Assessing the binding interaction of polystyrene sulfonate with amitriptyline in healthy volunteers: a cross-over design - The BIND study.

PURPOSE: Polystyrene sulfonate is used for binding potassium in patients with chronic kidney disease (CKD). Because of its binding properties, it can potentially bind other medications and thereby decrease their bioavailability and effectiveness. Amitriptyline, often used by CKD patients for neuropathic pain, shows significant binding to polystyrene sulfonate in vitro. The purpose of this study was to determine the effect of polystyrene sulfonate on the exposure of amitriptyline in vivo when taken concomitantly in healthy volunteers. METHODS: We performed a prospective cross-over study in nine healthy volunteers. Participants were 18 years of age or older, did not use any medication, and had no known allergy to amitriptyline or polystyrene sulfonate. Participants visited Deventer Teaching Hospital twice. Once they received a single dose of amitriptyline 50 mg and once they received a single dose of both polystyrene sulfonate 15 g and amitriptyline 50 mg taken concomitantly, with a wash out period of at least 1 week. After intake of the medication, six blood samples were collected, at 2, 3, 4, 5, 6, and 8 h. Blood samples were analysed to determine maximum concentration (Cmax) and area under the curve 0-8 h after intake (AUC0-8 h). Difference in Cmax and AUC0-8 h was analysed with a paired T-test or Wilcoxon signed rank test, depending on normality of the data. A p-value < 0.05 was considered statistically significant. RESULTS: Of the nine participants included, eight participants completed both visits to the hospital. Mean maximum concentration (Cmax) of amitriptyline was 35.61 µg l-1 (95% CI 27.90-43.33 µg l-1) when taken alone, compared to 9.25 µg l-1 (95% CI 6.59-11.92 µg l-1) when taken with polystyrene sulfonate (p < 0.001). Mean AUC0-8 h of amitriptyline was 168.20 µg × h l-1 (95% CI 139.95-196.45 µg × h l-1) when taken alone and 45.78 µg × h l-1 (95% CI 30.20-61.36 µg × h l-1) when taken with polystyrene sulfonate (p < 0.0001). CONCLUSION: These results show a significant decrease in exposure of amitriptyline of approximately 75% when taken concomitantly with polystyrene sulfonate, thereby probably compromising therapy efficacy. Patients using both amitriptyline and polystyrene sulfonate should be informed to separate intake of these medications. TRIAL REGISTRATION: NL8539 (17 April 2020).

Dosing oxaliplatin in a haemodialysis patient with metastatic rectum cancer monitored by free platinum concentrations.

WHAT IS KNOWN AND OBJECTIVE: Oxaliplatin in combination with fluorouracil and folinic acid is one of the preferred chemotherapeutic options in the treatment of metastatic rectum cancer. However, oxaliplatin is contraindicated in patients with a creatinine clearance <30 mL/min and dosing guidelines in patients on haemodialysis have not been established. CASE SUMMARY: A 77-year-old haemodialysis patient with metastatic rectum cancer was treated with FOLFOX and bevacizumab (oxaliplatin 70 mg/m2 , folinic acid 200 mg/m2 , 5-FU 340 mg/m2 bolus and 2040 mg/m2 continuous infusion during 44 hours and bevacizumab 5 mg/kg) every three weeks. Haemodialysis started immediately after infusion of oxaliplatin. The oxaliplatin dose was monitored by measuring free platinum ultrafiltrate concentrations. The AUC0-50 of free platinum plasma ultrafiltrate after cycles 1-3, respectively, was 24.3, 24.7 and 25.8 µg*h/mL. The Cmax was, respectively, 1.3, 1.3 and 2.2 µg/mL. There was no accumulation of free platinum detectable. The patient experienced no toxicity, and after 3 cycles, the CT scan showed a decrease in the liver metastases after which hemihepatectomy and metastasectomy were performed without any complications. A CT scan 6 months after the surgery showed no new liver metastases. However, lymphatic metastasis was diagnosed for which palliative treatment was started. WHAT IS NEW AND CONCLUSION: Dosing oxaliplatin in a haemodialysis patient monitored by free platinum concentrations was effective, safe and feasible in clinical practice. Further research is needed to determine the best pharmacokinetic parameter or combination of parameters and corresponding target values to further optimize the oxaliplatin dose for the individual haemodialysis patient.

Subtherapeutic serum quetiapine concentrations after absorption inhibition by binding resins: a case report.

WHAT IS KNOWN AND OBJECTIVE: Polystyrene sulfonate and sevelamer are binding resins that are used in the treatment of, respectively, hyperkalemia and hyperphosphatemia. It is unknown whether these resins interact with the antipsychotic quetiapine. CASE SUMMARY: We report on a woman with unexplainable low serum quetiapine concentrations who also used the binding resins polystyrene sulfonate and sevelamer. An In vitro binding assay showed binding of quetiapine by these resins. Separation of the ingestion times of quetiapine and the binding resins resulted in increased serum levels in this patient. WHAT IS NEW AND CONCLUSION: Polystyrene sulfonate and sevelamer are able to bind quetiapine. Healthcare professionals should be aware of this potential drug-drug interaction as this could lead to antipsychotic treatment failure.

Identification and analysis of a SMAD3 cis-acting eQTL operating in primary osteoarthritis and in the aneurysms and osteoarthritis syndrome.

OBJECTIVE: The TGF-ß pathway plays a central role in joint development with polymorphism in TGF-ß pathway genes implicated in osteoarthritis susceptibility. One association is to rs12901499, within intron 1 of SMAD3. Since rs12901499 is not in linkage disequilibrium with a non-synonymous polymorphism, it is likely the association is operating by influencing expression of SMAD3. DESIGN: Using tissues from the joints of primary osteoarthritis patients who had undergone joint replacement we measured the overall expression of SMAD3 by quantitative real-time PCR. We also measured allelic expression of SMAD3 using these tissues and vascular smooth muscle cells from patients with aneurysms and osteoarthritis syndrome, a rare condition featuring early-onset osteoarthritis. We tested the functional effect of SNPs in vitro using luciferase assays and assessed association with osteoarthritis using a large osteoarthritis case-control dataset. RESULTS: We observed that genotype at rs12901499 did not correlate with overall SMAD3 expression or allelic expression. However, genotype at a 3'UTR SNP, rs8031440, did correlate with SMAD3 expression in cartilage (P = 0.005) which was supported by allelic expression data showing that the G allele correlated with decreased SMAD3 expression in joint tissues and vascular smooth muscle cells. This G allele was underrepresented in osteoarthritis cases vs controls (P = 0.027, odds ratio = 0.921). rs8031440 is in perfect linkage disequilibrium with five other SMAD3 3'UTR SNPs and our luciferase analysis identified rs3743342 and rs12595334 as being functional. CONCLUSION: SMAD3 is subject to cis-acting regulatory polymorphism in the tissues of relevance to both primary osteoarthritis and the aneurysms-osteoarthritis syndrome.

Enzalutamide Reduces Oxycodone Exposure in Men with Prostate Cancer.

BACKGROUND AND OBJECTIVE: Up to 90% of patients with castration-resistant prostate cancer (CRPC) will develop symptomatic bone metastases requiring pain medication, with opioids being the mainstay of therapy in treating moderate and severe pain. Enzalutamide is an androgen receptor antagonist for the treatment of CRPC and a strong inducer of cytochrome P450 (CYP)3A4. Hereby, enzalutamide potentially reduces the exposure of oxycodone, an opioid metabolized by CYP3A4 and CYP2D6. Our objective was to evaluate the potential drug-drug interaction of enzalutamide and oxycodone. METHODS: A prospective, nonrandomized, open-label, two-arm parallel study was performed. All patients received a single dose of 15 mg normal-release oxycodone. Patients in the enzalutamide arm (ENZ-arm) received enzalutamide 160 mg once daily. Plasma concentrations of oxycodone and its metabolites were quantified using a validated liquid chromatography with tandem mass spectrometry (LC-MS/MS) method. RESULTS: Twenty-six patients (13 ENZ-arm; 13 control arm) were enrolled in the study. Enzalutamide decreased the mean AUC0-8 h and Cmax of oxycodone with, respectively, 44.7% (p < 0.001) and 35.5% (p = 0.004) compared with the control arm. The AUC0-8 h and Cmax of the active metabolite oxymorphone were 74.2% (p < 0.001) and 56.0% (p = 0.001) lower in the ENZ-arm compared with the control arm. In contrast, AUC0-8 h and Cmax of the inactive metabolites noroxycodone and noroxymorphone were significantly increased by enzalutamide. CONCLUSION: Co-administration of enzalutamide significantly reduced exposure to oxycodone and its active metabolite oxymorphone in men with prostate cancer. This should be taken into account when prescribing enzalutamide combined with oxycodone.

PTEN in colorectal cancer: a report on two Cowden syndrome patients.

Heterozygous germline PTEN mutations cause Cowden syndrome. The risk of colorectal cancer in Cowden patients, however, remains a matter of debate. We describe two patients presenting with colorectal cancer at a young age (28 and 39 years) and dysmorphisms fitting the Cowden spectrum. Heterozygous germline mutations in PTEN were found in both patients. Moreover, analysis of the resected colorectal cancer specimens revealed loss of heterozygosity at the PTEN locus with retention of the mutated alleles, and greatly reduced or absent PTEN expression. Histologically and molecularly, the tumours showed resemblance with sporadic colorectal cancers, although they had prominent fibrotic stroma. Our data indicate that PTEN loss was involved in carcinogenesis in the two patients, supporting that colorectal cancer is part of the Cowden syndrome-spectrum. This is in line with data on sporadic colorectal cancer, mice studies and emerging epidemiological data on Cowden syndrome. Although the exact role of germline PTEN mutations in the carcinogenesis of colorectal cancer remains unclear, we think that Cowden syndrome should be in the differential diagnosis of colorectal cancer certainly in view of the possible prognostic and therapeutic consequences. Prospective follow-up and surveillance of PTEN mutation carriers from the age of 25 to 30 years in a study setting should clarify this issue.

Exploring co-dispensed drug use in patients on sevelamer or polystyrene sulfonate to identify potential novel binding interactions: a cross sectional in silico study : Potential novel binding interactions with resins.

Background Sevelamer and polystyrene sulfonate are used for treating hyperphosphatemia and hyperkalaemia in chronic kidney disease patients. Because of their binding properties, these resins potentially bind other drugs in the gastrointestinal tract, thereby decreasing their bioavailability and clinical effectiveness. Aim The aim of this study was to explore co-dispensed drug use in patients on sevelamer or polystyrene sulfonate to identify potential novel binding interactions. Method In this in silico study, the 100 drugs most frequently co-dispensed with sevelamer/polystyrene sulfonate in the period 2000-2018 were extracted from the University Groningen IADB.nl database. Drugs dispensed to < 5% of patients, drugs not orally administered, drugs administered once daily before bedtime and drugs for which information on binding interactions with sevelamer or polystyrene was already available were excluded. The likelihood of an interaction (yes or no) of the included drugs was assessed based on pKa- and Log P values. For sevelamer, drugs with a pKa (acid) between 1.5 and 7.4 and or a Log P value > 2.0 were identified as potential interacting drug. For polystyrene sulfonate, drugs with a pKa (base) > 1.5 were identified as potential interacting drug. Results Of the top 100 drugs most frequently co-dispensed with sevelamer/polystyrene sulfonate, 22 and 27 potentially clinically relevant new interacting drugs were identified for sevelamer and polystyrene sulfonate respectively. Conclusion Several potentially relevant novel binding interactions for sevelamer and polystyrene sulfonate were identified based on dispensing data and assessment of chemical properties for which further interaction research is warranted.

Metformin associated lactic acidosis: incidence and clinical correlation with metformin serum concentration measurements.

WHAT IS KNOWN AND OBJECTIVE: The reported incidence of metformin associated lactic acidosis (MALA) in type 2 diabetes mellitus (DM) is 3-9 cases per 100,000 patient-years. In clinical practice, 22-94% of patients using metformin have contraindications to metformin, so the incidence of MALA may be higher than reported. AIM OF THE STUDY: To estimate the incidence of MALA in type 2 DM patients by means of metformin serum concentration measurements and investigate the correlation of metformin serum concentration with the clinical outcome of MALA. METHODS: MALA cases were identified by reviewing the medical records of patients with metformin serum concentrations measured between January 2000 and October 2008. MALA was defined as arterial pH <7·35 and lactate concentration >5·0 mmol/L in patients using metformin. The incidence of MALA was calculated from the number of cases and the at risk population. The correlation coefficient between the metformin and lactate concentration was calculated by linear regression. The relationship between metformin serum concentration, lactate concentration and outcome was examined by calculating the mean metformin and lactate concentration in patients who survived and those who died. The Student's t-test was used to compare groups. RESULTS AND DISCUSSION: In 29 patients metformin serum concentration was measured, 16 had MALA. Eleven of the 16 MALA cases (69%) had risk factors for lactic acidosis in their medical history, 13 cases (81%) had renal failure on admission. The incidence of MALA was estimated at 47 per 100,000 patient-years, this is 5-16 times higher than previously reported. This may be explained by the use of metformin in the presence of risk factors for lactic acidosis. Survivors had a higher metformin serum concentration (18·9 mg/L) than non-survivors (2·9 mg/L, P = 0·006) which can be explained by less severe underlying disease in patients who survived MALA, rather than an effect of metformin itself. WHAT IS NEW AND CONCLUSION: The incidence of MALA estimated from metformin serum concentration measurements in type 2 DM patients is 5-16 times higher than reported in literature. MALA is probably caused by the frequent use of metformin in the presence of risk factors for lactic acidosis. Metformin serum concentration measurements may aid in the timely diagnosis and therapy of MALA. The outcome of MALA is determined by the severity of the underlying disease, rather than by metformin itself.

Identifying patients with metformin associated lactic acidosis in the emergency department.

Background Metformin associated lactic acidosis (MALA) is a serious adverse event with a high mortality rate of 30-50%. Early recognition of MALA and timely starting treatment may reduce its morbidity and mortality. Objective The aim of this study was to explore clinical parameters to identify patients with MALA in patients with suspected sepsis induced lactic acidosis in the emergency department ED. Setting A retrospective single centre study was conducted at the Deventer Teaching Hospital in the Netherlands. Method Patients with lactate concentration > 4.0 mmol/l admitted at the ED between 2010 and 2017 with suspected sepsis or confirmed MALA and referred to the Intensive Care Unit were included. Baseline characteristics (pH, lactate, creatinine and CRP) of MALA patients were compared with patients with suspected sepsis induced lactic acidosis. Creatinine and lactate concentration were selected as potential relevant parameters. Main outcome measure Sensitivity and specificity of the highest tertiles of the creatinine and the lactate concentrations separately, in combination, and both combined with metformin use, were calculated. Results Thirteen MALA and 90 suspected sepsis induced lactic acidosis patients were included. Lactate (14.7 vs 5.9 mmol/l, p < 0.01) and creatinine concentration (642 vs 174 µmol/l, p < 0.01) were significantly higher in the MALA group and arterial pH (7.04 vs 7.38, p < 0.01) and CRP (90 vs 185 mg/l, p < 0.01) were significantly lower. The combined parameters lactate ≥ 8.4 mmol/l, creatinine ≥ 256 µmol/l had a sensitivity of 85% and a specificity of 95% for identifying MALA in suspected sepsis induced lactic acidosis patients in the ED. When combined with metformin use the specificity increased to 99%. Conclusion When managing lactic acidosis in the ED the diagnosis MALA should be considered in patients with a creatinine concentration ≥ 256 µmol/l and lactate concentration ≥ 8.4 mmol/l.

Mapping of 5q35 chromosomal rearrangements within a genomically unstable region.

BACKGROUND: Recent molecular studies of breakpoints of recurrent chromosome rearrangements revealed the role of genomic architecture in their formation. In particular, segmental duplications representing blocks of >1 kb with >90% sequence homology were shown to mediate non-allelic homologous recombination (NAHR). However, the occurrence of the majority of newly detected submicroscopic imbalances cannot be explained by the presence of segmental duplications. Therefore, further studies are needed to investigate whether architectural features other than segmental duplications mediate these rearrangements. METHODS: We analysed a series of patients with breakpoints clustering within chromosome band 5q35. Using high density arrays and subsequent quantitative polymerase chain reaction (qPCR), we characterised the breakpoints of four interstitial deletions (including one associated with an unbalanced paracentric inversion), a duplication and a familial reciprocal t(5;18)(q35;q22) translocation. RESULTS AND CONCLUSION: Five of the breakpoints were located within an interval of approximately 265 kb encompassing the RANBP17 and TLX3 genes. This region is also targeted by the recurrent cryptic t(5;14)(q35;q32) translocation, which occurs in approximately 20% of childhood T cell acute lymphoblastic leukaemia (T-ALL). In silico analysis indicated the architectural features most likely to contribute to the genomic instability of this region, which was supported by our molecular data. Of further interest, in two patients and the familial translocation, the delineated breakpoint regions encompassed highly homologous LINEs (long interspersed nuclear elements), suggesting that NAHR between these LINEs may have mediated these rearrangements.

Microcephaly and simplified gyral pattern of the brain associated with early onset insulin-dependent diabetes mellitus.

Two families are presented with a child suffering from microcephaly with a simplified gyral pattern of the brain (SGP) and early onset insulin dependent diabetes mellitus (IDDM). The first patient was diagnosed postmortally with Wolcott-Rallison syndrome, after her younger brother developed IDDM, and a homozygous mutation in the eukaryotic translation initiation factor 2-alpha kinase 3 was found. The younger brother did not undergo magnetic resonance imaging (MRI). The patient from the second family has no EIF2AK3 mutation. SGP is considered to arise from decreased neuronal proliferation or increased apoptosis at an early stage of embryonal development, but insight into the pathways involved is minimal. EIF2AK3 is involved in translation initiation. It has been proposed that loss of function mutations reduce the ability of the cell to respond to endoplasmic reticulum stress, resulting in apoptosis of pancreatic Langerhans cells. Our findings suggest that in some cases, early onset IDDM and SGP can arise from common mechanisms leading to increased apoptosis.

Diploid/triploid mosaicism in dysmorphic patients.

Diploid/triploid mosaicism is a dysmorphology syndrome consisting of mental retardation, truncal obesity, body and/or facial asymmetry, growth retardation, hypotonia, a small phallus, malformed low-set ears and micrognathia. In 75% of the cases, the blood karyotype is normal and the diagnosis can only be established after analysis of cultured fibroblasts. This chromosome abnormality may therefore be underdiagnosed. This paper focuses on the identification of mentally retarded and dysmorphic patients with diploid/triploid mosaicism. Detailed clinical description of well-defined patients may help in deciding if a skin biopsy for karyotyping of fibroblasts should be taken. Three new cases are presented, in which DNA marker analysis showed that the extra set of chromosomes in each case was derived from the mother. We present a review of 25 cases described in the literature and we discuss the inclusion of a second polar body into an early diploid embryo as the most likely mechanism.