Rather, our findings infer that HIV RNA is shed due to proliferation of infected cells with virion production.

Safe administration of high-dose methotrexate with minimal drug level monitoring: Experience from a center in north India.

BACKGROUND: High-dose methotrexate (HDMTX) is recommended to be administered with serial monitoring of methotrexate (MTX) levels, which may not be universally feasible in resource-limited settings. In this study, we evaluated the overall experience of administration of HDMTX at our center by monitoring a single drug level at 54 h from the start of MTX infusion. METHODS: This retrospective study was performed at a tertiary level hospital in north India, over a 5-year period (2011-2015). All patients <18 years of age with newly diagnosed acute lymphoblastic leukemia (ALL) and T-non-Hodgkin lymphoma (T-NHL) were enrolled in the study. Details of HDMTX and all significant toxicities requiring prolonged or repeat hospitalization were retrieved from the medical records. All eligible patients received HDMTX as per the recommendations followed by at least three doses of leucovorin rescue, before drug levels were sent at 54 h. Subsequent leucovorin doses were adjusted accordingly. RESULTS: The records of 598 cycles of HDMTX in 184 patients were reviewed. A total of 531 of 598 cycles (88.7%) were managed with monitoring only a single plasma drug level at 54 h from the beginning of infusion. Delayed MTX clearance was seen in 260 of 598 cycles (43.5%). Only three episodes (0.5%) were associated with significant toxicity. There were no deaths. CONCLUSIONS: The strategy of monitoring MTX concentration at 54 h was safe in our cohort. Although recommended, dynamic monitoring of plasma drug levels may not always predict toxicity.

Fluctuations in serum levels of adalimumab and infliximab in patients on stable treatment for psoriasis.

Many patients with psoriasis fail to respond to biologic drugs either initially or lose response over time, the latter having predominantly been linked to low circulating drug levels. We examined how serum drug levels varied over three treatment cycles of stable maintenance therapy with either adalimumab or infliximab among a total of 28 patients with psoriasis (22 men, mean age 48.6 years, mean treatment time 6.2 years) and whether there was an association with various patient-specific factors. The range for all concentrations was 1.1 to 24.3 µg/mL for adalimumab and 0.0 to 180.6 µg/mL for infliximab. There was a consistent inverse association between body mass index (BMI) and trough and maximum serum concentrations of adalimumab (P < .05 for all comparisons) and a positive, less consistent, association between age and maximum serum concentration of infliximab (P < .05 for both comparisons). Patient-specific factors, such as BMI and age, can help predict fluctuations in serum concentrations of biologics used for psoriasis.

Lessons learned from immunoadsorption for hyperviscosity in IgM multiple myeloma-A case report.

We report the case of a 63-year-old Caucasian woman with multiple relapsed IgM multiple myeloma (MM) and elevated free kappa light chains (fκLC). Due to hyperviscosity syndrome with visual impairment, regular plasma exchanges were performed. As part of her 11th line of therapy, an experimental protocol consisting of pembrolizumab, pomalidomide, and dexamethasone was initiated. To reduce fκLC and immunoglobulin (Ig) M, we performed immunoadsorption (IA) using columns containing recombinant single domain camelid antibody fragments as ligands. We measured pembrolizumab (humanized IgG4 kappa anti-PD1 antibody) levels before and after each IA session and found a 98.1% reduction from baseline with five sessions of IA. Comparable elimination kinetics were observed for serum IgG, whereas fκLC and IgM were eliminated to a substantially lesser extent. These findings highlight that in hyperviscosity syndrome due to IgM MM, broad spectrum IA columns might be only moderately effective compared to total plasma exchange or double filtration plasmapheresis. Monoclonal antibodies are efficiently reduced by extracorporeal therapies and re-dosing is necessary to provide sufficient efficacy. In the case of serious adverse events such as immune-related adverse events, IA might be used to eliminate the monoclonal antibody. Measuring IgG levels might be a reasonable strategy for monitoring drug levels of monoclonal antibodies during IA.

Does determination of drug level in intoxicated patients offer an advantage in diagnosis, treatment, and reducing complications?

OBJECTIVE: To investigate the effect of determining the drug type and level on emergency management in patients presenting with intoxication, and to identify the factors behind associated mortality. METHODS: The retrospective, observational, cross-sectional and single centre study was conducted at a large tertiary care teaching hospital in Istanbul, Turkey, between September and November 2016 using the hospital's toxicology registry. Data was extracted for patients who had presented to the emergency department from January 1, 2011, to February 28, 2013, and were found to have toxic doses of single active ingredients in the plasma. The patients were evaluated in terms of age, gender, demographic characteristics, time from ingestion to presentation, reason for drug ingestion, type of drug ingested, time elapsed before the emergency service was called, treatment given, drug level, hospitalisation and mortality. Data was analysed using SPSS 11.5. RESULTS: Of the 224 patients, 145(64.8%) were women. The overall mean age was 30.8±15.4 years. Drug ingestion was more common in women aged 18-30 years (p<0.0001). Besides, 215(96%) patients had ingested drugs with the intent to commit suicide. The minimum education level of 163(72.8%) patients was high school. The most frequently ingested drug was paracetamol 90(40.2%). Overall mortality was 4(1.8%) and all of them were brought to the emergency department after a delay of more than five hours (p<0.0001). CONCLUSIONS: Drug type and quantity were found to be of great importance in taking timely decisions while attending to patients with intoxication in an emergency setting. Delay in presentation was associated with mortality..

Low Central Nervous System Posaconazole Concentrations during Cerebral Phaeohyphomycosis.

Posaconazole diffusion has been documented in various organs, which contrasts with the scarce data available for the human central nervous system (CNS). We analyzed posaconazole concentrations in plasma and multiple CNS specimens taken from a patient who received posaconazole because of cerebral phaeohyphomycosis. Low posaconazole concentrations were obtained in CNS specimens, with sample-to-plasma ratios between 5% and 22%. This case highlights the role of neurosurgery during cerebral phaeohyphomycoses, even those caused by posaconazole-susceptible black fungi.

Adalimumab drug and antidrug antibody levels do not predict flare risk after stopping adalimumab in RA patients with low disease activity.

OBJECTIVE: To establish whether serum adalimumab (ADA) trough level (ADA-TL) and antidrug antibody (ADA-ab) level predict flare after stopping ADA in established RA patients with long-standing low disease activity. METHODS: From the clinical trial Potential Optimalisation and Effectiveness of TNF-blockers, 210 RA patients stopping ADA, who had been using ADA (40 mg/2 weeks) for >1 year with conventional synthetic DMARDs and who had low disease activity (DAS28 < 3.2, or the rheumatologist's assessment of low disease activity with CRP < 10 mg/l) for at least 6 months prior to stopping, were followed for 1 year. The ADA-TL was measured (by ELISA) 12-17 days after the last ADA injection; if it was low, ADA-abs were measured (by an antigen-binding test). Association between time-to-flare and ADA-TL was evaluated by area under the receiver operating characteristic curve and Cox regression. RESULTS: A total of 106 (51%) patients flared within 1 year after stopping ADA. The area under the receiver operating characteristic curve for flare and ADA-TL was 0.50 (95% CI 0.42-0.58), P = 0.92. The hazard ratio for flare for ADA-TL ⩾ 5 µg/ml (adequate level) vs <5 µg/ml was 0.93 (95% CI: 0.63-1.36) (not significant). Of the 4 patients with high ADA-ab levels, 2 patients (50%) experienced a flare. CONCLUSION: Flare risk within the year following stopping ADA is not predicted by the ADA-TL or ADA-abs assessed at the moment of stopping. TRIAL REGISTRATION: Netherlands Trial Register, http://www.trialregister.nl, NTR3112.

Appropriateness of direct oral anticoagulant dosing and its relation to drug levels in atrial fibrillation patients.

Direct oral anticoagulants (DOACs) are commonly administered at a level that is lower than that recommended by dose reduction criteria. This raises concern regarding the adequacy of anticoagulation achieved. To evaluate the relationship between inappropriate dosing and DOAC levels. Medical records of atrial fibrillation patients who underwent DOAC level testing during 2013-2017 were reviewed. The primary outcomes were drug levels under and above the expected steady-state range, and in the lowest and highest quartiles. Of 143 patients who underwent DOAC measurements, only 87 (60.8%) received the appropriate dose. Levels under the expected range and in the lowest quartile were found in 11.9% and 15.0% of patients treated with appropriate dosing compared to 21% and 41.5% of patients treated with inappropriately low dose. DOAC levels were above the expected range and in the highest quartile in 23.8% and 32.5% of patients treated with the appropriate dose compared to 7.1% and 9.4% treated with inappropriately low dose. In multivariate analysis, the administration of an appropriate DOAC dose was associated with a lower rate of DOAC in the lowest level (adjusted odds ratio [95% CI] 0.30 (0.12, 0.76), P = 0.011). On the other hand, appropriate dose was associated with drug levels in the highest quartile (odds ratio [95% CI] 3.77 (0.12, 0.76), P = 0.011). Treatment with inappropriately low DOAC dosing compared to appropriate dose is associated with lower DOAC levels. However, among those treated with appropriate dosing, a higher proportion had high DOAC levels above the expected range.

Adherence Measurements in HIV: New Advancements in Pharmacologic Methods and Real-Time Monitoring.

PURPOSE OF REVIEW: In this review, we present new developments in antiretroviral adherence, focusing on pharmacological measures and real-time adherence monitoring. In addition, new strategies on how to incorporate these new measures into research and clinical care are proposed. RECENT FINDINGS: Antiretroviral drug concentrations in hair and dried blood spots are two novel pharmacological measures of cumulative drug adherence and exposure that have been recently evaluated in HIV treatment and pre-exposure prophylaxis. Real-time adherence monitoring using electronic devices has also proven highly informative, feasible, and well accepted, offering the possibility for an immediate intervention when non-adherence is detected. Both approaches offer considerable advantages over traditional adherence measures in predicting efficacy. New methods to objectively monitor adherence in real-time and over long time periods have been developed. Further research is required to better understand how these measures can optimize adherence and, ultimately, improve clinical outcomes in HIV treatment and prevention.

Direct-acting oral anticoagulant drug level monitoring in clinical patient management.

The role of drug-level monitoring among patients using direct-acting oral anticoagulant (DOAC) is unclear. We aimed to investigate its 'real-life' utilization and effect on clinical management. A review of records of patients who underwent DOAC level testing during 2013-2017. Overall, 212 patients (median age 77 years) underwent 292 DOAC measurements [apixaban (n = 147), rivaroxaban (n = 102), dabigatran (n = 43)]. Monitoring volume increased by 460% during study period. DOAC level testing was performed during routine follow-up in 51 (17.5%) cases, whereas the remaining 241 (82.5%) measurements were performed due to selected clinical circumstances, most commonly: bleeding (n = 60), perioperative status (n = 45), breakthrough thrombosis (n = 37) and renal failure (n = 35). Drug levels were within the expected range in 210 (71.9%), above the expected range in 62 (21.2%) and lower than expected range in 20 (6.8%). In multivariate analysis, older age (P = 0.005), lower glomerular filtration rate (P = 0.001) and lower body mass index (P = 0.006) were associated with DOAC levels above the expected range. Clinical decisions were affected by DOAC monitoring following most (140/241, 58.1%) measurements for which we identified an indication for testing; yet only rarely when monitoring was performed during routine follow-up (7.8%, 4/51) (P < 0.0001). While no benefit of routine DOAC monitoring was observed, drug level measurement has an important role in the management of patients in selected circumstances. Age, body weight and creatinine clearance were found to be significant predictors of drug levels. Future studies are warranted to establish associations between drug levels and outcomes, and better delineate the role of DOAC monitoring.

Drug interaction as a predictor of direct oral anticoagulant drug levels in atrial fibrillation patients.

Data are limited on the effects of drug interactions on direct-acting oral anticoagulant (DOAC) levels. We evaluated the effects of the use of interacting drugs on DOAC levels in patients with atrial fibrillation (AF). We reviewed data of AF patients tested for DOAC levels in 2013-2017. The primary outcomes were drug levels exceeding the expected steady-state range, and in the highest quartile. A multivariate analysis was performed to evaluate the correlation of treatment by the use of interacting drugs, CYP3A4 and P-glycoprotein (P-gp) inhibitors, with the primary outcomes. Overall, 147 patients underwent DOAC level measurement [dabigatran (n = 31), rivaroxaban (n = 29), apixaban (n = 87)]. Thirty-three (22.4%) had drug levels exceeding the expected range. Seventy-nine (53.7%) patients were treated with at least one interacting drug. In multivariate analysis, the concomitant use of interacting drugs was an independent predictor for drug levels exceeding the expected range (OR 3.3, 95% CI 1.20-9.05). The defined daily dose of the interacting drug correlated positively with DOAC levels (r = 0.29, P = 0.001). Co-treatment with interacting drugs was associated with extremely high levels of dabigatran, (OR 16.6, 95% CI 1.29-215.18) but not of the other DOAC examined. Concomitant use of interacting drugs is associated with high DOAC levels in patients with AF. Further investigation is warranted to establish the differences between specific DOAC, evaluate the effect on patient outcomes, and characterize the role of DOAC monitoring in this setting.

Serum drug levels of biologic agents in the management of rheumatoid arthritis and spondyloarthritis: a systematic review.

The utility of monitoring drug levels in rheumatoid arthritis and spondyloarthritis patients on biological therapy is called into question. The objective was to study relevant clinical questions on the topic, i.e., (1) whether drug levels predict relapse in patients whose biologic was optimized because of remission or low disease activity; (2) whether information about drug levels influences the prognosis of patients with primary or secondary failure to a biological therapy; and (3) whether methotrexate (MTX) influences the association between drug levels and response. Medline, Embase, Cochrane databases were screened, from inception to December 2016 in search for all studies related to the three research questions about. Overall characteristics and outcomes of the studies were collected in a table of evidence and the quality of the studies was assessed with the Newcastle-Ottawa scale or the GRADEpro. Two studies responded the first question, 5 the second, and 7 the third. Studies were small and with limitations, but suggest that measurement drug levels may be useful in patients in remission; that higher drug levels predict a longer relapse-free optimization, and in patients with failure to a biological agent, treatment may need individual adjustment according to the presence of drug levels or antidrug-antibodies. In addition, MTX influences the association between response and drug levels. Monitoring drug levels would allow optimal use of current biological therapies, but more studies and of better quality are needed to draw definitive conclusions.

Evaluation of Posaconazole Serum Concentrations from Delayed-Release Tablets in Patients at High Risk for Fungal Infections.

The purpose of our study was to determine the frequency of patients who achieved a therapeutic drug level after receiving posaconazole (PCZ) delayed-release tablets (DRT) for prophylaxis or treatment of invasive fungal infections (IFIs) and to examine the effect of demographic traits and treatment characteristics on PCZ serum levels. A retrospective single-center study was conducted on high-risk inpatients at the University of Washington Medical Center (UWMC) that had received PCZ and obtained PCZ serum levels for either treatment or prophylaxis between 1 August 2014 and 31 August 2015. High-risk patients were defined as those undergoing chemotherapy for a primary hematologic malignancy and those undergoing hematopoietic cell transplantation (HCT) or solid organ transplantation. Serum trough concentrations of ≥700 µg/liter and ≥1,000 µg/liter were considered appropriate for prophylaxis and treatment, respectively. The most frequent underlying medical condition was a hematological malignancy (43/53, 81%). Twenty-six of 53 patients (49%) received PCZ for prophylaxis; the rest received PCZ for treatment. A total of 37/53 (70%) patients had PCZ serum levels of ≥700 µg/liter regardless of indication, including 22/26 (85%) that received PCZ for prophylaxis. Of the patients that received PCZ for treatment, only 12/27 (44%) had PCZ serum levels of ≥1,000 µg/liter. The odds of having therapeutic PCZ serum levels were not statistically different in patients with a weight of ≥90 kg, a diarrhea grade of ≥2, a mucositis grade of ≥2, or poor dietary intake. However, the odds of having therapeutic PCZ serum levels was 5.85 times higher in patients without graft-versus-host disease (GVHD) treatment than in those with GVHD treatment. Four patients on prophylaxis (15%) developed breakthrough IFIs, one of which had a subtherapeutic level. We concluded that the use of PCZ DRT provided adequate concentrations in only 70% of our patients and that recommended dosing may lead to insufficient levels in patients treated for IFIs. Lower concentrations noted among high-risk patients with GVHD suggest a need for prospective studies evaluating therapeutic drug monitoring and/or dose adjustments among these patients.