Clinical pharmacokinetics of amiodarone

The antiarrhythmic drugs amiodarone and dronedarone inhibit intoxication of cells with pertussis toxin

Pertussis toxin (PT) is a virulent factor produced by Bordetella pertussis, the causative agent of whooping cough. PT exerts its pathogenic effects by ADP-ribosylating heterotrimeric G proteins, disrupting cellular signaling pathways. Here, we investigate the potential of two antiarrhythmic drugs, amiodarone and dronedarone, in mitigating PT-induced cellular intoxication. After binding to cells, PT is endocytosed, transported from the Golgi to the endoplasmic reticulum where the enzyme subunit PTS1 is released from the transport subunit of PT. PTS1 is translocated into the cytosol where it ADP-ribosylates inhibitory α-subunit of G-protein coupled receptors (Gαi). We showed that amiodarone and dronedarone protected CHO cells and human A549 cells from PT-intoxication by analyzing the ADP-ribosylation status of Gαi. Amiodarone had no effect on PT binding to cells or in vitro enzyme activity of PTS1 but reduced the signal of PTS1 in the cell suggesting that amiodarone interferes with intracellular transport of PTS1. Moreover, dronedarone mitigated the PT-mediated effect on cAMP signaling in a cell-based bioassay. Taken together, our findings underscore the inhibitory effects of amiodarone and dronedarone on PT-induced cellular intoxication, providing valuable insights into drug repurposing for infectious disease management.

Preclinical evaluation of combined therapy with amiodarone and low-dose benznidazole in a mouse model of chronic Trypanosoma cruzi infection

Chagasic chronic cardiomyopathy (CCC) is the primary clinical manifestation of Chagas disease (CD), caused by Trypanosoma cruzi. Current therapeutic options for CD are limited to benznidazole (Bz) and nifurtimox. Amiodarone (AMD) has emerged as most effective drug for treating the arrhythmic form of CCC. To address the effects of Bz and AMD we used a preclinical model of CCC. Female C57BL/6 mice were infected with T. cruzi and subjected to oral treatment for 30 consecutive days, either as monotherapy or in combination. AMD in monotherapy decreased the prolonged QTc interval, the incidence of atrioventricular conduction disorders and cardiac hypertrophy. However, AMD monotherapy did not impact parasitemia, parasite load, TNF concentration and production of reactive oxygen species (ROS) in cardiac tissue. Alike Bz therapy, the combination of Bz and AMD (Bz/AMD), improved cardiac electric abnormalities detected T. cruzi-infected mice such as decrease in heart rates, enlargement of PR and QTc intervals and increased incidence of atrioventricular block and sinus arrhythmia. Further, Bz/AMD therapy ameliorated the ventricular function and reduced parasite burden in the cardiac tissue and parasitemia to a degree comparable to Bz monotherapy. Importantly, Bz/AMD treatment efficiently reduced TNF concentration in the cardiac tissue and plasma and had beneficial effects on immunological abnormalities. Moreover, in the cardiac tissue Bz/AMD therapy reduced fibronectin and collagen deposition, mitochondrial damage and production of ROS, and improved sarcomeric and gap junction integrity. Our study underlines the potential of the Bz/AMD therapy, as we have shown that combination increased efficacy in the treatment of CCC.

Selected widely prescribed pharmaceuticals: toxicity of the drugs and the products of their photochemical degradation to aquatic organisms

Cholesterol-lowering drugs, antidiabetics, antiarrhythmics, antidepressants, and antibiotics belong to the most prescribed drugs worldwide. Because of the manufacture, excretion, and improper disposal of leftover drugs, the drugs enter waste waters and, subsequently, surface waters. They have been detected in surface waters all over the world, from concentrations of ng/l to concentrations several orders of magnitude higher. Since pharmaceuticals are designed to be both biologically and chemically stable, photochemical degradation by sun radiation represents a way of transformation in the natural environment. This review provides a survey of how selected drugs of the above-mentioned classes affect aquatic organisms of different trophic level. The emphasis is on the harmful effects of phototransformation products, an area of scientific investigation that has only attracted attention in the past few years, revealing the surprising fact that products of photochemical degradation might be even more toxic to aquatic organisms than the parent drugs.

Junctional Ectopic Tachycardia Caused by Junctophilin-2 Expression Silencing Is Selectively Sensitive to Ryanodine Receptor Blockade

Junctional ectopic tachycardia (JET) is a potentially fatal cardiac arrhythmia. Hcn4:shJph2 mice serve as a model of nodal arrhythmias driven by ryanodine type 2 receptor (RyR2)-mediated Ca2+ leak. EL20 is a small molecule that blocks RyR2 Ca2+ leak. In a novel in vivo model of JET, Hcn4:shJph2 mice demonstrated rapid conversion of JET to sinus rhythm with infusion of EL20. Primary atrioventricular nodal cells demonstrated increased Ca2+ transient oscillation frequency and increased RyR2-mediated stored Ca2+ leak which was normalized by EL20. EL20 was found to be rapidly degraded in mouse and human plasma, making it a potential novel therapy for JET.

Exploring the inhibitory potential of the antiarrhythmic drug amiodarone against Clostridioides difficile toxins TcdA and TcdB

The intestinal pathogen Clostridioides difficile is the leading cause of antibiotic-associated diarrhea and pseudomembranous colitis in humans. The symptoms of C. difficile-associated diseases (CDADs) are directly associated with the pathogen's toxins TcdA and TcdB, which enter host cells and inactivate Rho and/or Ras GTPases by glucosylation. Membrane cholesterol is crucial during the intoxication process of TcdA and TcdB, and likely involved during pore formation of both toxins in endosomal membranes, a key step after cellular uptake for the translocation of the glucosyltransferase domain of both toxins from endosomes into the host cell cytosol. The licensed drug amiodarone, a multichannel blocker commonly used in the treatment of cardiac dysrhythmias, is also capable of inhibiting endosomal acidification and, as shown recently, cholesterol biosynthesis. Thus, we were keen to investigate in vitro with cultured cells and human intestinal organoids, whether amiodarone preincubation protects from TcdA and/or TcdB intoxication. Amiodarone conferred protection against both toxins independently and in combination as well as against toxin variants from the clinically relevant, epidemic C. difficile strain NAP1/027. Further mechanistic studies suggested that amiodarone's mode-of-inhibition involves also interference with the translocation pore of both toxins. Our study opens the possibility of repurposing the licensed drug amiodarone as a novel pan-variant antitoxin therapeutic in the context of CDADs.

Amiodarone but not propafenone impairs bioenergetics and autophagy of human myocardial cells

Cardiac and extra-cardiac side effects of common antiarrhythmic agents might be related to drug-induced mitochondrial dysfunction. Supratherapeutic doses of amiodarone have been shown to impair mitochondria in animal studies, whilst influence of propafenone on cellular bioenergetics is unknown. We aimed to assess effects of protracted exposure to pharmacologically relevant doses of amiodarone and propafenone on cellular bioenergetics and mitochondrial biology of human and mouse cardiomyocytes. In this study, HL-1 mouse atrial cardiomyocytes and primary human cardiomyocytes derived from the ventricles of the adult heart were exposed to 2 and 7 μg/mL of either amiodarone or propafenone. After 24 h, extracellular flux analysis and confocal laser scanning microscopy were used to measure mitochondrial functions. Autophagy was assessed by western blots and live-cell imaging of lysosomes. In human cardiomyocytes, amiodarone significantly reduced mitochondrial membrane potential and ATP production, in association with an inhibition of fatty acid oxidation and impaired complex I- and II-linked respiration in the electron transport chain. Expectedly, this led to increased anaerobic glycolysis. Amiodarone increased the production of reactive oxygen species and autophagy was also markedly affected. In contrast, propafenone-exposed cardiomyocytes did not exert any impairment of cellular bioenergetics. Similar changes after amiodarone treatment were observed during identical experiments performed on HL-1 mouse cardiomyocytes, suggesting a comparable pharmacodynamics of amiodarone among mammalian species. In conclusion, amiodarone but not propafenone in near-therapeutic concentrations causes a pattern of mitochondrial dysfunction with affected autophagy and metabolic switch from oxidative metabolism to anaerobic glycolysis in human cardiomyocytes.

Single and joint toxic effects of thyroid hormone, levothyroxine, and amiodarone on embryo-larval stages of zebrafish (Danio rerio)

This study evaluates single and joint endocrine disruptor toxicities of thyroid hormone, levothyroxine, and amiodarone in the embryo-larval stages of Danio rerio. Single toxicity experiments were carried out in concentrations based on the environmental concentration and increasing concentrations of 10, 100, and 1000 times the environmental concentration. Joint toxicity experiments evaluated the combined effects of these compounds. Toxic effects were examined during zebrafish embryonic development, and the parameters analyzed were apical sublethal, teratogenicity, mortality endpoints, and morphometry. Thyroid hormone exhibited the highest toxicity. However, the results showed that the environmental concentrations for all 3 compounds had low risk in relation to the parameters studied, such as teratogenic effects and morphometry. The larvae were more affected than embryos, where embryos needed higher concentrations in all experiments, possibly due to the absence of the chorion. The same type of effects were observed in the joint toxicity test, except that a possible antagonistic effect was detected. However, high concentrations showed stronger effects of these toxic compounds on fish development.

Managing postoperative atrial fibrillation after open-heart surgery using transdermal β1 blockers

BACKGROUND

Postoperative atrial fibrillation (POAF) after open-heart surgery is a non-negligible complication. We aimed to describe the efficacy of a transdermal patch of bisoprolol for managing POAF and flutter in thoracic surgical procedures.

METHODS

We analyzed the data of 384 patients who underwent open-heart surgery at our hospital and received oral bisoprolol to prevent POAF. Among them, 65 patients (16.9%) also received a 4-mg transdermal patch of bisoprolol to control the heart rate due to POAF. We applied the bisoprolol transdermal patch when the heart rate was > 80 bpm and removed it at ≤ 60 bpm; an additional patch was applied when the heart rate was > 140 bpm. Heparin calcium injections were administered twice daily for anticoagulation between 2 and 6 days postoperatively.

RESULTS

The average number of prescriptions for transdermal patches of bisoprolol during hospitalization was 1.8 ± 1.1 (1-5). The median first prescription date was on postoperative day 2 (range: days 0-37). Sinus rhythm recovered within 24 h in 18 patients (27.7%). Eight patients (12.3%) were switched to continuous landiolol infusion because of persistent tachycardia. In three patients, the transdermal patch was removed owing to severe bradycardia. Fifteen patients experienced persistent atrial fibrillation and were treated with electrical cardioversion during hospitalization. We did not observe any serious complications that could be directly attributed to bisoprolol transdermal patch use.

CONCLUSIONS

Single-use bisoprolol transdermal patch may help control the heart rate during the initial treatment of POAF after open-heart surgery.

In Vitro-In Vivo Extrapolation by Physiologically Based Kinetic Modeling: Experience With Three Case Studies and Lessons Learned

Physiologically based kinetic (PBK) modeling has been increasingly used since the beginning of the 21st century to support dose selection to be used in preclinical and clinical safety studies in the pharmaceutical sector. For chemical safety assessment, the use of PBK has also found interest, however, to a smaller extent, although an internationally agreed document was published already in 2010 (IPCS/WHO), but at that time, PBK modeling was based mostly on in vivo data as the example in the IPCS/WHO document indicates. Recently, the OECD has published a guidance document which set standards on how to characterize, validate, and report PBK models for regulatory purposes. In the past few years, we gained experience on using in vitro data for performing quantitative in vitro–in vivo extrapolation (QIVIVE), in which biokinetic data play a crucial role to obtain a realistic estimation of human exposure. In addition, pharmaco-/toxicodynamic aspects have been introduced into the approach. Here, three examples with different drugs/chemicals are described, in which different approaches have been applied. The lessons we learned from the exercise are as follows: 1) in vitro conditions should be considered and compared to the in vivo situation, particularly for protein binding; 2) in vitro inhibition of metabolizing enzymes by the formed metabolites should be taken into consideration; and 3) it is important to extrapolate from the in vitro measured intracellular concentration and not from the nominal concentration to the tissue/organ concentration to come up with an appropriate QIVIVE for the relevant adverse effects.

Population Pharmacokinetic Model of Amiodarone and N-Desethylamiodarone Focusing on Glucocorticoid and Inflammation

Some population pharmacokinetic models for amiodarone (AMD) did not incorporate N-desethylamiodarone (DEA) concentration. Glucocorticoids activate CYP3A4 activity, metabolizing AMD. In contrast, CYP3A4 activity may decrease under inflammation conditions. However, direct evidence for the role of glucocorticoid or inflammation on the pharmacokinetics of AMD and DEA is lacking. The pilot study aimed to address this gap using a population pharmacokinetic analysis of AMD and DEA. A retrospective cohort observational study in adult patients who underwent AMD treatment with trough concentration measurement was conducted at Tokyo Women's Medical University, Medical Center East from June 2015 to March 2019. Both structural models of AMD and DEA applied 1-compartment models, which included significant covariates using a stepwise forward selection and backward elimination method. The eligible 81 patients (C-reactive protein level: 0.26 [interquartile range; 0.09-1.92] mg/dL) had a total of 408 trough concentrations for both AMD and DEA. The median trough concentrations were 0.49 [0.31-0.81] µg/mL for AMD and 0.43 [0.28-0.71] µg/mL for DEA during a median follow-up period of 446 [147-1059] d. Three patients received low-dose oral glucocorticoid. The final model identified that AMD clearance was 7.9 L/h, and the apparent DEA clearance was 10.3 L/h. Co-administered glucocorticoids lowered apparent DEA clearance by 35%. These results indicate that co-administered glucocorticoids may increase DEA concentrations in patients without severe inflammation.

Drug-Drug Interactions of Direct Oral Anticoagulants (DOACs): From Pharmacological to Clinical Practice

The direct oral anticoagulants (DOACs), dabigatran, rivaroxaban, apixaban, and edoxaban, are becoming the most commonly prescribed drugs for preventing ischemic stroke in patients with non-valvular atrial fibrillation (NVAF) and for the treatment and prevention of venous thromboembolism (VTE). Rivaroxaban was also recently approved for the treatment of patients with a recent acute coronary syndrome (ACS). Their use demonstrated to have a favorable risk-benefit profile, with significant reductions in stroke, intracranial hemorrhage, and mortality compared to warfarin, but with increased gastrointestinal bleeding. Nevertheless, their safety profile is compromised in multimorbidity patients requiring contemporary administration of several drugs. Comorbidity and polypharmacy have a high prevalence in elderly patients, who are also more susceptible to bleeding events. The combination of multiple treatments can cause relevant drug–drug interactions (DDIs) by affecting the exposure or the pharmacological activities of DOACs. Although important differences of the pharmacokinetic (PK) properties can be observed between DOACs, all of them are substrate of P-glycoprotein (P-gp) and thus may interact with strong inducers or inhibitors of this drug transporter. On the contrary, rivaroxaban and, to a lower extent, apixaban, are also susceptible to drugs altering the cytochrome P450 isoenzyme (CYP) activities. In the present review, we summarize the potential DDI of DOACs with several classes of drugs that have been reported or have characteristics that may predict clinically significant DDIs when administered together with DOACs. Possible strategies, including dosage reduction, avoiding concomitant administration, or different time of treatment, will be also discussed to reduce the incidence of DDI with DOACs. Considering the available data from specific clinical trials or registries analysis, the use of DOACs is associated with fewer clinically relevant DDIs than warfarin, and their use represents an acceptable clinical choice. Nevertheless, DDIs can be significant in certain patient conditions so a careful evaluation should be made before prescribing a specific DOAC.

Drug Interactions Affecting Antiarrhythmic Drug Use

Antiarrhythmic drugs (AAD) play an important role in the management of arrhythmias. Drug interactions involving AAD are common in clinical practice. As AADs have a narrow therapeutic window, both pharmacokinetic as well as pharmacodynamic interactions involving AAD can result in serious adverse drug reactions ranging from arrhythmia recurrence, failure of device-based therapy, and heart failure, to death. Pharmacokinetic drug interactions frequently involve the inhibition of key metabolic pathways, resulting in accumulation of a substrate drug. Additionally, over the past 2 decades, the P-gp (permeability glycoprotein) has been increasingly cited as a significant source of drug interactions. Pharmacodynamic drug interactions involving AADs commonly involve additive QT prolongation. Amiodarone, quinidine, and dofetilide are AADs with numerous and clinically significant drug interactions. Recent studies have also demonstrated increased morbidity and mortality with the use of digoxin and other AAD which interact with P-gp. QT prolongation is an important pharmacodynamic interaction involving mainly Vaughan-Williams class III AAD as many commonly used drug classes, such as macrolide antibiotics, fluoroquinolone antibiotics, antipsychotics, and antiemetics prolong the QT interval. Whenever possible, serious drug-drug interactions involving AAD should be avoided. If unavoidable, patients will require closer monitoring and the concomitant use of interacting agents should be minimized. Increasing awareness of drug interactions among clinicians will significantly improve patient safety for patients with arrhythmias.

Comparative analysis of in vivo and in silico toxicity evaluation of the organoiodine compounds towards D.magna using multivariate chemometric approach: A study on the example of amiodarone phototransformation products

In the present study the photochemical fate of organoiodine compound - amiodarone was performed. The drug turned out to be highly susceptible to UV-Vis irradiation, especially in the presence of humic substances and organic matrix. Qualitative LC-MS analysis revealed formation of twelve - mainly previously unreported - transformation products (TPs). Four major TPs were submitted to the toxicity analysis with the use of D. magna. All of the tested TPs presented higher toxic potential than the parent compound. The phenolic TPs were approximately 100 times more toxic than amiodarone. Toxic properties of the major TPs resulted in steadily increasing toxic potential of the photo-generated mixture over the time of irradiation. Moreover, the experimental toxicity data, concerning the TPs, were compared with results estimated by 6 in silico models with the use of a multivariate chemometric analysis. The results showed that the applied computational methods were able neither to correctly predict toxic properties of the studied compounds, nor the trends in change of their toxic parameters. Additional validation of in silico models ability to predict toxicity of iodinated organic compounds showed that the studied computational methods do not present sufficient prediction ability. Therefore their estimations concerning organoiodines should be verified using experimental tests.

Increased serum amiodarone concentration in hypertriglyceridemic patients: Effects of drug distribution to serum lipoproteins

Amiodarone and its main metabolite, desethylamiodarone (DEA), are highly distributed to serum lipoproteins such as very‐low‐density lipoprotein (VLDL) and low‐density lipoprotein (LDL), which are the carriers of triglyceride and cholesterol. This study aimed to investigate the association of serum concentrations of amiodarone and DEA with the levels of serum lipids in terms of drug distribution to lipoprotein fractions in patients with hyperlipidemia. Total serum concentrations of amiodarone and DEA were examined in 116 patients receiving amiodarone for tachyarrhythmias. The concentration‐to‐dose (C/D) ratio of amiodarone positively correlated with the level of serum triglyceride (r_s = 0.541, p < 0.001) and was higher in the hypertriglyceridemic state than in normotriglyceridemic state (479 ± 211 vs. 320 ± 161, p < 0.001). No correlation was found between the C/D ratio of DEA and serum triglyceride levels (r_s = 0.272), although higher values were observed in the hypertriglyceridemic state (322 ± 125 vs. 285 ± 143, p < 0.001). In the hypertriglyceridemic state, the distribution of amiodarone increased in LDL/VLDL fraction and decreased in high‐density lipoprotein and albumin fractions. The ratio of serum amiodarone to serum DEA, a metabolic ratio of amiodarone, positively correlated with serum triglyceride levels (r_s = 0.572, p < 0.001) and was higher in the hypertriglyceridemic state, suggesting that amiodarone metabolism decreased in hyperlipidemia. The results of this study reveal that serum concentrations of amiodarone increase in the hypertriglyceridemic state through the increased lipoprotein‐binding and decreased metabolism of amiodarone.

The effects of amiodarone on thyroid function in pediatric and adolescent patients

PURPOSE OF REVIEW

Amiodarone-induced thyroid dysfunction is well established. The present review discusses recent literature related to the effects of amiodarone on the thyroid gland and thyroid function in pediatrics.

RECENT FINDINGS

Current guidelines in adults treated with amiodarone recommend baseline thyroid function testing followed by initiation of thyroid hormone monitoring after 3 months on therapy. Two retrospective studies to evaluate amiodarone-induced thyroid dysfunction in children and young adults reveal thyroid dysfunction as soon as 2 weeks after amiodarone initiation with a greater percentage of pediatric patients developing amiodarone-induced hypothyroidism rather than thyrotoxicosis. Although additional studies are needed to determine if AIH is associated with negative impact on growth and neurocognitive development, what is clear is that in both adults and pediatrics, there is low compliance with recommended side effect-monitoring guidelines.

SUMMARY

Pediatric patients are at similarly high risk to develop amiodarone-induced thyroid dysfunction as are adults. It is hoped that through improved education of providers and patients further research into the incidence, the potential risks of amiodarone therapy and the potential benefits of thyroid hormone replacement therapy in patients with AIH will be investigated and reported.

Antiparasitic Properties of Cardiovascular Agents against Human Intravascular Parasite Schistosoma mansoni

The intravascular parasitic worm Schistosoma mansoni is a causative agent of schistosomiasis, a disease of great global public health significance. Praziquantel is the only drug available to treat schistosomiasis and there is an urgent demand for new anthelmintic agents. Adopting a phenotypic drug screening strategy, here, we evaluated the antiparasitic properties of 46 commercially available cardiovascular drugs against S. mansoni. From these screenings, we found that amiodarone, telmisartan, propafenone, methyldopa, and doxazosin affected the viability of schistosomes in vitro, with effective concentrations of 50% (EC₅₀) and 90% (EC₉₀) values ranging from 8 to 50 µM. These results were further supported by scanning electron microscopy analysis. Subsequently, the most effective drug (amiodarone) was further tested in a murine model of schistosomiasis for both early and chronic S. mansoni infections using a single oral dose of 400 mg/kg or 100 mg/kg daily for five consecutive days. Amiodarone had a low efficacy in chronic infection, with the worm and egg burden reduction ranging from 10 to 30%. In contrast, amiodarone caused a significant reduction in worm and egg burden in early infection (>50%). Comparatively, treatment with amiodarone is more effective in early infection than praziquantel, demonstrating the potential role of this cardiovascular drug as an antischistosomal agent.

Pharmacokinetic Disposition of Amiodarone When Given with an Intralipid Rescue Strategy

While the antiarrhythmic drug amiodarone is commonly used in clinical practice, it has a narrow therapeutic index that can lead to acute overdose. One proposed method to deal with this toxicity is lipid emulsion therapy, which may potentially quench the free amiodarone in blood and prevent its further distribution to target organs and tissues. In this study, we utilize an established swine model to examine the effects of Intralipid™ (IL) administration for acute amiodarone toxicity. A total of 14 pigs received an overdose of intravenous amiodarone. After twenty minutes, half of the pigs (n = 7) received IL while the control group (n = 7) received normal saline. Serum concentrations of amiodarone were then analyzed using a validated high-performance liquid chromatography (HPLC) method. Noncompartmental pharmacokinetic analyses were performed on the observed concentrations. There were no statistical differences in the area under the concentration time curve (6 h) or clearance, but there was a difference in the half-life between the two groups (3.12 vs. 0.85 h, p = 0.01). The administration of IL did not statistically change the overall exposure of amiodarone in the blood in the first 6 h; however, trends toward prolonged blood retention in the IL group were seen.

Amiodarone Extraction by the Extracorporeal Membrane Oxygenation Circuit

Amiodarone is an anti-arrhythmic agent that is frequently used to treat tachycardias in critically ill adults and children. Because of physicochemical properties of amiodarone, extracorporeal membrane oxygenation (ECMO) circuits are expected to extract amiodarone from circulation, increasing the risk of therapeutic failure. The present study seeks to determine amiodarone extraction by the ECMO circuit. Amiodarone was administered to three ex vivo circuit configurations (n = 3 per configuration) to determine the effect of each circuit component on drug extraction. The circuits were primed with human blood; standard amiodarone doses were administered; and serial samples were collected over 24 hours. Additional circuits were primed with crystalloid fluid to analyze the effect of blood on extraction and to investigate circuit saturation by drug. The crystalloid circuits were dosed multiple times over 72 hours, including a massive dose at 48 hours. For both setups, the flow was set to 1 L/min. Drug was added to separate tubes containing the prime solution to serve as controls. Drug concentrations were quantified with a validated assay, and drug recovery was calculated for each sample. Mean recovery for the circuits and controls were compared to correct for drug degradation over time. Amiodarone was heavily extracted by all ECMO circuit configurations. Eight hours after dosing, mean recovery in the blood prime circuits was 13.5-22.1%. In the crystalloid prime circuits, drug recovery decreased even more rapidly, with a mean recovery of 22.0% at 30 minutes. Similarly, drug recovery decreased more quickly in the crystalloid prime controls than in the blood prime controls. Saturation was not achieved in the crystalloid prime circuits, as final amiodarone concentrations were at the lower limit of quantification. The results suggest that amiodarone is rapidly extracted by the ECMO circuit and that saturation is not achieved by standard doses. In vivo circuit extraction may cause decreased drug exposure.

Metabolic N-Dealkylation and N-Oxidation as Elucidators of the Role of Alkylamino Moieties in Drugs Acting at Various Receptors

Metabolic reactions that occur at alkylamino moieties may provide insight into the roles of these moieties when they are parts of drug molecules that act at different receptors. N-dealkylation of N,N-dialkylamino moieties has been associated with retaining, attenuation or loss of pharmacologic activities of metabolites compared to their parent drugs. Further, N-dealkylation has resulted in clinically used drugs, activation of prodrugs, change of receptor selectivity, and providing potential for developing fully-fledged drugs. While both secondary and tertiary alkylamino moieties (open chain aliphatic or heterocyclic) are metabolized by CYP450 isozymes oxidative N-dealkylation, only tertiary alkylamino moieties are subject to metabolic N-oxidation by Flavin-containing monooxygenase (FMO) to give N-oxide products. In this review, two aspects will be examined after surveying the metabolism of representative alkylamino-moieties-containing drugs that act at various receptors (i) the pharmacologic activities and relevant physicochemical properties (basicity and polarity) of the metabolites with respect to their parent drugs and (ii) the role of alkylamino moieties on the molecular docking of drugs in receptors. Such information is illuminative in structure-based drug design considering that fully-fledged metabolite drugs and metabolite prodrugs have been, respectively, developed from N-desalkyl and N-oxide metabolites.

Amiodarone is associated with increased short-term mortality in elderly atrial fibrillation patients with preserved ejection fraction

PURPOSE

Amiodarone is commonly used in atrial fibrillation (AF). Long-term use of amiodarone is associated with significant toxicities especially in elderly patients. However, in the short term after hospitalization of AF, it remains uncertain whether the use of amiodarone will increase mortality. We aim to investigate whether Amiodarone affects short-term mortality in elderly patients after hospitalization for atrial fibrillation.

METHODS

We conducted a single-center retrospective cohort study including patients (Age > = 60 years old) who were hospitalized between 07/01/2004 and 06/30/2019 with primary diagnosis of AF and left ventricular ejection fraction (LVEF) > = 50%. Patients who were prescribed amiodarone during hospitalization but not before hospitalization are classified into Amiodarone group (341 patients). Patients who were not prescribed amiodarone are classified into non-amiodarone group (2171 patients). Propensity score matching was performed with 1:1 nearest-neighbor matching of Amiodarone group and Non-amiodarone group based on baseline variables. Univariate and Multivariate logistic regression were used to calculate the odds ratio of amiodarone use on in-hospital mortality, and multivariate cox regression was adopted to calculate the hazard ratio of amiodarone use on 100-day mortality.

RESULTS

Patients' baseline demographic and clinical characteristics were well matched in both groups. Both univariate and multivariate logistic regression showed amiodarone group had higher in-hospital mortality (OR 10.27, p = 0.0268; 16.50, p = 0.0171) than non-amiodarone group and multivariate Cox regression suggested increased 100-day all-cause mortality (HR 2.34, p = 0.022).

CONCLUSION

Amiodarone use in elderly patients with preserved ejection fraction is associated with increased in-hospital and 100-day all-cause mortality after hospitalization for AF.

Challenges in the Management of Atrial Fibrillation With Subclinical Hyperthyroidism

Subclinical thyroid disorders have a high prevalence among older individuals and women. Subclinical hypothyroidism is diagnosed by elevated serum levels of thyroid-stimulating hormone (TSH) with thyroxine levels within the reference range, and subclinical hyperthyroidism is diagnosed by low TSH in conjunction with thyroxine and triiodothyronine levels within reference ranges. Atrial fibrillation is the most commonly diagnosed cardiac arrhythmia and has been associated with an increased risk of mortality, heart failure, stroke, and depression. Mechanistic data from animal and human physiology studies as well as observational data in humans support an association of subclinical hyperthyroidism with atrial fibrillation. Guidelines recommend the measurement of TSH in the evaluation of new-onset atrial fibrillation. All patients with overt hyperthyroidism should be treated, and treatment of subclinical hyperthyroidism should be considered in patients older than 65 years with TSH < 0.4 mlU/L, or in younger patients with TSH < 0.1 mlU/L. Guidelines also recommend screening for AF in patients with known hyperthyroidism. Wearable devices that measure the heart electrical activity continuously may be a novel strategy to detect atrial fibrillation in patients at risk. In this review, we explore the interplay between thyroid hormones and atrial fibrillation, management controversies in subclinical hyperthyroidism, and potential strategies to improve the management of atrial fibrillation in patients with subclinical hyperthyroidism.

Approach to the Patient: Perioperative Management of the Patient with Pheochromocytoma or Sympathetic Paraganglioma

Pheochromocytomas and sympathetic paraganglioma (PPGL) are rare chromaffin cell tumors originating in the adrenal medulla and sympathetic paraganglia, respectively, which share the capacity to synthesize and release catecholamines. The incidence of PPGL has increased in recent years. Surgical resection is the only curative treatment for PPGL. Management of patients with PPGL is complex and should be done by a specialized multidisciplinary team in centers with broad expertise. Surgical resection of a PPGL is a high-risk procedure for which optimal pretreatment with antihypertensive drugs is required in combination with state-of-the-art surgical procedures and anesthesiological techniques. In this article we discuss the underlying evidence and the pros and cons of presurgical medical preparation. Finally, the areas of uncertainty and controversies in this field are addressed.

Atrial Fibrillation in COVID-19: From Epidemiological Association to Pharmacological Implications

Coronavirus disease 2019 (COVID-19) outbreak is a public health emergency of international concerns because of a highly pathogenic human coronavirus (HCoV), actually named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Despite much emerging data about the epidemiological association between cardiovascular diseases and COVID-19, little is still known about atrial fibrillation and its optimal management in this clinical contest. The aim of our review is to describe the pharmacological interactions between cardiovascular drugs more commonly used in atrial fibrillation management and experimental COVID-19 therapies, based on EU and US summaries of product characteristics.

Combined amiodarone and digitalis therapy before heart transplantation is associated with increased post-transplant mortality

Aims

Amiodarone and digitalis are frequently used drugs in patients with heart failure. Both have separately been linked to reduced post‐transplant survival, but their combined impact on mortality after HTX remains uncertain. This study investigated the effects of combined amiodarone and digitalis use before HTX on post‐transplant outcomes.

Methods and results

This registry study analysed 600 patients receiving HTX at Heidelberg Heart Center between 1989 and 2016. Patients were stratified by amiodarone and digitalis use before HTX. Analysis included patient characteristics, medication, echocardiographic features, heart rates, permanent pacemaker implantation, atrial fibrillation, and post‐transplant survival including causes of death. One hundred eighteen patients received amiodarone before HTX (19.7%), hereof 67 patients with digitalis (56.8%) and 51 patients without digitalis before HTX (43.2%). Patients with and without amiodarone before HTX showed a similar 1 year post‐transplant survival (72.0% vs. 78.4%, P = 0.11), but patients with combined amiodarone and digitalis before HTX had a worse 1 year post‐transplant survival (64.2%, P = 0.01), along with a higher percentage of death due to transplant failure (P = 0.03). Echocardiographic analysis of these patients showed a higher percentage of an enlarged right ventricle (P = 0.02), left atrium (P = 0.02), left ventricle (P = 0.03), and a higher rate of reduced left ventricular ejection fraction (P = 0.03). Multivariate analysis indicated combined amiodarone and digitalis use before HTX as a significant risk factor for 1 year mortality after HTX (hazard ratio: 1.69; 95% confidence interval: 1.02–2.77; P = 0.04).

Conclusions

Combined pre‐transplant amiodarone and digitalis therapy is associated with increased post‐transplant mortality.

Iodine accumulation of the liver in patients treated with amiodarone can be unmasked using material decomposition from multiphase spectral-detector CT

Amiodarone accumulates in the liver, where it increases x-ray attenuation due to its iodine content. We evaluated liver attenuation in patients treated and not treated with amiodarone using true-non-contrast (TNC) and virtual-non-contrast (VNC) images acquired with spectral-detector-CT (SDCT). 142 patients, of which 21 have been treated with amiodarone, receiving SDCT-examinations (unenhanced-chest CT [TNC], CT-angiography of chest and abdomen [CTA-Chest, CTA-Abdomen]) were included. TNC, CTA-Chest, CTA-Abdomen, and corresponding VNC-images (VNC-Chest, VNC-Abdomen) were reconstructed. Liver-attenuation-index (LAI) was calculated as difference between liver- and spleen-attenuation. Liver-attenuation and LAI derived from TNC-images of patients receiving amiodarone were higher. Contrary to TNC, liver-attenuation and LAI were not higher in amiodarone patients in VNC-Chest and in VNC-Abdomen. To verify these initial results, a phantom scan was performed and an additional patient cohort included, both confirming that VNC is viable of accurately subtracting iodine of hepatic amiodarone-deposits. This might help to monitor liver-attenuation more accurately and thereby detect liver steatosis as a sign of liver damage earlier as well as to verify amiodarone accumulation in the liver.

Blinded In Silico Drug Trial Reveals the Minimum Set of Ion Channels for Torsades de Pointes Risk Assessment

Torsades de Pointes (TdP) is a type of ventricular arrhythmia which could be observed as an unwanted drug-induced cardiac side effect, and it is associated with repolarization abnormalities in single cells. The pharmacological evaluations of TdP risk in previous years mainly focused on the hERG channel due to its vital role in the repolarization of cardiomyocytes. However, only considering drug effects on hERG led to false positive predictions since the drug action on other ion channels can also have crucial regulatory effects on repolarization. To address the limitation of only evaluating hERG, the Comprehensive in Vitro Proarrhythmia Assay initiative has proposed to systematically integrate drug effects on multiple ion channels into in silico drug trial to improve TdP risk assessment. It is not clear how many ion channels are sufficient for reliable TdP risk predictions, and whether differences in IC₅₀ and Hill coefficient values from independent sources can lead to divergent in silico prediction outcomes. The rationale of this work is to investigate the above two questions using a computationally efficient population of human ventricular cells optimized to favor repolarization abnormality. Our blinded results based on two independent data sources confirm that simulations with the optimized population of human ventricular cell models enable efficient in silico drug screening, and also provide direct observation and mechanistic analysis of repolarization abnormality. Our results show that 1) the minimum set of ion channels required for reliable TdP risk predictions are Nav1.5 (peak), Cav1.2, and hERG; 2) for drugs with multiple ion channel blockage effects, moderate IC₅₀ variations combined with variable Hill coefficients can affect the accuracy of in silico predictions.

Amiodarone treatment in atrial fibrillation and the risk of incident cancers: A nationwide observational study

BACKGROUND

In observational studies, case reports, and animal studies, amiodarone has been associated with incident cancer.

OBJECTIVE

The purpose of this study was to examine whether a dose-response relationship between amiodarone use and the risk of cancer could be ascertained in a large nationwide study cohort.

METHODS

Using nationwide registers, we included all Danish patients with atrial fibrillation (AF) treated with amiodarone from 1996 to 2014. Exposure was defined both by categories and as a continuous variable of the cumulative defined daily doses (cDDDs) of amiodarone. The associations between amiodarone cDDD and incident cancer, as well as organ-specific types of cancer (skin, liver, lung), were estimated using multivariable Cox regression models and reported as hazard ratios (HR) with 95% confidence intervals (CI) and using cubic restricted spline plots.

RESULTS

We included 18,503 patients with a median follow-up time of 8.1 years (interquartile range [IQR] 4.3-12.4). Median age was 70 years (IQR 63-77). A total of 2974 individuals developed cancer during follow-up. We found no association between increasing amiodarone exposure (cDDD 181-400 and cDDD >400) and the hazard of incident cancer (HR 0.95; 95% CI 0.87-1.04; and HR 1.01; 95% CI 0.92-1.10) with reference to patients with cDDD <181. Similar results were found when investigating specific cancer types (skin, liver, and lung) as well as cDDD as a continuous variable.

CONCLUSION

In a large nationwide cohort of AF patients treated with amiodarone, we found no evidence of a dose-response relationship between cumulative dose of amiodarone and incident cancer risk.

Study on the Role of the Inclusion Complexes with 2-Hydroxypropyl-β-cyclodextrin for Oral Administration of Amiodarone

The aim of this study was to improve the solubility of amiodarone hydrochloride (AMD) and the drug release using its inclusion complexes with 2-hydroxypropyl-β-cyclodextrin (HP-β-CD). The inclusion complexes were prepared by coprecipitation and freeze-drying. The solubility enhancement of AMD/HP-β-CD inclusion complexes by 4–22 times was evaluated by the phase solubility method. The inclusion complexes were studied both in solution and in solid state by spectroscopic methods, dynamic light scattering (DLS) and zeta potential analysis, SEM, and DSC. The formulations of AMD/HP-β-CD inclusion complexes both as powdered form and as matrix tablets showed superior pharmacokinetic performance in improving loading and release properties in respect of those of the insoluble AMD drug. In vitro kinetic study reveals a complex mechanism of release occurring in three steps: the first one being attributed to a burst effect and the other two to different bonding existing in inclusion complexes. An in vivo test on matrix tablets containing Kollidon® and chitosan also reveals a multiple (at least two) peaks release diagram because of both structures of the inclusion complexes and also of different sites of absorption in biological media (digestive tract).

The Effects of Amiodarone on Thyroid Function in Pediatric and Young Adult Patients

CONTEXT

Amiodarone is used in patients with arrhythmias, but thyroid dysfunction [amiodarone-induced thyrotoxicosis (AIT) or amiodarone-induced hypothyroidism (AIH)] is a common adverse effect. As the onset of AIT and AIH has not been studied in children, the timing of dysfunction and long-term monitoring are not known in this population.

OBJECTIVE

To describe the incidence and timing of amiodarone-induced thyroid dysfunction in children and adolescents, with a secondary aim to identify risk factors for amiodarone-induced thyroid dysfunction, and to identify variance in thyroid hormone surveillance and treatment.

DESIGN

Retrospective review of thyroid dysfunction in children and young adults treated with amiodarone between 2007 and 2018.

SETTING

Children's Hospital of Philadelphia.

PATIENTS

Children and young adults treated with amiodarone.

MAIN OUTCOME MEASURES

Prevalence of amiodarone-induced thyroid dysfunction.

RESULTS

Of 484 patients, 190 had thyroid-function testing; 17.3% were found to have subclinical hypothyroidism, and 13.7% testing developed hypothyroidism. Hyperthyroidism occurred in 2.1%. In patients with subclinical hypothyroidism, 63% returned to normal thyroid function without thyroid hormone replacement. Only 26% of patients with hypothyroidism had spontaneous normalization of thyroid function. Twenty-five percent of AIT patients had spontaneous normalization of thyroid function.

CONCLUSIONS

This study looks at a pediatric and young-adult population in an effort to describe the natural history of amiodarone-induced thyroid dysfunction. Based on our data, we recommend that a complete thyroid-function panel be obtained within the first week and then at weekly intervals for the first 5 weeks after initiation. The majority of thyroid dysfunction was noted within the first 35 days of treatment.

Thyrotoxicosis: Diagnosis and Management

Thyrotoxicosis is the clinical manifestation of excess thyroid hormone action at the tissue level due to inappropriately high circulating thyroid hormone concentrations. Hyperthyroidism, a subset of thyrotoxicosis, refers specifically to excess thyroid hormone synthesis and secretion by the thyroid gland. We performed a review of the literature on these topics utilizing published data in PubMed and MEDLINE. In this review, we discuss the more common etiologies of thyrotoxicosis, focusing on the current approach to diagnosis and management, new trends in those directions, and potential upcoming changes in the field.

Rate and rhythm therapy in patients with atrial fibrillation and the risk of pacing and bradyarrhythmia

BACKGROUND

Management of atrial fibrillation (AF) with rate and rhythm therapy can cause bradyarrhythmia.

OBJECTIVES

To assess overall risk, temporal risk, and subgroup at risk of bradyarrhythmia-related events by rate and/or rhythm therapy drugs.

METHODS

Using Danish nationwide registries, patients with AF between 2000 and 2014 were included if prescribed with rate-lowering drugs (RLDs) or antiarrhythmic drugs (AADs). An adjusted time-dependent Poisson regression model estimated the association between RLDs and AADs with a composite endpoint of pacemaker, temporary pacing, and bradyarrhythmia hospitalization. Secondary outcomes were each individual event.

RESULTS

Among 135,017 AF patients, 9196 (6.8%) patients experienced the composite endpoint with a median follow-up of 3.7 (interquartile range [IQR]: 1.6-7.0) years. Median age was 74 (IQR: 65-82) years and 47.6% were women. With rate-lowering monotherapy as the reference, the incidence rate ratios (IRR) (95% confidence interval) for the composite endpoint were 1.36 (1.29-1.43) for rate-lowering dual therapy, 1.62 (1.43-1.84) for antiarrhythmic monotherapy, and 2.49 (2.29-2.71) for AAD combined with RLDs. Similar trend was found for each secondary outcome. Particularly amiodarone increased the risk. This association was strongest within the first 2 weeks of treatment. In those treated with AAD combined with RLDs, high-risk populations were patients ≥70 years (IRR: 3.35 [2.51-4.45] compared to patients <60 years), and women (IRR: 1.35 [1.15-1.57], compared to men).

CONCLUSIONS

In real-world AF patients, rate-lowering dual therapy, antiarrhythmic monotherapy, and AADs combined with RLDs were positively associated with bradyarrhythmia-related events. The risk was highest in those treated with amiodarone, in the initial 2 weeks of treatment, in women, and in the elderly.

Clinical effects of intravenous to oral amiodarone transition strategies in critically ill adult patients

WHAT IS KNOWN AND OBJECTIVE

There is limited guidance on how to transition critically ill patients from intravenous (IV) to oral (PO) amiodarone. The objective of this study was to assess the impact of IV and PO amiodarone overlap on short-term tachyarrhythmia recurrence and adverse hemodynamic outcomes in the intensive care unit.

METHODS

This is a retrospective, single-center analysis of critically ill adults who were treated with IV amiodarone for a supraventricular arrhythmia with rapid ventricular rate (RVR) and transitioned to PO amiodarone while inpatient. Patients were excluded if rate control was not achieved prior to the PO transition. Receipt of concomitant IV and PO therapy for ≤2 hours was considered no overlap (NOV) and >2 hours was considered overlap (OV). Tachyarrhythmia recurrence and adverse hemodynamic events were compared between groups.

RESULTS

A total of 90 patients (45 NOV, 45 OV) were included in the analysis. The median overlap duration was 0.1 (-1.3 to 1.2) hours in the NOV arm and 4 (2.6-6.1) hours in the OV arm. Recurrence of RVR occurred in 9 (20%) patients in each arm (P = 1.0). The median time from IV discontinuation to return of tachyarrhythmia was 10.5 hours. There were no significant differences in amiodarone dosing, electrolyte abnormalities, volume status or concomitant cardiac medications at the time of IV to PO transition. Hypotension occurred in 13% and 20% (P = 0.369) and bradycardia in 9% and 13% (P = 0.502) of patients in the NOV and OV arms, respectively.

WHAT IS NEW AND CONCLUSION

Providing IV and PO overlap of amiodarone for a median of 4 hours did not decrease the rate of early tachyarrhythmia recurrence. Future studies are warranted to evaluate the impact of alternative amiodarone dosing strategies on breakthrough tachyarrhythmia.

Patterns of amiodarone-induced thyroid dysfunction in infants and children

BACKGROUND

Heart Rhythm Society guidelines recommend obtaining thyroid function tests (TFTs) at amiodarone initiation and every 6 months thereafter in adults, with no specific pediatric recommendations. Untreated hypothyroidism in young children negatively affects brain development and somatic growth, yet the optimal screening frequency for pediatric patients remains unclear, and limited data exist on pediatric amiodarone-induced thyroid dysfunction.

OBJECTIVE

The purpose of this study was to describe the patterns of amiodarone-induced thyroid dysfunction in pediatric patients.

METHODS

We established a retrospective cohort of 527 pediatric patients who received amiodarone between 1997 and 2017. We defined amiodarone therapy lasting 3-30 days as "short term" and >30 days as "long term."

RESULTS

The final cohort (n = 150) consisted of 27 neonates (18%), 25 infants (16%), 27 young children (18%), and 71 children (47%). Of the children in whom TFTs were checked, half (50.8%) developed a thyroid-stimulating hormone (TSH) value above the reference for age. Neonates had the highest median peak TSH values in both short- and long-term groups: 23.5 mIU/L (interquartile range 11.4-63.1) and 28.8 mIU/L (interquartile range 11.4-34.4), respectively. Although concurrent use of inotropic support was significantly associated with lower initial TSH values, no variable related to cardiac illness or type of heart disease was associated with peak TSH values.

CONCLUSION

Neonates and infants receiving amiodarone had more thyroid dysfunction with greater degrees of TSH elevation than older children. TSH elevations occurred early, even with short-term exposure. Given the concern for brain development and growth in hypothyroid children, our results suggest the need for more rigorous pediatric-specific thyroid monitoring guidelines.

Importance of in vitro conditions for modeling the in vivo dose in humans by in vitro-in vivo extrapolation (IVIVE)

In vitro studies are increasingly proposed to replace in vivo toxicity testing of substances. We set out to apply physiologically based pharmacokinetic (PBPK) modeling to predict the in vivo dose of amiodarone that leads to the same concentration-time profile in the supernatant and the cell lysate of cultured primary human hepatic cells (PHH). A PBPK human model was constructed based on the structure and tissue distribution of amiodarone in a rat model and using physiological human parameters. The predicted concentration-time profile in plasma was in agreement with human experimental data with the unbound fraction of amiodarone in plasma crucially affecting the goodness-of-fit. Using the validated kinetic model, we subsequently described the in vitro concentration-time data of amiodarone in PHH culture. However, this could be only appropriately modeled under conditions of zero protein binding and the very low clearance of the in vitro system in PHH culture. However, these represent unphysiological conditions and, thus, the main difference between the in vivo and the in vitro systems. Our results reveal that, for meaningful quantitative extrapolation from in vitro to in vivo conditions in PBPK studies, it is essential to avoid non-intended differences between these conditions. Specifically, clearance and protein binding, as demonstrated in our analysis of amiodarone modeling, are important parameters to consider.

Ibutilide for the control of refractory ventricular tachycardia and ventricular fibrillation in patients with myocardial ischemia and hemodynamic instability

INTRODUCTION

Recurrent ventricular tachycardia (VT) and ventricular fibrillation (VF) in patients with myocardial ischemia requiring hemodynamic support can be refractory to available antiarrhythmic agents and even to cardioversion and defibrillation. The purpose of this study was to report the effect of intravenous ibutilide in patients with a VT and/or VF storm in the presence of incomplete revascularization requiring hemodynamic support.

METHODS AND RESULTS

Standard continuous telemetry and frequent 12-lead electrocardiograms were obtained to determine the effect of intravenous Ibutilide in these patients. We studied six consecutive patients (age 60 ± 12 years; five males) with incomplete revascularization and mechanical support (extracorporeal membrane of oxygenation = 2; left ventricular assist device = 4) with VT/VF refractory to lidocaine and amiodarone. Intravenous ibutilide was given as a last resort for management of their ventricular arrhythmias. Intravenous ibutilide (1-2 mg) allowed restoration of sinus rhythm in three patients with persistent VF that were refractory to multiple defibrillation shocks. When the 24-hour period before and after ibutilide administration was compared, this drug markedly reduced the number of required cardioversions/defibrillations in all patients from 20 ± 9 to 0.7 ± 0.8 shocks ( P = 0.036).

CONCLUSIONS

In patients with myocardial ischemia requiring hemodynamic support, intravenous Ibutilide demonstrates a potent antiarrhythmic effect and can facilitate defibrillation in patients with refractory VF.

Intravenous Amiodarone and Sotalol Impair Contractility and Cardiac Output, but Procainamide Does Not: A Langendorff Study

INTRODUCTION

Direct comparison of the effects of antiarrhythmic agents on myocardial performance may be useful in choosing between medications in critically ill patients. Studies directly comparing multiple antiarrhythmic medications are lacking. The use of an experimental heart preparation permits examination of myocardial performance under constant loading conditions.

METHODS

Hearts of Sprague Dawley rats (n = 35, 402-507 g) were explanted and cannulated in working heart model with fixed preload and afterload. Each heart was then exposed to a 3-hour infusion of procainamide (20 µg/kg/min), esmolol (100 or 200 µg/kg/min), amiodarone (10 or 20 mg/kg/d), sotalol (80 mg/m²/d), or placebo infusions (n = 5 per dose). Cardiac output, contractility (dP/dT_max), diastolic performance (dP/dT_min), and heart rate were compared between groups over time by linear mixed modeling.

RESULTS

Compared with placebo, sotalol decreased contractility by an average of 24% ( P < .001) over the infusion period, as did amiodarone (low dose by 13%, P = .029; high dose by 14%, P = .013). Compared with placebo, mean cardiac output was significantly lower in animals treated with sotalol (by 22%, P = .016) and esmolol 200 μg/kg/min (by 23%, P = .012). Over time, amiodarone decreased cardiac output (20 mg/kg/d, β = -89 [-144, -33] μL/min² decrease, P = .002) and also worsened diastolic function, decreasing dP/dT_min by ∼18% and 22% ( P = .032 and P = .011, low and high doses, respectively). Procainamide did not have a significant effect on any measures of systolic or diastolic performance.

CONCLUSIONS

In isolated hearts, amiodarone and sotalol depressed myocardial contractility, cardiac output, and diastolic function. However, procainamide did not negatively affect myocardial performance and represents a favorable agent in settings of therapeutic equivalence.

An Expandable Mechanopharmaceutical Device (2): Drug Induced Granulomas Maximize the Cargo Sequestering Capacity of Macrophages in the Liver

PURPOSE

Drug-induced liver injuries (DILI) comprise a significant proportion of adverse drug reactions leading to hospitalizations and death. One frequent DILI is granulomatous inflammation from exposure to harmful metabolites that activate inflammatory pathways of immune cells of the liver, which may act as a barrier to isolate the irritating stimulus and limit tissue damage.

METHODS

Paralleling the accumulation of CFZ precipitates in the liver, granulomatous inflammation was studied to gain insight into its effect on liver structure and function. A structural analog that does not precipitate within macrophages was also studied using micro-analytical approaches. Depleting macrophages was used to inhibit granuloma formation and assess its effect on drug bioaccumulation and toxicity.

RESULTS

Granuloma-associated macrophages showed a distinct phenotype, differentiating them from non-granuloma macrophages. Granulomas were induced by insoluble CFZ cargo, but not by the more soluble analog, pointing to precipitation being a factor driving granulomatous inflammation. Granuloma-associated macrophages showed increased activation of lysosomal master-regulator transcription factor EB (TFEB). Inhibiting granuloma formation increased hepatic necrosis and systemic toxicity in CFZ-treated animals.

CONCLUSIONS

Granuloma-associated macrophages are a specialized cell population equipped to actively sequester and stabilize cytotoxic chemotherapeutic agents. Thus, drug-induced granulomas may function as drug sequestering "organoids" -an induced, specialized sub-compartment- to limit tissue damage.

A Rare Case of Spontaneous Cardiac Tamponade Induced by Concomitant Use of Rivaroxaban and Amiodarone

Rivaroxaban is a direct oral anticoagulant (DOAC) approved as an important alternative to warfarin in patients with nonvalvular atrial fibrillation. We report the case of an 87-year-old man with past medical history of nonvalvular atrial fibrillation on rivaroxaban and recently started amiodarone for pulseless ventricular tachycardia who presented to our hospital with intermittent chest pain and was diagnosed with spontaneous hemopericardium causing cardiac tamponade. The culprit drugs were discontinued, and the patient was treated with emergent pericardiocentesis. Both rivaroxaban and amiodarone are substrates for the CYP3A4 hepatic pathway, and concomitant use can result in increased plasma rivaroxaban levels causing an increased propensity to bleeding. While most physicians are cognizant of the need for renal dosing of rivaroxaban, this article aims to increase awareness of its interactions with drugs that are also metabolized through the same hepatic CYP450 pathway.

Cardiovascular pharmacology of K2P17.1 (TASK-4, TALK-2) two-pore-domain K+ channels

K_2P17.1 (TASK-4, TALK-2) potassium channels are expressed in the heart and represent potential targets for pharmacological management of atrial and ventricular arrhythmias. Reduced K_2P17.1 expression was found in atria and ventricles of heart failure (HF) patients. Modulation of K_2P17.1 currents by antiarrhythmic compounds has not been comprehensively studied to date. The objective of this study was to investigate acute effects of clinically relevant antiarrhythmic drugs on human K_2P17.1 channels to provide a more complete picture of K_2P17.1 electropharmacology. Whole-cell patch clamp and two-electrode voltage clamp electrophysiology was employed to study human K_2P17.1 channel pharmacology. K_2P17.1 channels expressed in Xenopus laevis oocytes were screened for sensitivity to antiarrhythmic drugs, revealing significant activation by propafenone (+ 296%; 100 μM), quinidine (+ 58%; 100 μM), mexiletine (+ 21%; 100 μM), propranolol (+ 139%; 100 μM), and metoprolol (+ 17%; 100 μM) within 60 min. In addition, the currents were inhibited by amiodarone (- 13%; 100 μM), sotalol (- 10%; 100 μM), verapamil (- 21%; 100 μM), and ranolazine (- 8%; 100 μM). K_2P17.1 channels were not significantly affected by ajmaline and carvedilol. Concentration-dependent K_2P17.1 activation by propafenone was characterized in more detail. The onset of activation was fast, and current-voltage relationships were not modulated by propafenone. K_2P17.1 activation was confirmed in mammalian Chinese hamster ovary cells, revealing 7.8-fold current increase by 100 μM propafenone. Human K_2P17.1 channels were sensitive to multiple antiarrhythmic drugs. Differential pharmacological regulation of repolarizing K_2P17.1 background K⁺ channels may be employed for personalized antiarrhythmic therapy.

Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes Reveal Bradycardiac Effects Caused by Co-Administration of Sofosbuvir and Amiodarone

Co-administration of sofosbuvir, an anti-hepatitis C virus medication, and antiarrhythmic amiodarone causes symptomatic severe bradycardia in patients and animal models. However, in a few in vitro studies, the combination of sofosbuvir and amiodarone resulted in tachycardiac effects in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). This discrepancy may be attributable to the use of immature hiPSC-CMs in the in vitro studies. To address this, we evaluated the ability of our in-house hiPSC-CMs to assess the interactions between sofosbuvir and amiodarone in vitro. We performed whole-cell patch recordings on hiPSC-CMs to examine the cardiac effect of sofosbuvir and amiodarone, alone or in combination. We found that sofosbuvir and amiodarone caused bradycardiac effects (the beating rate decreased to 75% of the vehicle control, P < 0.001) on our hiPSC-CMs when applied in combination, but they had no significant effect when applied alone. Furthermore, the bradycardiac effect was membrane potential dependent: it increased with depolarization. This raised the possibility that the bradycardiac effects in vivo may originate in nodal cells, which have a more depolarized resting membrane potential compared with ventricular cells. The bradycardiac effects of sofosbuvir plus amiodarone in vitro are consistent with the clinical phenotype and suggest that our hiPSC-CMs may serve as a useful tool in assessing cardiac safety during drug discovery and development process.

Identification and characterization of amiodarone metabolites in rats using UPLC-ESI-QTOFMS-based untargeted metabolomics approach

Amiodarone is a class III anti-arrhythmic benzofuran derivative extensively utilized in treatment of life-threatening ventricular and supraventricular arrhythmias. However, amiodarone also produces adverse side effects including liver injury due to its metabolites rather than parent drug. The purpose of the present study was to identify metabolites of amiodarone in the plasma and urine of rats administered the drug by using an untargeted metabolomics approach. Drug metabolites were profiled by ultra-performance liquid chromatography-linked electrospray ionization quadrupole time-of-flight mass spectrometry (UPLC-ESI-QTOFMS) and results subjected to multivariate data analysis. A total of 49 amiodarone metabolites were identified and their structures were characterized by tandem mass spectrometry. Amiodarone metabolites are presumed to be generated via five major types of metabolic reactions including N-desethylation, hydroxylation, carboxylation (oxo/hydroxylation), de-iodination, and glucuronidation. Data demonstrated that an untargeted metabolomics approach appeared to be a reliable tool for identifying unknown metabolites in a complex biological matrix.