Molecular Basis for Ligand Modulation of a Mammalian Voltage-Gated Ca2+ Channel.

The L-type voltage-gated Ca2+ (Cav) channels are modulated by various compounds exemplified by 1,4-dihydropyridines (DHP), benzothiazepines (BTZ), and phenylalkylamines (PAA), many of which have been used for characterizing channel properties and for treatment of hypertension and other disorders. Here, we report the cryoelectron microscopy (cryo-EM) structures of Cav1.1 in complex with archetypal antagonistic drugs, nifedipine, diltiazem, and verapamil, at resolutions of 2.9 Å, 3.0 Å, and 2.7 Å, respectively, and with a DHP agonist Bay K 8644 at 2.8 Å. Diltiazem and verapamil traverse the central cavity of the pore domain, directly blocking ion permeation. Although nifedipine and Bay K 8644 occupy the same fenestration site at the interface of repeats III and IV, the coordination details support previous functional observations that Bay K 8644 is less favored in the inactivated state. These structures elucidate the modes of action of different Cav ligands and establish a framework for structure-guided drug discovery.

Mapping human microbiome drug metabolism by gut bacteria and their genes.

Individuals vary widely in their responses to medicinal drugs, which can be dangerous and expensive owing to treatment delays and adverse effects. Although increasing evidence implicates the gut microbiome in this variability, the molecular mechanisms involved remain largely unknown. Here we show, by measuring the ability of 76 human gut bacteria from diverse clades to metabolize 271 orally administered drugs, that many drugs are chemically modified by microorganisms. We combined high-throughput genetic analyses with mass spectrometry to systematically identify microbial gene products that metabolize drugs. These microbiome-encoded enzymes can directly and substantially affect intestinal and systemic drug metabolism in mice, and can explain the drug-metabolizing activities of human gut bacteria and communities on the basis of their genomic contents. These causal links between the gene content and metabolic activities of the microbiota connect interpersonal variability in microbiomes to interpersonal differences in drug metabolism, which has implications for medical therapy and drug development across multiple disease indications.

Diltiazem inhibits SARS-CoV-2 cell attachment and internalization and decreases the viral infection in mouse lung.

The continuous emergence of severe acute respiratory coronavirus 2 (SARS-CoV-2) variants and the increasing number of breakthrough infection cases among vaccinated people support the urgent need for research and development of antiviral drugs. Viral entry is an intriguing target for antiviral drug development. We found that diltiazem, a blocker of the L-type calcium channel Cav1.2 pore-forming subunit (Cav1.2 α1c) and an FDA-approved drug, inhibits the binding and internalization of SARS-CoV-2, and decreases SARS-CoV-2 infection in cells and mouse lung. Cav1.2 α1c interacts with SARS-CoV-2 spike protein and ACE2, and affects the attachment and internalization of SARS-CoV-2. Our finding suggests that diltiazem has potential as a drug against SARS-CoV-2 infection and that Cav1.2 α1c is a promising target for antiviral drug development for COVID-19.

Platelet-activating factor contracts guinea pig esophageal muscularis mucosae by stimulating extracellular Ca2+ influx through diltiazem-insensitive Ca2+ channels.

Platelet-activating factor (PAF) is expected to increase esophageal motility. However, to the best of our knowledge, this has not been examined. Thus, we investigated the contractile effects of PAF on guinea pig (GP) esophageal muscularis mucosae (EMM) and the extracellular Ca2+ influx pathways responsible. PAF (10-9-10-6 M) contracted EMM in a concentration-dependent manner. PAF (10-6 M)-induced contractions were almost completely suppressed by apafant (a PAF receptor antagonist, 3 × 10-5 M). In EMM strips, PAF receptor and PAF-synthesizing/degrading enzyme mRNAs were detected. PAF (10-6 M)-induced contractions were abolished by extracellular Ca2+ removal but were not affected by diltiazem [a voltage-dependent Ca2+ channel (VDCC) inhibitor, 10-5 M]. PAF (10-6 M)-induced contractions in the presence of diltiazem were significantly suppressed by LOE-908 [a receptor-operated Ca2+ channel (ROCC) inhibitor, 3 × 10-5 M], SKF-96365 [an ROCC and store-operated Ca2+ channel (SOCC) inhibitor, 3 × 10-5 M], and LOE-908 plus SKF-96365. Among the tested ROCC/SOCC-related mRNAs, Trpc3, Trpc6, and Trpv4/Orai1, Orai3, and Stim2 were abundantly expressed in EMM strips. These results indicate that PAF potently induces GP EMM contractions that are dependent on extracellular Ca2+ influx through ROCCs/SOCCs, and VDCCs are unlikely to be involved.

Relaxant Effects of Piperine and Piperlongumine from Piper longum Fruits on Porcine Coronary Artery.

Since ancient times, Piper longum Linn. fruits have been recognized for exhibiting various effects, including the diaphoretic effects linked to enhanced blood flow. Piperine and piperlongumine coexist in Piper longum Linn. fruits, although the cardiovascular effects of both compounds remain elusive. We investigated their action of piperine and piperlongumine in porcine coronary arteries, comparing them to the Ca2+ channel antagonist diltiazem. Piperlongumine, unlike piperine or diltiazem, concentration-dependently inhibited basal contractile tone in endothelium-denuded coronary arteries. All three compounds inhibit tonic contractions induced by high potassium chloride (KCl) concentrations. The order of relaxation potency indexed by the half-maximal effective concentration (EC50) were as follows: diltiazem > piperlongumine > piperine. These effects were not different between endothelium-intact and -denuded preparations. In endothelial-denuded preparations, pretreatment with these compounds not only inhibited KCl-induced tonic contractions attenuated calcium chloride (CaCl2)-induced ones in a Ca2+-free medium. Histamine-induced phasic contractions in a Ca2+-free medium containing intracellular Ca2+ chelator was completely suppressed by selective inositol trisphosphate receptor antagonist and piperlongumine, whereas piperine or diltiazem do not have the same effect. These findings suggest that piperine and piperlongumine similar to diltiazem cause vasorelaxation by inhibiting both KCl- and CaCl2-induced contractions in coronary arteries, possibly through the inhibition of voltage-dependent Ca2+ channels. Piperlongumine inhibits histamine-induced contractions in a Ca2+-free medium, which is associated with the intracellular Ca2+ signaling pathway, suggesting that the relaxant effect of piperlongumine differs from that of piperine.

Utility of native emission quenching of erythrosine B for the determination of diltiazem in different dosage forms.

This study introduces a practical and cost-effective method for tracking diltiazem (DLZ) analytically. It utilizes a fluorimetric approach that relies on the modulation of fluorescence intensity of a dye called erythrosine B. Through a one-pot experiment performed in an acidic environment, a complex is rapidly formed between DLZ and erythrosine B. By observing the decrease in erythrosine B emission, a linear calibration plot is established, enabling the detection and quantification of DLZ concentrations ranging from 40 to 850 ng/ml. The estimated limits of detection and quantitation were 10.5 and 32.1 ng/ml, respectively. The variables affecting the DLZ-dye complex system were carefully adjusted. The validity of the approach was confirmed through a thorough evaluation based on the criteria set by ICH guidelines. The accuracy and precision of the methodology were evaluated, and the standard deviation and relative standard deviation were below 2. The strategy was successfully employed to analyze DLZ in tablets and capsules, and no significant variation between the proposed and reported methods as the values of the estimated t-test and F-test at five determinations were below 2.306 and 6.338, respectively. Notably, the method adheres to the principle of green chemistry by utilizing distilled water as the dispersing medium.

Exploring the Effectiveness of Carboxymethylated and Crosslinked Albizia procera Gum in Diltiazem Hydrochloride Matrix Tablets: A Comparative Analysis.

This study investigates the efficacy of modified Albizia procera gum as a release-retardant polymer in Diltiazem hydrochloride (DIL) matrix tablets. Carboxymethylated Albizia procera gum (CAP) and ionically crosslinked carboxymethylated Albizia procera gum (Ca-CAP) were utilized, with Ca-CAP synthesized via crosslinking CAP with calcium ions (Ca2+) using calcium chloride (CaCl2). Fourier Transform (FT) IR analysis affirmed polymer compatibility, while differential scanning calorimetry (DSC) and X-ray diffraction (XRD) assessed thermal behavior and crystallinity, respectively. Zeta potential analysis explored surface charge and electrostatic interactions, while rheology examined flow and viscoelastic properties. Swelling and erosion kinetics provided insights into water penetration and stability. CAP's carboxymethyl groups (-CH2-COO-) heightened divalent cation reactivity, and crosslinking with CaCl2 produced Ca-CAP through -CH2-COO- and Ca2+ interactions. Structural similarities between the polymers were revealed by FTIR, with slight differences. DSC indicated modified thermal behavior in Ca-CAP, while Zeta potential analysis showcased negative charges, with Ca-CAP exhibiting lower negativity. XRD highlighted increased crystallinity in Ca-CAP due to calcium crosslinking. Minimal impact on RBC properties was observed with both polymers compared to the positive control as water for injection (WFI). Ca-CAP exhibited improved viscosity, strength, controlled swelling, and erosion, allowing prolonged drug release compared to CAP. Stability studies confirmed consistent six-month drug release, emphasizing Ca-CAP's potential as a stable, sustained drug delivery system over CAP. Robustness and accelerated stability tests supported these findings, underscoring the promise of Ca-CAP in controlled drug release applications.

Serious Bleeding in Patients With Atrial Fibrillation Using Diltiazem With Apixaban or Rivaroxaban.

Importance: Diltiazem, a commonly prescribed ventricular rate-control medication for patients with atrial fibrillation, inhibits apixaban and rivaroxaban elimination, possibly causing overanticoagulation. Objective: To compare serious bleeding risk for new users of apixaban or rivaroxaban with atrial fibrillation treated with diltiazem or metoprolol. Design, Setting, and Participants: This retrospective cohort study included Medicare beneficiaries aged 65 years or older with atrial fibrillation who initiated apixaban or rivaroxaban use and also began treatment with diltiazem or metoprolol between January 1, 2012, and November 29, 2020. Patients were followed up to 365 days through November 30, 2020. Data were analyzed from August 2023 to February 2024. Exposures: Diltiazem and metoprolol. Main Outcomes and Measures: The primary outcome was a composite of bleeding-related hospitalization and death with recent evidence of bleeding. Secondary outcomes were ischemic stroke or systemic embolism, major ischemic or hemorrhagic events (ischemic stroke, systemic embolism, intracranial or fatal extracranial bleeding, or death with recent evidence of bleeding), and death without recent evidence of bleeding. Hazard ratios (HRs) and rate differences (RDs) were adjusted for covariate differences with overlap weighting. Results: The study included 204 155 US Medicare beneficiaries, of whom 53 275 received diltiazem and 150 880 received metoprolol. Study patients (mean [SD] age, 76.9 [7.0] years; 52.7% female) had 90 927 person-years (PY) of follow-up (median, 120 [IQR, 59-281] days). Patients receiving diltiazem treatment had increased risk for the primary outcome (RD, 10.6 [95% CI, 7.0-14.2] per 1000 PY; HR, 1.21 [95% CI, 1.13-1.29]) and its components of bleeding-related hospitalization (RD, 8.2 [95% CI, 5.1-11.4] per 1000 PY; HR, 1.22 [95% CI, 1.13-1.31]) and death with recent evidence of bleeding (RD, 2.4 [95% CI, 0.6-4.2] per 1000 PY; HR, 1.19 [95% CI, 1.05-1.34]) compared with patients receiving metoprolol. Risk for the primary outcome with initial diltiazem doses exceeding 120 mg/d (RD, 15.1 [95% CI, 10.2-20.1] per 1000 PY; HR, 1.29 [95% CI, 1.19-1.39]) was greater than that for lower doses (RD, 6.7 [95% CI, 2.0-11.4] per 1000 PY; HR, 1.13 [95% CI, 1.04-1.24]). For doses exceeding 120 mg/d, the risk of major ischemic or hemorrhagic events was increased (HR, 1.14 [95% CI, 1.02-1.27]). Neither dose group had significant changes in the risk for ischemic stroke or systemic embolism or death without recent evidence of bleeding. When patients receiving high- and low-dose diltiazem treatment were directly compared, the HR for the primary outcome was 1.14 (95% CI, 1.02-1.26). Conclusions and Relevance: In Medicare patients with atrial fibrillation receiving apixaban or rivaroxaban, diltiazem was associated with greater risk of serious bleeding than metoprolol, particularly for diltiazem doses exceeding 120 mg/d.

Glucocorticoid effects on working memory impairment require l-type calcium channel activity within prefrontal cortex.

Previous findings have indicated that glucocorticoid hormones impair working memory via an interaction with the ß-adrenoceptor-cAMP signaling cascade to rapidly increase cAMP-dependent protein kinase (PKA) activity within the prefrontal cortex (PFC). However, it remains elusive how such activation of PKA can affect downstream cellular mechanisms in regulating PFC cognitive function. PKA is known to activate l-type voltage-gated Ca2+ channels (LTCCs) which regulate a broad range of cellular processes, including neuronal excitability and neurotransmitter release. The present experiments examined whether LTCC activity within the PFC is required in mediating glucocorticoid and PKA effects on spatial working memory. Male Sprague Dawley rats received bilateral administration of the LTCC inhibitor diltiazem together with either the glucocorticoid receptor agonist RU 28362 or PKA activator Sp-cAMPS into the PFC before testing on a delayed alternation task in a T-maze. Both RU 28362 and Sp-cAMPS impaired working memory, whereas the LTCC inhibitor diltiazem fully blocked the working memory impairment induced by either RU 28362 or Sp-cAMPS. Conversely, bilateral administration of the LTCC agonist Bay K8644 into the PFC was sufficient to impair working memory. Thus, these findings provide support for the view that glucocorticoids, via an interaction with the ß-adrenergic signaling cascade and enhanced PKA activity levels, impair working memory by increasing LTCC activity in the PFC.

Topical Lidocaine or Lidocaine/Diltiazem Ointment Following Rubber Band Ligation of Hemorrhoids: A Prospective 3-Armed Randomized Controlled Trial.

BACKGROUND: Rubber band ligation of hemorrhoids causes less pain than excisional hemorrhoidectomy, but many patients still experience significant postprocedure discomfort. OBJECTIVE: This study aimed to determine whether topical lidocaine, with or without diltiazem, is more effective than placebo for analgesia after hemorrhoid banding. DESIGN: This is a prospective, randomized, double-blinded, placebo-controlled trial. Patients were randomly assigned to 2% lidocaine, 2% lidocaine with 2% diltiazem, or a placebo ointment. SETTINGS: This study was performed at 2 university public teaching hospitals and 2 private hospitals in Australia. PATIENTS: Consecutive patients aged ≥18 years undergoing hemorrhoid banding were selected. INTERVENTIONS: Topical ointments were applied postprocedure 3× daily for 5 days. MAIN OUTCOME MEASURES: Visual analog pain score, opiate analgesia usage, and patient satisfaction were the main outcome measures. RESULTS: Of 159 eligible patients, 99 were randomly assigned (33 in each group). Pain scores were reduced at 1 hour for the lidocaine (OR 4.15 [1.12-15.41]; p = 0.03) and lidocaine/diltiazem groups (OR 3.85 [1.05-14.11]; p = 0.04) compared with placebo. Patients in the lidocaine/diltiazem group had improved satisfaction (OR 3.82 [1.28-11.44]; p = 0.02) and were more likely to recommend the procedure to others (OR 9.33 [1.07-81.72]; p = 0.04). Patients in the lidocaine/diltiazem group required approximately 45% less total and in-hospital analgesia compared with the placebo. There was no difference in complications between any of the groups. LIMITATIONS: A cost/benefit analysis was not performed. Analgesic efficacy appeared to be short term and the procedures were performed only in the hospital/nonambulatory setting. CONCLUSIONS: Topical lidocaine reduced short-term analgesia use, whereas combination lidocaine/diltiazem was associated with both improved analgesia and patient satisfaction after hemorrhoid banding. LIDOCANA TPICA O UNGENTO DE LIDOCANA/DILTIAZEM DESPUS DE LA LIGADURA HEMORROIDAL CON BANDA ELSTICA UN ENSAYO PROSPECTIVO CONTROLADO Y ALEATORIZADO DE TRES BRAZOS: ANTECEDENTES:La ligadura de hemorroides con banda elástica causa menos dolor que la hemorroidectomía escisional, pero muchos pacientes siguen experimentando molestias significativas tras el procedimiento.OBJETIVO:Este estudio tiene como objetivo determinar si la lidocaína tópica, con o sin diltiazem, es más eficaz que el placebo para la analgesia tras la ligadura hemorroidal.DISEÑO:Este es un ensayo prospectivo, aleatorizado, doble ciego, controlado con placebo. Los pacientes fueron aleatorizados para recibir lidocaína al 2 %, lidocaína al 2 % con diltiazem al 2 % o ungüento de placebo.AJUSTES:Este estudio se realizó en dos hospitales públicos con docencia universitaria y dos hospitales privados en Australia.PACIENTES:Se seleccionaron pacientes consecutivos de ≥18 años sometidos a ligadura para hemorroides.INTERVENCIONES:Se aplicaron ungüentos tópicos tras el procedimiento tres veces al día durante 5 días.PRINCIPALES MEDIDAS DE RESULTADO:La puntuación analógica visual del dolor, el uso de analgésicos opiáceos y la satisfacción del paciente fueron las principales medidas de resultado.RESULTADOS:De 159 pacientes elegibles, 99 fueron aleatorizados (33 en cada grupo). Las puntuaciones de dolor se redujeron a la hora para los grupos de lidocaína (OR 4,15 (1,12-15,41); p = 0,03) y lidocaína/diltiazem (OR 3,85 (1,05-14,11), p = 0,04) en comparación con el placebo.Los pacientes del grupo de lidocaína/diltiazem mejoraron su satisfacción (OR 3,82 (1,28-11,44), p = 0,02) y eran más propensos de recomendar el procedimiento a otros (OR 9,33 (1,07-81,72), p = 0,04). Los pacientes del grupo de lidocaína/diltiazem requirieron aproximadamente un 45 % menos de analgesia total e intrahospitalaria en comparación con el grupo de placebo. No hubo diferencia en las complicaciones entre ninguno de los grupos.LIMITACIONES:No se realizó un análisis de costo/beneficio. La eficacia analgésica pareció ser a corto plazo y los procedimientos solo se realizaron en el hospital/entorno no ambulatorio.CONCLUSIÓN:La lidocaína tópica mejora la analgesia a corto plazo, mientras que la combinación de lidocaína/diltiazem se asocia tanto con una mejor analgesia como con la satisfacción del paciente tras la colocación de bandas para hemorroides. (Traducción-Dr Osvaldo Gauto ).

DOsing Strategy Effectiveness of Diltiazem in Atrial Fibrillation With Rapid Ventricular Response.

STUDY OBJECTIVE: To evaluate the dose-dependent comparative safety and effectiveness between weight-based and alternative dosing strategies for diltiazem in atrial fibrillation with rapid ventricular response. METHODS: This retrospective cohort study included adult patients presenting to the emergency department (ED) with atrial fibrillation with rapid ventricular response who received treatment with intravenous diltiazem. Groups were retrospectively categorized according to the initial dose: low (<0.1875 mg/kg), weight-based (0.1875 to 0.3125 mg/kg), and high (>0.3125 mg/kg). The primary outcome was rate control (heart rate <100 beats/min) within 30 minutes of treatment. RESULTS: Of 345 records, 252 were included. Because of scarcity (N=6), outcomes for the high-dose group were not analyzed. By 30 minutes, the weight-based dosing group had more often achieved rate control (weight-based 55%; low 27%; difference 29% [95% confidence interval (CI) 17% to 40%]). Regression analysis identified the weight-based dosing group (odds ratio 3.63, 95% CI 2.06 to 6.39) and initial heart rate of less than 145 beats/min (odds ratio 2.56, 95% CI 1.46 to 4.51) as variables associated with the primary outcome. The weight-based dosing group less often required rescue therapy (weight-based 6%; low 17%; difference -12% [95% CI -20% to -4%]) relative to the low-dose group. Mortality was higher in the low-dose group than in the weight-based dosing group (low 7%; weight-based 1%; difference 6% [95% CI 1% to 11%]). CONCLUSION: This study shows dose-dependent hemodynamic effects with diltiazem in patients with atrial fibrillation with rapid ventricular response. Weight-based diltiazem (0.25 mg/kg) was associated with greater rate control with no evidence of increased adverse effects. There was no perceived advantage in using lower, alternative doses.

Comparing the efficacy and safety of different analgesic strategies after open hemorrhoidectomy: a systematic review and network meta-analysis.

PURPOSE: To evaluate the clinical efficacy and safety of different analgesic interventions in the treatment of pain after open hemorrhoidectomy by systematic review and network meta-analysis. METHODS: Randomized controlled trials that met the inclusion criteria in PubMed, Cochrane Library, Embase, Web of Science, Scopus, CNKI, WANFANG DATA, and VIP were searched from the date of database construction to June 28, 2022. RESULTS: Among the 13 randomized controlled trials (RCTs), 731 patients were included in the network meta-analysis. Most interventions are more effective than placebo in relieving postoperative pain. 24 h postoperative Visual Analogue Scale (VAS): glyceryl trinitrate (GTN) (mean difference (MD) - 4.20, 95% CI - 5.35, - 3.05), diltiazem (MD - 1.97, 95% CI - 2.44, - 1.51), botulinum toxin (BT) (MD - 1.50, 95% CI - 2.25, - 0.75), sucralfate (MD - 1.01, 95% CI - 1.53, - 0.49), and electroacupuncture (EA) (MD - 0.45, 95% CI - 0.87, - 0.04). 48 h postoperative VAS: diltiazem (MD - 2.45, 95% CI - 2.74, - 2.15), BT (MD - 2.18, 95% CI - 2.52, - 1.84), and sucralfate (MD - 1.41, 95% CI - 1.85, - 0.97). 7 d postoperative VAS: diltiazem (MD - 2.49, 95% CI - 3.20, - 1.78) and sucralfate (MD - 1.42, 95% CI - 2.00, - 0.85). The first postoperative defecation VAS: EA (MD - 0.70, 95% CI - 0.95, - 0.46). There are few data on intervention safety, and additional high-quality RCTs are expected to study this topic in the future. CONCLUSION: Diltiazem ointment may be the most effective medication for pain relief following open hemorrhoidectomy, and it can dramatically reduce pain within one week of surgery. The second and third recommended medications are BT and sucralfate ointment. GTN has a significant advantage in alleviating pain 24 h after open hemorrhoidectomy, but whether it causes headache is debatable; thus, it should be used with caution. EA's analgesic efficacy is still unknown. There was limited evidence on the safety of the intervention in this study, and it was simply presented statistically.

Can Targeting Sphincter Spasm Reduce Post-Haemorrhoidectomy Pain? A Systematic Review and Meta-Analysis.

BACKGROUND: Haemorrhoidectomy is often complicated by significant post-operative pain, to which spasm of the internal anal sphincter is thought to be a contributing factor. This study appraises the evidence behind interventions aimed at lowering sphincter spasm to relieve post-haemorrhoidectomy pain. METHODS: A Preferred Reporting Items for Systematic Reviews and Meta-analyses compliant systematic review was conducted. Medline, EMBASE, and CENTRAL databases were systematically searched. All RCTs which compared interventions targeting the internal anal sphincter to relieve pain post excisional haemorrhoidectomy were included. The primary outcome measure was pain on the visual analogue scale. RESULTS: Of the initial 10,221 search results, 39 articles were included in a qualitative synthesis, and 33 studies were included in a meta-analysis. Topical glyceryl trinitrate (GTN) reduced pain on day 7 (7 studies, 485 participants), with a mean difference and 95% confidence interval (MD, 95% CI) of -1.34 (-2.31; -0.37), I2 = 91%. Diltiazem reduced pain on day 3 on the VAS, and the MD was -2.75 (-398; -1.51) shown in five studies (n = 227). Botulinum toxin reduced pain on day 7, in four studies with 178 participants, MD -1.43 (-2.50; -0.35) I2 = 62%. The addition of Lateral Internal Sphincterotomy to haemorrhoidectomy reduced pain on day 2 in three studies with 275 participants, MD of -2.13 (-3.49; -0.77) I2 = 92%. The results were limited by high heterogeneity and risk of bias. CONCLUSION: Evidence suggests that lateral sphincterotomy, administration of botulinum toxin and the application of topical diltiazem or GTN can reduce post-operative pain after haemorrhoidectomy. Lateral sphincterotomy should not be routinely used due to the risk of incontinence.

Physiologically based pharmacokinetic modelling to predict drug-drug interactions for encorafenib. Part I. Model building, validation, and prospective predictions with enzyme inhibitors, inducers, and transporter inhibitors.

Encorafenib, a potent BRAF kinase inhibitor undergoes significant metabolism by CYP3A4 (83%) and CYP2C19 (16%) and also a substrate of P-glycoprotein (P-gp). Because of this, encorafenib possesses potential for enzyme-transporter related interactions. Clinically, its drug-drug interactions (DDIs) with CYP3A4 inhibitors (posaconazole, diltiazem) were reported and hence there is a necessity to study DDIs with multiple enzyme inhibitors, inducers, and P-gp inhibitors.USFDA recommended clinical CYP3A4, CYP2C19, P-gp inhibitors, CYP3A4 inducers were selected and prospective DDIs were simulated using physiologically based pharmacokinetic modelling (PBPK). Impact of dose (50 mg vs. 300 mg) and staggering of administrations (0-10 h) on the DDIs were predicted.PBPK models for encorafenib, perpetrators simulated PK parameters within twofold prediction error. Clinically reported DDIs with posaconazole and diltiazem were successfully predicted.CYP2C19 inhibitors did not result in significant DDI whereas strong CYP3A4 inhibitors resulted in DDI ratio up to 4.5. Combining CYP3A4, CYP2C19 inhibitors yielded DDI equivalent CYP3A4 alone. Strong CYP3A4 inducers yielded DDI ratio up to 0.3 and no impact of P-gp inhibitors on DDIs was observed. The DDIs were not impacted by dose and staggering of administration. Overall, this work indicated significance of PBPK modelling for evaluating clinical DDIs with enzymes, transporters and interplay.

The effect of serum calcium level on the success of diltiazem treatment: A retrospective cohort study.

INTRODUCTION: Diltiazem is an antiarrhythmic drug widely used in the treatment of atrial fibrillation (AFib) with rapid ventricular response (RVR). It reveals its effect by blocking L-type calcium channels. Thus, it inhibits the extracellular calcium influx into the cytosol. The relationship between serum calcium level and the efficacy of intravenous (IV) diltiazem used in the treatment of AFib with RVR has not been investigated in vivo. The aim of this study is to investigate the mentioned relationship. METHODS: This study was planned as a single-center retrospective study. The data of 349 patients who presented to the emergency department with AFib with RVR and treated with diltiazem were retrospectively analyzed. A patient was considered to have responded to diltiazem treatment if the existing heart rhythm returned to sinus rhythm, or the heart rate decreased below 100 beats/min, or the heart rate decreased >20% provided that it was below 120 beats/min. The ionized calcium levels were recorded. The relationship between serum calcium level and the success of diltiazem treatment was examined. RESULTS: Fifty five percent of the patients were female. The median age was 75 years. The rate of response to diltiazem treatment was 67.3%. The median of ionized calcium levels in the group which responded to diltiazem treatment (n = 235) was 1.14 mmol/L (IQR: 0.12), and the group which did not respond to diltiazem treatment (n = 114) was 1.11 mmol/L (IQR: 0.12) (p = 0.322). The patients were divided into three groups as low, normal, and high calcium levels according to the calcium reference levels determined by the hospital laboratory. The rate of response to diltiazem treatment was 61.4% in patients with low ionized calcium levels, 76.1% in patients with normal ionized calcium levels, and 40.0% in patients with high ionized calcium levels. The rate of response to diltiazem treatment was higher in patients with normal ionized calcium levels compared to patients with low or high ionized calcium levels (p = 0.004, p = 0.003). CONCLUSION: The success rate of diltiazem used in the treatment of AFib with RVR was highest in physiological calcium levels. The current study may provide the clinician with awareness about the consideration of serum ionized calcium levels when choosing drugs in patients with AFib with RVR.

Impact of intravenous calcium with diltiazem for atrial fibrillation/flutter in the emergency department.

OBJECTIVE: The purpose of this study was to evaluate the effect of early intravenous (IV) calcium on systolic blood pressure (SBP) when administered with IV diltiazem in subjects with atrial fibrillation (AF) or flutter (AFL) with rapid ventricular response (RVR) in the Emergency Department (ED). METHODS: This was a multicenter, retrospective cohort study that evaluated adults admitted to the ED with documented AF or AFL, heart rate (HR) > 120 bpm, SBP 90 to 140 mmHg, and received treatment with IV diltiazem for rate control. The primary outcome was the change in SBP 60 min (+/- 30 min) after initial IV diltiazem administration. Secondary outcomes included time to initial rate control (HR < 100 bpm), time to sustained rate control (HR < 100 bpm for 3 h), change in HR, rates of hypotension, bradycardia, hypercalcemia, and line extravasation within 24 h of initial diltiazem administration. RESULTS: There were 198 subjects in the diltiazem monotherapy group and 56 subjects in the diltiazem with calcium group meeting the inclusion criteria. The primary outcome, median change in SBP 60 min after initial IV diltiazem administration, was similar between groups (-2 mmHg vs -1.5 mmHg; p = 0.642), but this difference was not statistically significant. All secondary outcomes were found to be similar between groups. Although not statistically significant, hypotension occurred more often in the diltiazem with calcium group (20.2% vs 32.1%; p = 0.060) while bradycardia occurred more often in the diltiazem monotherapy group (4.5% vs 0%; p = 0.213). In terms of achieving rate control, the administration of calcium with diltiazem did not significantly change the time to initial rate control (1.4 h vs 1.8 h; p = 0.141) or time to sustained rate control (7.9 h vs 7.7 h; p = 0.570) compared to diltiazem alone. CONCLUSIONS: In the setting of AF/AFL with RVR, administration of IV calcium with IV diltiazem did not show a significant impact on clinical or safety outcomes compared to IV diltiazem monotherapy.

Acute rate control with metoprolol versus diltiazem in atrial fibrillation with heart failure with reduced ejection fraction.

OBJECTIVE: Compare heart rate control between parenteral metoprolol and diltiazem and identify safety outcomes in the acute management of atrial fibrillation (AFib) with rapid ventricular response (RVR) in patients with heart failure with reduced ejection fraction (HFrEF). METHODS: This retrospective, single-center, cohort study included adult patients with HFrEF who received intravenous (IV) metoprolol or diltiazem for AFib RVR in the emergency department (ED). The primary outcome was rate control defined as HR <100 bpm or a HR reduction ≥20% within 30 min of first dose administration. The secondary outcomes included rate control within 60 min and 120 min from first dose, need for repeat dosing, and disposition. Safety outcomes included hypotensive and bradycardic events. RESULTS: Out of 552 patients, 45 patients met the inclusion criteria with 15 in the metoprolol group and 30 in the diltiazem group. Using bootstrapping method, patients treated with metoprolol were equally able to reach the primary outcome as those treated with diltiazem (BCa 95% CI: 0.14, 4.31). Hypotensive and bradycardia events remained zero in both groups. CONCLUSION: Our study provides further evidence that short term use of diltiazem is likely as safe and effective as metoprolol in the acute management of HFrEF patients with AFib RVR and provides support for the use of non-dihydropyridine calcium channel blockers (non-DHP CCBs) in this patient population.

Potential Clinically Relevant Effects of Sialylation on Human Serum AAG-Drug Interactions Assessed by Isothermal Titration Calorimetry: Insight into Pharmacoglycomics?

Human serum alpha-1 acid glycoprotein is an acute-phase plasma protein involved in the binding and transport of many drugs, especially basic and lipophilic substances. It has been reported that the sialic acid groups that terminate the N-glycan chains of alpha-1 acid glycoprotein change in response to certain health conditions and may have a major impact on drug binding to alpha-1 acid glycoprotein. The interaction between native or desialylated alpha-1 acid glycoprotein and four representative drugs-clindamycin, diltiazem, lidocaine, and warfarin-was quantitatively evaluated using isothermal titration calorimetry. The calorimetry assay used here is a convenient and widely used approach to directly measure the amount of heat released or absorbed during the association processes of biomolecules in solution and to quantitatively estimate the thermodynamics of the interaction. The results showed that the binding of drugs with alpha-1 acid glycoprotein were enthalpy-driven exothermic interactions, and the binding affinity was in the range of 10-5-10-6 M. Desialylated alpha-1 acid glycoprotein showed significantly different binding with diltiazem, lidocaine, and warfarin compared with native alpha-1 acid glycoprotein, whereas clindamycin showed no significant difference. Therefore, a different degree of sialylation may result in different binding affinities, and the clinical significance of changes in sialylation or glycosylation of alpha-1 acid glycoprotein in general should not be neglected.

In Esophageal Squamous Cells From Eosinophilic Esophagitis Patients, Th2 Cytokines Increase Eotaxin-3 Secretion Through Effects on Intracellular Calcium and a Non-Gastric Proton Pump.

BACKGROUND & AIMS: In upper airway cells, T helper 2 cytokines that signal through interleukin-4 (IL-4) receptor-α have been shown to stimulate eotaxin-3 secretion via a nongastric proton pump (ngH+,K+ATPase). To seek novel targets for eosinophilic esophagitis (EoE) treatments, we evaluated ngH+,K+ATPase expression in EoE squamous cells, and explored molecular pathways involved in eotaxin-3 secretion by IL-4 receptor-α signaling. METHODS: ngH+,K+ATPase expression in EoE cells was evaluated by quantitative real-time polymerase chain reaction and Western blotting. IL-4-stimulated eotaxin-3 secretion was measured by enzyme-linked immunosorbent assay after treatment with omeprazole, SCH 28080 (potassium-competitive acid blocker), ethylene glycol-bis(ß-aminoethyl)-N,N,N',N'-tetraacetoxymethyl ester (calcium chelator), 2-aminoethoxydiphenyl borate (inhibitor of endoplasmic reticulum calcium release), verapamil, and diltiazem (L-type calcium channel inhibitors). Intracellular calcium transients were measured by Fluo-4 fluorescence. Key experiments were confirmed in EoE primary cells and in RNA sequencing datasets from mucosal biopsies of patients with EoE and controls. RESULTS: EoE cells expressed ngH+,K+ATPase messenger RNA and protein. Omeprazole and SCH 28080 decreased IL-4-stimulated eotaxin-3 secretion. IL-4 increased intracellular calcium transients, and IL-4-stimulated eotaxin-3 secretion was blocked by ethylene glycol-bis(ß-aminoethyl)-N,N,N',N'-tetraacetoxymethyl ester, 2-aminoethoxydiphenyl borate, verapamil, and diltiazem. The combination of omeprazole and verapamil suppressed IL-4-stimulated eotaxin-3 secretion more than either agent alone. EoE biopsies expressed higher ngH+,K+ATPase and exhibited more calcium signaling than controls. CONCLUSIONS: EoE cells express a nongastric proton pump that mediates T helper 2 cytokine-stimulated eotaxin-3 secretion. IL-4 induces calcium release from the endoplasmic reticulum and calcium entry via L-type calcium channels, increasing intracellular calcium that contributes to eotaxin-3 secretion by EoE cells. L-type calcium channel inhibitors block T helper 2 cytokine-stimulated eotaxin-3 secretion, suggesting a potential role for these agents in EoE treatment.

Structural basis of Klotho binding to VEGFR2 and TRPC1 and repurposing calcium channel blockers as TRPC1 antagonists for the treatment of age-related cardiac hypertrophy.

Cardiac hypertrophy results in the higher rate of heart failures among aged groups. Klotho is an anti-aging protein that is involved in the regulation of VEGF-mediated Ca2+ entry by direct interaction with Vascular endothelial growth factor receptor 2 (VEGFR2) and transient receptor potential canonical Ca2+ channel 1 (TRPC1). Here, in this study, through in silico analysis, we modeled TRPC1 3-dimensional structure and followed by its optimization, characterized the interaction pattern of TRPC1, Klotho and VEGFR2. Subsequent molecular dynamics (MD) simulation analysis revealed that Klotho-specific (P520-N630) region exhibited interaction with VEGFR2, while its C-terminal region (I822-A931) demonstrated binding to the 3rd extracellular loop of TRPC1 that is adjacent to pore region. Through TRPC1 homotetramer formation, the residues in the periphery of pore region were carefully evaluated. In order to scrutinize known Ca2+ channel blockers for their ability to bind at the pore region of TRPC1, 31 known compounds were tested through docking runs and three hits, named as diltiazem impurity B (b3), diltiazem (b5) and felodipine (b6) were selected for detailed binding analysis through MD runs. Evidently, inhibitor-bound TRPC1 pore area was more constricted (8.6 Å2, 25.1 Å2 and 18.8 Å2, respectively) than apo-TRPC1 (60 Å2). These findings suggest that Ca+2 channel blockers may serve as promising agents to impair the TRPC1 functional store-operated calcium channel (SOCC) activity in the old patients lacking Klotho expression. Thus, pore region of homotetrameric TRPC1 may be blocked via repurposing of known Ca+2 blockers to antagonize TRPC signaling for the treatment of cardiac hypertrophy.