Markus Hovd

• Eide, Per Kristian; Sherwani, Alexander Gul; Romundstad, Luis; Fjeld, Jan Gunnar; Eriksson, Amanda & Hjørnevik, Trine [Show all 7 contributors for this article] (2026). Ventricular CSF-to-blood water transport kinetics in adult hydrocephalus. Journal of Cerebral Blood Flow and Metabolism. ISSN 0271-678X. doi: 10.1177/0271678X261466792. Full text in Research Archive
• Eide, Per Kristian; Lashkarivand, Aslan; Hernes, Susanne Miriam Sørensen; Ringstad, Geir Andre & Hovd, Markus (2026). Estimation of human brain fluid clearance using intrathecal imaging contrast agents. Fluids and Barriers of the CNS. 23(1). doi: 10.1186/s12987-026-00826-1. Full text in Research Archive Show summary

  Background Extra-vascular brain fluid dynamics, including exchange through glymphatic and meningeal lymphatic pathways, has been proposed essential for waste clearance and solute transport in the central nervous system. Although animal studies provide evidence for these pathways’ role in clearing neurotoxic proteins and distributing solutes delivered to cerebrospinal fluid (CSF), translation to humans is limited. Quantitative, in vivo measures of inter-individual variability in brain fluid clearance in clinical populations are largely lacking. This study investigated the feasibility of estimating brain fluid clearance indices using intrathecal imaging contrast agents. Methods In a prospective and observational study, iodixanol (Visipaque, GE Healthcare, USA, 270 mg I/mL, 3 mL) was administered intrathecally as a CSF tracer and its clearance from CSF to blood was quantified using population pharmacokinetic modeling. Intracranial tracer enrichment in CSF was assessed by its radiodensity (Hounsfield units) within predefined regions of interest (cisterna magna, Sylvian fissure and vertex) on cranial computed tomography (CT) performed 2-, 4- and 24-hours post-injection. These results were compared with brain fluid clearance indices derived from a separate population pharmacokinetic model using intrathecal gadobutrol (Gadovist, Bayer AG, GE, 1.0 mmol/mL, 0.50 mL), with its enrichment in CSF defined as gadobutrol-induced T1 signal increase from baseline within corresponding subarachnoid spaces on magnetic resonance imaging (MRI). Results The study included 52 subjects receiving intrathecal iodixanol and 45 individuals receiving intrathecal gadobutrol. Marked inter-individual variability was observed in brain fluid clearance to blood for both contrast agents, as well as their distribution in CSF as assessed by CT and MRI. Brain fluid clearance from iodixanol and gadobutrol were significantly correlated. Notably, clearance indices showed stronger correlations with intracranial distribution in CSF for gadobutrol-derived MRI metrics than for iodixanol-derived CT metrics. Conclusions These findings demonstrate the feasibility of estimating brain fluid clearance in humans using intrathecal imaging contrast agents as CSF tracers. Brain fluid clearance capacity exhibits pronounced inter-individual variability and correlates with the degree of contrast enrichment in intracranial subarachnoid spaces, particularly when assessed by MRI. The results underscore the importance of individualized assessment of brain fluid clearance, with implications for studies on pathogenetic mechanisms of neurodegeneration and optimization of intrathecal drug delivery.

• Eide, Per Kristian; Hovd, Markus; Valnes, Lars Magnus; Pripp, Are Hugo & Ringstad, Geir Andre (2026). When blood hits the brain: altered glymphatic and dural lymphatic function after surface bleeds. Acta Neurochirurgica. ISSN 0001-6268. 168. doi: 10.1007/s00701-025-06760-9. Full text in Research Archive Show summary

  Background The impact of acute subdural hematoma (aSDH) on measures of glymphatic–meningeal lymphatic function has not previously been reported. We present a descriptive observational study including a small case series—one patient following unilateral aSDH, three following unilateral subarachnoid hemorrhage (SAH), and three control subjects—providing new insights into the differential effects of surface intracranial bleeds. Methods The magnetic resonance imaging (MRI) contrast agent gadobutrol (0.5 mmol), administered intrathecally, was used as a cerebrospinal fluid (CSF) tracer. Multiphase contrast-enhanced MRI was performed to assess glymphatic tracer enrichment. CSF tracer clearance to blood, serving as a proxy for dural lymphatic function, was estimated using population pharmacokinetic modeling. All hemorrhagic cases involved unilateral bleeds, allowing within-subject comparison between affected and unaffected hemispheres. Results The series included one patient with aSDH (2.8 months post-event), three patients with unilateral SAH (mean 5.8 months post-event), and three age-matched, near-healthy reference subjects. Compared with controls, glymphatic tracer enrichment 24 h post-injection was slightly increased on the affected hemisphere in the aSDH case, whereas SAH patients showed markedly reduced enrichment on the affected side. Tracer distribution in controls was symmetrical. CSF clearance to blood was notably reduced in the aSDH case compared with references, suggesting impaired dural lymphatic function. Conclusion This small descriptive series suggests that aSDH and SAH may differentially affect glymphatic and dural lymphatic functions. While glymphatic enrichment appeared only modestly altered after aSDH, it was severely impaired following SAH. In contrast, CSF clearance to blood was markedly reduced in the aSDH case, potentially reflecting compromised dural lymphatic drainage. The limited number of cases prevent broad generalization, but these findings offer novel hypothesis-generating observations that may inform future studies on the effects of surface intracranial hemorrhages on brain clearance pathways.

• Macente, Julia; Nauwelaerts, Nina; Badée, Justine Marine; Bonan, Rodolfo Hernandes; Huang, Miao Chan & Neste, Martje Van [Show all 12 contributors for this article] (2025). Predicting Drug Transfer Into Human Milk With the Simcyp Simulator: A Contribution From the ConcePTION Project. CPT: Pharmacometrics and Systems Pharmacology (PSP). 14(9), p. 1470–1484. doi: 10.1002/psp4.70066. Full text in Research Archive
• Sagedal, Solbjørg; Hovd, Markus; Åsberg, Anders; Mollnes, Tom Eirik; Klingenberg, Olav Inge & Heldal, Torbjørn Fossum [Show all 10 contributors for this article] (2025). Increased levels of ficolin-1 and of C3dg are independently associated with high risk of infection in patients with chronic kidney disease: a prospective cohort study. Frontiers in Immunology. 16. doi: 10.3389/fimmu.2025.1645347. Full text in Research Archive Show summary

  Background and hypothesis: Infection is a leading cause of morbidity and mortality in patients with chronic kidney disease (CKD). The complement system provides crucial first-line defense against pathogens. Mannose-binding lectin (MBL), ficolins (1, 2 and 3), and collectin-LK 1 (CL-LK) are pattern recognition molecules (PRMs) of the lectin pathway (LP) that recognize microbial surfaces and activate complement. C3dg is a complement cleavage fragment indicating complement activation. The aim of the study was to investigate whether levels of PRMs and C3dg are associated with the risk of significant infections requiring hospitalization in patients with CKD. Methods: This prospective cohort study included 518 patients ≥18 years with CKD (eGFR<60 mL/min/1.73 m2), consecutively recruited between 2008-2022. About half (270/518) were in dialysis at inclusion. None of the patients were previously transplanted with any organ or stem cells. The primary endpoint was non-access-related infections requiring hospitalization. Patients were followed until kidney transplantation or death or until 31.12.2024. Plasma concentrations of the biomarkers were measured at inclusion. Time-to-event analyses using Cox regression were employed to assess associations with infection, adjusting for age, sex, diabetes, dialysis status, and dialysis vintage. Results: During a median (interquartile range [IQR]) time of follow-up of 1.24 (0.49-2.76) years, 182 patients (35%) were hospitalized due to non-access infection. Higher baseline levels of ficolin-1 and C3dg were independently associated with infection risk, HR 3.05, 95% CI 1.25-7.43, p=0.01 and HR 2.97, 95% CI 1.37-6.44, p=0.006, respectively, for each log10 unit increase. In multivariable models including all biomarkers, only C3dg remained independently associated with infection (HR 2.81, 95% CI 1.23-6.43, p=0.01). Conclusions: High levels of complement activation (C3dg) and ficolin-1 were independently associated with increased infection risk in patients with CKD. A dysregulated complement activation rather than PRM deficiency seems to be a key pathogenic mechanism resulting in increased infection risk in advanced CKD.

• Eide, Per Kristian; Hovd, Markus; Pripp, Are Hugo; Gjertsen, Øivind; Løvland, Grethe & Lashkarivand, Aslan [Show all 9 contributors for this article] (2025). Altered brain fluid dynamics in spontaneous intracranial hypotension. Fluids and Barriers of the CNS. 22. doi: 10.1186/s12987-025-00679-0. Full text in Research Archive Show summary

  Background This prospective observational study explored alterations in brain fluid dynamics in patients with spontaneous intracranial hypotension (SIH) and confirmed spinal cerebrospinal fluid (CSF) leakage, specifically addressing CSF clearance to blood, glymphatic influx and measures of CSF flow. Methods A cohort of SIH patients with verified spinal CSF leaks was compared with an age- and sex-matched reference group having no CSF disturbance or neurological disorders. Prior to repair of CSF leakage, CSF clearance was quantified using population pharmacokinetics, glymphatic influx was assessed by intrathecal contrast-enhanced magnetic resonance imaging (MRI), and CSF flow patterns were measured using either phase-contrast MRI or multiphase analysis of CSF tracer transport within the subarachnoid spaces. Results The study included eight SIH cases and nine reference subjects. SIH was accompanied with a greater CSF clearance, severely reduced tracer enrichment in the subarachnoid spaces and impaired glymphatic influx throughout the brain, after the patients had been upright. However, with patients in the supine position during MRI scanning, times to first enrichment of tracer in cisterna magna or perivascular subarachnoid spaces were not affected, with no changes in CSF flow through the Sylvian aqueduct, indicating that ventricular CSF production remained unaffected. Conclusions SIH caused by spinal CSF leakage is accompanied with altered brain fluid dynamics, here illustrated by accelerated CSF clearance to blood and reduced glymphatic influx, likely due to reduced CSF volume load to the intracranial compartment in the upright position.

• Melander, Erik; Nielsen, Elisabet I.; Lindqvist, Annika; Hovd, Markus; Gandia, Peggy & Panchaud, Alice [Show all 11 contributors for this article] (2024). Population pharmacokinetic modelling of cetirizine concentrations in human breast milk—A contribution from the ConcePTION project. Basic & Clinical Pharmacology & Toxicology. ISSN 1742-7835. 136(1). doi: 10.1111/bcpt.14100. Full text in Research Archive
• Strømmen, Ruth Cecilie; Godang, Kristin; Hovd, Markus; Finnes, Trine Elisabeth; Smerud, Knut Terje & Hartmann, Anders [Show all 9 contributors for this article] (2024). Hip geometry and strength remain stable the first year after kidney transplantation—an ibandronate/placebo post hoc analysis. Journal of Bone and Mineral Research. ISSN 0884-0431. 8(12). doi: 10.1093/jbmrpl/ziae130. Full text in Research Archive Show summary

  The sensitivity of bone mineral density (BMD) to identify patients with high fracture risk after kidney transplantation is low, therefore alternative tools are needed. Hip Structure Analysis (HSA) provides an estimation of hip structural geometry and strength based on conventional DXA scans for hip analyses. We aimed to investigate the effect of antiresorptive therapy on hip geometrical and strength parameters by HSA. In a post hoc analysis of a 12-month randomized, double-blind, placebo-controlled trial evaluating the effect of ibandronate in addition to active vitamin D and calcium in kidney transplant recipients (KTR), we re-analyzed dual total hip and femoral neck DXA scans to measure cortical bone thickness (CBT) in the femoral neck (CBTNECK), calcar (CBTCALCAR), and shaft (CBTSHAFT), along with femur neck width, hip axis length, and to estimate buckling ratio and strength index. DXA measurements were performed within 5 weeks after transplantation and repeated at 10 weeks and 1-year post-transplant. The study included a total of 127 de novo KTR with estimated glomerular filtration rate >30 mL/min at baseline. The 5 geometrical and the strength and stability hip parameters remained stable over the first post-transplant year irrespective of antiresorptive therapy. We detected no statistically significant between-group differences in any of the HSA measures. Change in geometrical hip parameters and buckling ratio over the study duration was not correlated with change in plasma parathyroid hormone or change in dual total hip BMD. In this study, the so far largest of HSA in KTR, antiresorptive therapy with ibandronate for 12 months did not affect measures of hip geometry or strength.

• Kvitne, Kine Eide; Hjelmesæth, Jøran Sture; Hovd, Markus; Sandbu, Rune; Johnson, Line Kristin & Andersson, Shalini [Show all 11 contributors for this article] (2024). Oral Drug Dosing After Gastric Bypass and Diet-Induced Weight Loss: Simpler Than We Think? Lessons Learned From the COCKTAIL Study. Clinical Pharmacology and Therapeutics. ISSN 0009-9236. 16(3), p. 647–652. doi: 10.1002/cpt.3307. Full text in Research Archive Show summary

  This article summarizes the lessons learned from the COCKTAIL study: an open, three-armed, single-center study including patients with obesity scheduled for treatment with Roux-en-Y gastric bypass (RYGB) or nonsurgical calorie restriction, and a normal- to overweight control group. The clinical implications of the results from multiple peer-reviewed articles describing the effects of RYGB, severe caloric restriction, weight loss, and type 2 diabetes on the in vivo activity and protein expression of drug-metabolizing enzymes (cytochrome P450 (CYP) 1A2, 2C9, 2C19, and 3A) and transporters (DMETs; organic anion-transporting polypeptide (OATP) 1B1 and P-glycoprotein (P-gp)) are discussed in the perspective of three clinically relevant questions: (1) How should clinicians get the dose right in patients after RYGB? (2) Will drug disposition in patients with obesity be normalized after successful weight loss? (3) Are dose adjustments needed according to obesity and diabetes status? Overall, RYGB seems to have a lower impact on drug disposition than previously assumed, but clinicians should pay close attention to drugs with a narrow therapeutic range or where a high maximum drug concentration may be problematic. Whether obesity-related alterations of DMETs normalize with substantial weight loss depends on the DMET in question. Obesity and diabetes downregulate the in vivo activity of CYP2C19 and CYP3A (only obesity) but whether substrate drugs should be dose adjusted is also dependent on other factors that influence clearance, that is, liver blood flow and protein binding. Finally, we recommend frequent and individualized follow-up due to high inter- and intraindividual variability in these patients, particularly following RYGB.

• Eide, Per Kristian; Lashkarivand, Aslan; Pripp, Are Hugo; Valnes, Lars Magnus; Hovd, Markus Herberg & Ringstad, Geir [Show all 8 contributors for this article] (2023). Plasma neurodegeneration biomarker concentrations associate with glymphatic and meningeal lymphatic measures in neurological disorders. Nature Communications. 14, p. 1–14. doi: 10.1038/s41467-023-37685-5. Full text in Research Archive Show summary

  Clearance of neurotoxic brain proteins via cerebrospinal fluid (CSF) to blood has recently emerged to be crucial, and plasma biomarkers of neurodegen- eration were newly introduced to predict neurological disease. This study examines in 106 individuals with neurological disorders associations between plasma biomarkers [40 and 42 amino acid-long amyloid-β (Aβ40 and Aβ42), total-tau, glial fibrillary acidic protein (GFAP), and neurofilament light (NfL)] and magnetic resonance imaging measures of CSF-mediated clearance from brain via extra-vascular pathways (proxy of glymphatic function) and CSF-to- blood clearance variables from pharmacokinetic modeling (proxy of menin- geal lymphatic egress). We also examine how biomarkers vary during daytime and associate with subjective sleep quality. Plasma concentrations of neuro- degeneration markers associate with indices of glymphatic and meningeal lymphatic functions in individual- and disease-specific manners, vary during daytime, but are unaffected by sleep quality. The results suggest that plasma concentrations of neurodegeneration biomarkers associate with measures of glymphatic and meningeal lymphatic function.

• Hovd, Markus Herberg; Robertsen, Ida; Woillard, Jean-Baptiste & Åsberg, Anders (2023). A Method for Evaluating Robustness of Limited Sampling Strategies—Exemplified by Serum Iohexol Clearance for Determination of Measured Glomerular Filtration Rate. Pharmaceutics. 15(4). doi: 10.3390/pharmaceutics15041073. Full text in Research Archive Show summary

  In combination with Bayesian estimates based on a population pharmacokinetic model, limited sampling strategies (LSS) may reduce the number of samples required for individual pharmacokinetic parameter estimations. Such strategies reduce the burden when assessing the area under the concentration versus time curves (AUC) in therapeutic drug monitoring. However, it is not uncommon for the actual sample time to deviate from the optimal one. In this work, we evaluate the robustness of parameter estimations to such deviations in an LSS. A previously developed 4-point LSS for estimation of serum iohexol clearance (i.e., dose/AUC) was used to exemplify the effect of sample time deviations. Two parallel strategies were used: (a) shifting the exact sampling time by an empirical amount of time for each of the four individual sample points, and (b) introducing a random error across all sample points. The investigated iohexol LSS appeared robust to deviations from optimal sample times, both across individual and multiple sample points. The proportion of individuals with a relative error greater than 15% (P15) was 5.3% in the reference run with optimally timed sampling, which increased to a maximum of 8.3% following the introduction of random error in sample time across all four time points. We propose to apply the present method for the validation of LSS developed for clinical use.

• Kared, Hassen; Alirezaylavasani, Amin; Lund, Kathrine Persgård; Chopra, Adity; Tietze, Lisa & Kasahara, Taissa de Matos [Show all 17 contributors for this article] (2023). Hybrid and SARS-CoV-2-vaccine immunity in kidney transplant recipients. EBioMedicine. 97. doi: 10.1016/j.ebiom.2023.104833. Full text in Research Archive Show summary

  Background Kidney transplant recipients (KTR) are at high risk for severe COVID-19 and have demonstrated poor response to vaccination, making it unclear whether successive vaccinations offer immunity and protection. Methods We conducted a serologically guided interventional study where KTR patients that failed to seroconvert were revaccinated and also monitored seroconversion of KTR following the Norwegian vaccination program. We analysed IgG anti-RBD Spike responses from dose 2 (n = 432) up to after the 6th (n = 37) mRNA vaccine dose. The frequency and phenotype of Spike-specific T and B cell responses were assessed in the interventional cohort after 3–4 vaccine doses (n = 30). Additionally, we evaluated the Specific T and B cell response to breakthrough infection (n = 32), measured inflammatory cytokines and broadly cross-neutralizing antibodies, and defined the incidence of COVID-19-related hospitalizations and deaths. The Norwegian KTR cohort has a male dominance (2323 males, 1297 females), PBMC were collected from 114 male and 78 female donors. Findings After vaccine dose 3, most KTR developed Spike-specific T cell responses but had significantly reduced Spike-binding B cells and few memory cells. The B cell response included a cross-reactive subset that could bind Omicron VOC, which expanded after breakthrough infection (BTI) and gave rise to a memory IgG+ B cell response. After BTI, KTR had increased Spike-specific T cells, emergent non-Spike T and B cell responses, and a systemic inflammatory signature. Late seroconversion occurred after doses 5–6, but 38% (14/37) of KTR had no detectable immunity even after multiple vaccine doses. Interpretation Boosting vaccination can induce Spike-specific immunity that may expand in breakthrough infections highlighting the benefit of vaccination to protect this vulnerable population.

• Eide, Per Kristian; Lashkarivand, Aslan; Pripp, Are Hugo; Valnes, Lars Magnus; Hovd, Markus & Ringstad, Geir [Show all 8 contributors for this article] (2023). Mechanisms behind changes of neurodegeneration biomarkers in plasma induced by sleep deprivation. Brain Communications. 5(6). doi: 10.1093/braincomms/fcad343. Full text in Research Archive Show summary

  Acute sleep deprivation has been shown to affect cerebrospinal fluid and plasma concentrations of biomarkers associated with neurodegeneration, though the mechanistic underpinnings remain unknown. This study compared individuals who, for one night, were either subject to total sleep deprivation or free sleep, (i) examining plasma concentrations of neurodegeneration biomarkers the morning after sleep deprivation or free sleep and (ii) determining how overnight changes in biomarkers plasma concentrations correlate with indices of meningeal lymphatic and glymphatic clearance functions. Plasma concentrations of amyloid-β 40 and 42, phosphorylated tau peptide 181, glial fibrillary acid protein and neurofilament light were measured longitudinally in subjects who from Day 1 to Day 2 either underwent total sleep deprivation (n = 7) or were allowed free sleep (n = 21). The magnetic resonance imaging contrast agent gadobutrol was injected intrathecally, serving as a cerebrospinal fluid tracer. Population pharmacokinetic model parameters of gadobutrol cerebrospinal fluid-to-blood clearance were utilized as a proxy of meningeal lymphatic clearance capacity and intrathecal contrast-enhanced magnetic resonance imaging as a proxy of glymphatic function. After one night of acute sleep deprivation, the plasma concentrations of amyloid-β 40 and 42 were reduced, but not the ratio, and concentrations of the other biomarkers were unchanged. The overnight change in amyloid-β 40 and 42 plasma concentrations in the sleep group correlated significantly with indices of meningeal lymphatic clearance capacity, while this was not seen for the other neurodegeneration biomarkers. However, overnight change in plasma concentrations of amyloid-β 40 and 42 did not correlate with the glymphatic marker. On the other hand, the overnight change in plasma concentration of phosphorylated tau peptide 181 correlated significantly with the marker of glymphatic function in the sleep deprivation group but not in the sleep group. The present data add to the evidence of the role of sleep and sleep deprivation on plasma neurodegeneration concentrations; however, the various neurodegeneration biomarkers respond differently with different mechanisms behind sleep-induced alterations in amyloid-β and tau plasma concentrations. Clearance capacity of meningeal lymphatics seems more important for sleep-induced changes in amyloid-β 40 and 42 plasma concentrations, while glymphatic function seems most important for change in plasma concentration of phosphorylated tau peptide 181 during sleep deprivation. Altogether, the present data highlight diverse mechanisms behind sleep-induced effects on concentrations of plasma neurodegeneration biomarkers.

• Åsberg, Anders; Hovd, Markus Herberg; Kjellevold, Stig Arne; Stenehjem, Aud Eldrid; Wien, Tale Norbye & Broch, Lars Ulrik [Show all 15 contributors for this article] (2023). Humoral Response After 6 or More Successive Doses of SARS-CoV-2 mRNA Vaccines in Kidney Transplant Recipients-Should We Keep Vaccinating? Transplantation. ISSN 0041-1337. 107(10), p. e279–e280. doi: 10.1097/TP.0000000000004732. Full text in Research Archive
• Hovd, Markus Herberg; Robertsen, Ida; Johnson, Line Kristin; Krogstad, Veronica; Wegler, Christine & Kvitne, Kine Eide [Show all 16 contributors for this article] (2023). Neither Gastric Bypass Surgery Nor Diet-Induced Weight-Loss Affect OATP1B1 Activity as Measured by Rosuvastatin Oral Clearance. Clinical Pharmacokinetics. ISSN 0312-5963. 62(5), p. 725–735. doi: 10.1007/s40262-023-01235-5. Full text in Research Archive Show summary

  Introduction Rosuvastatin pharmacokinetics is mainly dependent on the activity of hepatic uptake transporter OATP1B1. In this study, we aimed to investigate and disentangle the effect of Roux-en-Y gastric bypass (RYGB) and weight loss on oral clearance (CL/F) of rosuvastatin as a measure of OATP1B1-activity. Methods Patients with severe obesity preparing for RYGB (n = 40) or diet-induced weight loss (n = 40) were included and followed for 2 years, with four 24-hour pharmacokinetic investigations. Both groups underwent a 3-week low-energy diet (LED; < 1200 kcal/day), followed by RYGB or a 6-week very-low-energy diet (VLED; < 800 kcal/day). Results A total of 80 patients were included in the RYGB group (40 patients) and diet-group (40 patients). The weight loss was similar between the groups following LED and RYGB. The LED induced a similar (mean [95% CI]) decrease in CL/F in both intervention groups (RYGB: 16% [0, 31], diet: 23% [8, 38]), but neither induced VLED resulted in any further changes in CL/F. At Year 2, CL/F had increased by 21% from baseline in the RYGB group, while it was unaltered in the diet group. Patients expressing the reduced function SLCO1B1 variants (c.521TC/CC) showed similar changes in CL/F over time compared with patients expressing the wild-type variant. Conclusions Neither body weight, weight loss nor RYGB per se seem to affect OATP1B1 activity to a clinically relevant degree. Overall, the observed changes in rosuvastatin pharmacokinetics were minor, and unlikely to be of clinical relevance.

• Hovd, Markus Herberg; Åsberg, Anders; Munthe, Ludvig Andre; Heldal, Kristian; Reisæter, Anna Varberg & Vaage, John T. [Show all 8 contributors for this article] (2023). Humoral vaccine response and breakthrough infections in kidney transplant recipients during the COVID-19 pandemic: a nationwide cohort study. EClinicalMedicine. 60. doi: 10.1016/j.eclinm.2023.102035. Full text in Research Archive Show summary

  Background Kidney transplant recipients (KTRs) experienced reduced SARS-CoV-2 vaccine response and were at increased risk of severe COVID-19. It is unknown if level of vaccine induced anti-receptor binding domain IgG (anti-RBD IgG) correlates with protection from and survival following COVID-19. We aimed to evaluate the effect of vaccine response on risk of breakthrough infections (BTI) and COVID-19 death in KTRs. Methods We performed a nationwide study, examining the competing risk of SARS-CoV-2 infection, COVID-19 related/unrelated death, and vaccine efficacy as assessed by level of anti-RBD IgG response 4–10 weeks after each vaccination. The study included all KTR in Norway alive and with a functioning graft on February 20th, 2020, and events after November 11th, 2022 were right-censored. A pre-pandemic reference-cohort from January 1st 2019 to January 1st 2020 was included to evaluate excess mortality. The study was conducted at Oslo University Hospital, Rikshospitalet, Norway. Findings The study included 3607 KTRs (59 [48–70] years) with a functioning graft at February 20th, 2020, who received (median [IQR]) 4 [3–4] vaccines (range 2–6, 99% mRNA). Anti-RBD IgG was measured in 12 701 serum samples provided by 3213 KTRs. Vaccine response was assessed 41 [31–57] days after vaccination. A total of 1090 KTRs were infected with SARS-CoV-2, 1005 (92%) were BTI, and vaccine response did not protect against BTI. The hazard ratio for COVID-19 related death 40 days post-infection was 1.71 (95% CI: 1.14, 2.56) comparing vaccine response levels (≥5 vs. ≥5000 BAU/mL). No excess non-COVID-19 mortality was registered in KTRs surviving SARS-CoV-2 infection compared to a 2019 pre-pandemic reference. Interpretation Our findings suggested that SARS-CoV-2 mRNA vaccine response did not predict protection against infection, but prevention of fatal disease progression in KTRs and greater vaccine response further reduced the risk of COVID-19 death. No excess non-COVID-19 mortality was seen during the pandemic.

• Drevland, Ole Martin; Robertsen, Ida; Gustavsen, Marte Theie; Kveim, Hanne Kamilla; Hovd, Markus Herberg & Midtvedt, Karsten [Show all 7 contributors for this article] (2023). Impact of Fasting Status and Circadian Variation on the Pharmacokinetics of Mycophenolate Mofetil and the Glucuronide Metabolite in Renal Transplant Recipients. Transplantation direct. 9(3). doi: 10.1097/TXD.0000000000001448. Full text in Research Archive Show summary

  Background. Mycophenolate mofetil (MMF) is an immunosuppressive prodrug often used to prevent allograft rejection following solid organ transplantation. After oral administration, MMF is rapidly hydrolyzed to the active metabolite mycophenolate acid (MPA), which is inactivated by glucuronosyltransferase to the mycophenolic acid glucuronide metabolite (MPAG). The aim was 2-fold: to investigate the impact of circadian variation and fasting versus nonfasting status on MPA and MPAG pharmacokinetics in renal transplant recipients (RTRs). Methods. RTRs with stable graft function treated with tacrolimus, prednisolone, and MMF (750 mg BID) were included in this open, nonrandomized study. Two 12-h pharmacokinetic investigations were conducted in succession following morning and evening doses, both in a fasting and in a real-life nonfasting condition. Results. A total of 30 (22 men) RTRs performed one 24-h investigation, and 16 repeated the investigation within 1 mo. In a real-life nonfasting state, MPA area under the curve (AUC)0–12 and C0 failed to meet the bioequivalence criteria. Following the evening dose, mean MPA AUC12–24 was 16% lower (P < 0.001) compared with AUC0–12, and a shorter Tmax was observed (P = 0.09). Under fasting conditions, MPA AUC12–24 was 13% lower than AUC0–12, and the absorption rate was slower after the evening dose (P < 0.05). MPAG displayed circadian variation only under real-life conditions with lower AUC0–12 following the evening dose (P < 0.001). Conclusions. Both MPA and MPAG showed circadian variation with somewhat lower systemic exposures following the evening dose with limited clinical relevance in the dosing of MMF in RTRs. Fasting status affects MMF absorption rate differently, but with similar results in systemic exposure.

• Kvitne, Kine Eide; Hovd, Markus; Johnsen, Line Kristin; Wegler, Christine; Karlsson, Cecilia & Artursson, Per [Show all 14 contributors for this article] (2023). Digoxin Pharmacokinetics in Patients with Obesity Before and After a Gastric Bypass or a Strict Diet Compared with Normal Weight Individuals. Clinical Pharmacokinetics. ISSN 0312-5963. 63(1), p. 103–120. doi: 10.1007/s40262-023-01320-9. Full text in Research Archive Show summary

  Background and Objective Several drugs on the market are substrates for P-glycoprotein (P-gp), an efflux transporter highly expressed in barrier tissues such as the intestine. Body weight, weight loss, and a Roux-en-Y gastric bypass (RYGB) may influence P-gp expression and activity, leading to variability in the drug response. The objective of this study was therefore to investigate digoxin pharmacokinetics as a measure of the P-gp phenotype in patients with obesity before and after weight loss induced by an RYGB or a strict diet and in normal weight individuals. Methods This study included patients with severe obesity preparing for an RYGB (n = 40) or diet-induced weight loss (n = 40) and mainly normal weight individuals scheduled for a cholecystectomy (n = 18). Both weight loss groups underwent a 3-week low-energy diet (<1200 kcal/day) followed by an additional 6 weeks of <800 kcal/day induced by an RYGB (performed at week 3) or a very-low-energy diet. Follow-up time was 2 years, with four digoxin pharmacokinetic investigations at weeks 0, 3, and 9, and year 2. Hepatic and jejunal P-gp levels were determined in biopsies obtained from the patients undergoing surgery. Results The RYGB group and the diet group had a comparable weight loss in the first 9 weeks (13 ± 2.3% and 11 ± 3.6%, respectively). During this period, we observed a minor increase (16%) in the digoxin area under the concentration–time curve from zero to infinity in both groups: RYGB: 2.7 µg h/L [95% confidence interval (CI) 0.67, 4.7], diet: 2.5 µg h/L [95% CI 0.49, 4.4]. In the RYGB group, we also observed that the time to reach maximum concentration decreased after surgery: from 1.0 ± 0.33 hours at week 3 to 0.77 ± 0.08 hours at week 9 (−0.26 hours [95% CI −0.47, −0.05]), corresponding to a 25% reduction. Area under the concentration–time curve from zero to infinity did not change long term (week 0 to year 2) in either the RYGB (1.1 µg h/L [−0.94, 3.2]) or the diet group (0.94 µg h/L [−1.2, 3.0]), despite a considerable difference in weight loss from baseline (RYGB: 30 ± 7%, diet: 3 ± 6%). At baseline, the area under the concentration–time curve from zero to infinity was −5.5 µg h/L [95% CI −8.5, −2.5] (−26%) lower in patients with obesity (RYGB plus diet) than in normal weight individuals scheduled for a cholecystectomy. Further, patients undergoing an RYGB had a 0.05 fmol/µg [95% CI 0.00, 0.10] (29%) higher hepatic P-gp level than the normal weight individuals. Conclusions Changes in digoxin pharmacokinetics following weight loss induced by a pre-operative low-energy diet and an RYGB or a strict diet (a low-energy diet plus a very-low-energy diet) were minor and unlikely to be clinically relevant. The lower systemic exposure of digoxin in patients with obesity suggests that these patients may have increased biliary excretion of digoxin possibly owing to a higher expression of P-gp in the liver.

• Kvitne, Kine Eide; Krogstad, Veronica; Wegler, Christine; Johnson, Line Kristin; Kringen, Marianne K. & Hovd, Markus Herberg [Show all 19 contributors for this article] (2022). Short- and long-term effects of body weight, calorie restriction and gastric bypass on CYP1A2, CYP2C19 and CYP2C9 activity. British Journal of Clinical Pharmacology. ISSN 0306-5251. 88(9), p. 4121–4133. doi: 10.1111/bcp.15349. Full text in Research Archive Show summary

  Roux-en-Y gastric bypass (RYGB) may influence drug disposition due to surgery-induced gastrointestinal alterations and/or subsequent weight loss. The objective was to compare short- and long-term effects of RYGB and diet on the metabolic ratios of paraxanthine/caffeine (cytochrome P450 [CYP] 1A2 activity), 5-hydroxyomeprazole/omeprazole (CYP2C19 activity) and losartan/losartan carboxylic acid (CYP2C9 activity), and cross-sectionally compare these CYP-activities with normal-to-overweight controls. Methods This trial included patients with severe obesity preparing for RYGB (n = 40) or diet-induced (n = 41) weight loss, and controls (n = 18). Both weight loss groups underwent a 3-week low-energy diet (<1200 kcal/day, weeks 0-3) followed by a 6-week very-low-energy diet or RYGB (both <800 kcal/day, weeks 3-9). Follow-up time was 2 years, with four pharmacokinetic investigations. Results Mean ± SD weight loss from baseline was similar in the RYGB-group (13 ± 2.4%) and the diet group (10.5 ± 3.9%) at week 9, but differed at year 2 (RYGB −30 ± 6.9%, diet −3.1 ± 6.3%). From weeks 0 to 3, mean (95% confidence interval [CI]) CYP2C19 activity similarly increased in both groups (RYGB 43% [16, 55], diet 48% [22, 60]). Mean CYP2C19 activity increased by 30% (2.6, 43) after RYGB (weeks 3-9), but not in the diet-group (between-group difference −0.30 [−0.63, 0.03]). CYP2C19 activity remained elevated in the RYGB group at year 2. Baseline CYP2C19 activity was 2.7-fold higher in controls compared with patients with obesity, whereas no difference was observed in CYP1A2 and CYP2C9 activities. Conclusion Our findings suggest that CYP2C19 activity is lower in patients with obesity and increases following weight loss. This may be clinically relevant for drug dosing. No clinically significant effect on CYP1A2 and CYP2C9 activities was observed.

• Hovd, Markus Herberg; Mariussen, Espen; Uggerud, Hilde Thelle; Lashkarivand, Aslan; Christensen, Hege & Ringstad, Geir [Show all 7 contributors for this article] (2022). Population pharmacokinetic modeling of CSF to blood clearance: prospective tracer study of 161 patients under work-up for CSF disorders. Fluids and Barriers of the CNS. 19(1). doi: 10.1186/s12987-022-00352-w. Full text in Research Archive Show summary

  Background Quantitative measurements of cerebrospinal fluid to blood clearance has previously not been established for neurological diseases. Possibly, variability in cerebrospinal fluid clearance may affect the underlying disease process and may possibly be a source of under- or over-dosage of intrathecally administered drugs. The aim of this study was to characterize the cerebrospinal fluid to blood clearance of the intrathecally administered magnetic resonance imaging contrast agent gadobutrol (Gadovist, Bayer Pharma AG, GE). For this, we established a population pharmacokinetic model, hypothesizing that cerebrospinal fluid to blood clearance differs between cerebrospinal fluid diseases. Methods Gadobutrol served as a surrogate tracer for extra-vascular pathways taken by several brain metabolites and drugs in cerebrospinal fluid. We estimated cerebrospinal fluid to blood clearance in patients with different cerebrospinal fluid disorders, i.e. symptomatic pineal and arachnoid cysts, as well as tentative spontaneous intracranial hypotension due to cerebrospinal fluid leakage, idiopathic intracranial hypertension, or different types of hydrocephalus (idiopathic normal pressure hydrocephalus, communicating- and non-communicating hydrocephalus). Individuals with no verified cerebrospinal fluid disturbance at clinical work-up were denoted references. Results Population pharmacokinetic modelling based on 1,140 blood samples from 161 individuals revealed marked inter-individual variability in pharmacokinetic profiles, including differences in absorption half-life (time to 50% of tracer absorbed from cerebrospinal fluid to blood), time to maximum concentration in blood and the maximum concentration in blood as well as the area under the plasma concentration time curve from zero to infinity. In addition, the different disease categories of cerebrospinal fluid diseases demonstrated different profiles. Conclusions The present observations of considerable variation in cerebrospinal fluid to blood clearance between individuals in general and across neurological diseases, may suggest that defining cerebrospinal fluid to blood clearance can become a useful diagnostic adjunct for work-up of cerebrospinal fluid disorders. We also suggest that it may become useful for assessing clearance capacity of endogenous brain metabolites from cerebrospinal fluid, as well as measuring individual cerebrospinal fluid to blood clearance of intrathecal drugs.

• Eide, Per Kristian; Mariussen, Espen; Uggerud, Hilde Thelle; Pripp, Are Hugo; Lashkarivand, Aslan & Hassel, Bjørnar [Show all 9 contributors for this article] (2021). Clinical application of intrathecal gadobutrol for assessment of cerebrospinal fluid tracer clearance to blood. JCI Insight. 6(9), p. 1–13. doi: 10.1172/jci.insight.147063. Full text in Research Archive Show summary

  BACKGROUND. Methodology for estimation of cerebrospinal fluid (CSF) tracer clearance could have wide clinical application in predicting excretion of intrathecal drugs and metabolic solutes from brain metabolism and for diagnostic workup of CSF disturbances. METHODS. The MRI contrast agent gadobutrol (Gadovist) was used as a CSF tracer and injected into the lumbar CSF. Gadobutrol is contained outside blood vessels of the CNS and is eliminated along extravascular pathways, analogous to many CNS metabolites and intrathecal drugs. Tracer enrichment was verified and assessed in CSF by MRI at the level of the cisterna magna in parallel with obtaining blood samples through 48 hours. RESULTS. In a reference patient cohort (n = 29), both enrichment within CSF and blood coincided in time. Blood concentration profiles of gadobutrol through 48 hours varied between patients diagnosed with CSF leakage (n = 4), idiopathic normal pressure hydrocephalus dementia (n = 7), pineal cysts (n = 8), and idiopathic intracranial hypertension (n = 4). CONCLUSION. Assessment of CSF tracer clearance is clinically feasible and may provide a way to predict extravascular clearance of intrathecal drugs and endogenous metabolites from the CNS. The peak concentration in blood (at about 10 hours) was preceded by far peak tracer enhancement at MRI in extracranial lymphatic structures (at about 24 hours), as shown in previous studies, indicating a major role of the spinal canal in CSF clearance capacity. FUNDING. The work was supported by the Department of Neurosurgery, Oslo University Hospital; the Norwegian Institute for Air Research; and the University of Oslo.

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• Hovd, Markus Herberg; Mariussen, Espen; Uggerud, Hilde Thelle; Lashkarivand, Aslan; Christensen, Hege & Ringstad, Geir [Show all 7 contributors for this article] (2023). CSF to blood clearance differs substantially across individuals and patients with CSF disorders. Fluids and Barriers of the CNS. 19. doi: 10.1186/s12987-022-00397-x. Full text in Research Archive

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