Digoxin level and clinical manifestations as determinants in the diagnosis of digoxin toxicity

Predictive Factors for Recurrence of Serious Arrhythmias in Patients with Acute Digoxin Poisoning

Although digoxin poisoning has declined in the past decades, it still has deleterious outcomes. The hallmark of serious life-threatening arrhythmias remains challenging due to its non-specific initial presentation. Therefore, this study aimed to evaluate the initial predictive factors for recurrent serious arrhythmias and the need for temporary pacing in acute digoxin-poisoned patients. This retrospective cohort study included all patients with acute digoxin poisoning admitted to Tanta University Poison Control Center from 2017 to 2020. Demographic and toxicological data, poisoning severity score (PSS), laboratory investigations, and serial ECG monitoring data were documented. Patients were divided according to their age into a childhood group and adolescence & adulthood group. Each age group was divided into two subgroups according to the presence of recurrent serious arrhythmias. Patient outcomes, including intensive care unit admission, temporary pacing, and in-hospital mortality were recorded. A percentage of 37.34% (n = 31) of the included patients had recurrent serious arrhythmias in both groups. Recurrent serious arrhythmias groups had significantly low heart rate, prolonged PR interval, high PSS, Mobitz II dysrhythmias, elevated serum digoxin, serum potassium and serum creatinine, and increased adverse outcomes compared to other groups. Logistic regression analysis showed that only serum digoxin and potassium levels were significant independent predictors of recurrent serious arrhythmias and temporary pacing. Serum digoxin level had an excellent discriminatory power with the best sensitivity and specificity, followed by serum potassium level in both groups. Thus, monitoring serum digoxin and potassium levels is essential in all patients with acute digoxin poisoning, especially with limited Fab availability.

Maternal effects induced by oral digoxin during treatment of fetal tachyarrhythmia: Case series and literature review

OBJECTIVES

The aim of this study is to evaluate the prevalence of maternal complications derived from digoxin treatment and its relationship with digoxinemia, as well as its occurrence in relation to the different treatment doses and therapeutic schemes used.

STUDY DESIGN

This is a retrospective observational study of women who received digoxin for the treatment of fetal tachyarrhythmia over a 10-year period at the University Hospital Virgen del Rocío (Seville). Data corresponding to the digoxin dose, its duration, serum digoxin levels and electrocardiographic parameters during follow-up were collected. Maternal side effects were reported, and its relationship to the treatment dose as well as digoxinemia. The study is accompanied by a narrative review of related literature.

RESULTS

There were 10 cases eligible. During treatment, as least one symptom or sign was present in 30 % of cases, being in all cases digestive symptoms. In all those cases, the digoxin level was higher than established as therapeutic threshold (2 ng/mL), and all reversed within a maximum of 48 h after the dose decrease. Digoxinemia overdosing (> 2 ng/mL) was observed in 6 women (60 %), one of which reached the toxicity range (> 3 ng/mL). In all cases, normal range was achieved decreasing the dose of digoxin 0.25 mg every 24 h. No patient developed side effects with digoxinemia below 2 ng/mL. No electrocardiographic abnormalities appeared during treatment.

CONCLUSION

Digoxin is a safe treatment for management of fetal tachyarrhythmias. Side effects appear frequently when serum digoxin level is over 2 ng/mL, but they are usually mild and self-limited. However, it remains advisable to monitor electrocardiographic changes and digoxinemia through the whole therapy to prevent serious complications related to digoxin toxicity.

Outcomes and Costs of Poisoned Patients Admitted to an Adult Emergency Department of a Spanish Tertiary Hospital: Evaluation through a Toxicovigilance Program

Abstract

Toxicovigilance is the active process of identifying and evaluating the toxic risks existing in a community, and evaluating the measures taken to reduce or eliminate them.

Objective

Through a validated toxicovigilance program (SAT-HULP) we examined the characteristics of acute poisoning cases (APC) attended in the Emergency Department (ED) of La Paz Hospital (Madrid, Spain) and assessed their economic impact on the health system.

Material and Methods

The active poisoning surveillance system performs a daily search for cases in the hospital´s computerized case records. Found cases are entered into a database for recording of type of poisoning episode, reasons for exposure, causative agent, signs and symptoms and treatment. We carried out a cross-sectional epidemiological study with analytical projection, based on an impact study on cost per survivor. The data for the costs attributable to cases of APC observed at HULP (outpatients and inpatients) was obtained from the based on the information provided by the diagnosis-related groups (DRG) through the corresponding hospital discharge reports (available through SAT-HULP).

Results

During the first 30 month of SAT-HULP operation we found a total of 3,195 APC, a cumulative incidence rate of 1.75% of patients attended in the ED. The mean (SD) patient age was 40.9 (17.8) years and 51.2% were men. Drug abuse accounted for 47.5% of the cases. Suicide attempt was the second most frequent category (38.1%) and other causes accounted for 14.5% of APC. The total cost of hospital care for our hospital rose to €1,825,263.24 (approximately €730,105.30/year) resulting in a permanent occupation of 4 beds/year.

Conclusions

SAT-HULP constitutes a validated toxicovigilance tool, which continuously integrates available data in real-time and helps health services manage APC data flexibly, including the consumption of resources from the health system.

Pharmacological treatment of cardiac glycoside poisoning

Cardiac glycosides are an important cause of poisoning, reflecting their widespread clinical usage and presence in natural sources. Poisoning can manifest as varying degrees of toxicity. Predominant clinical features include gastrointestinal signs, bradycardia and heart block. Death occurs from ventricular fibrillation or tachycardia. A wide range of treatments have been used, the more common including activated charcoal, atropine, β-adrenoceptor agonists, temporary pacing, anti-digoxin Fab and magnesium, and more novel agents include fructose-1,6-diphosphate (clinical trial in progress) and anticalin. However, even in the case of those treatments that have been in use for decades, there is debate regarding their efficacy, the indications and dosage that optimizes outcomes. This contributes to variability in use across the world. Another factor influencing usage is access. Barriers to access include the requirement for transfer to a specialized centre (for example, to receive temporary pacing) or financial resources (for example, anti-digoxin Fab in resource poor countries). Recent data suggest that existing methods for calculating the dose of anti-digoxin Fab in digoxin poisoning overstate the dose required, and that its efficacy may be minimal in patients with chronic digoxin poisoning. Cheaper and effective medicines are required, in particular for the treatment of yellow oleander poisoning which is problematic in resource poor countries.

Management of digoxin toxicity

Digoxin toxicity can emerge during long-term therapy as well as after an overdose. It can occur even when the serum digoxin concentration is within the therapeutic range. Toxicity causes anorexia, nausea, vomiting and neurological symptoms. It can also trigger fatal arrhythmias. There is a range of indications for using digoxin-specific antibody fragments. The amount ingested and serum digoxin concentration help to determine the dose required, but are not essential. Digoxin-specific antibody fragments are safe and effective in severe toxicity. Monitoring should continue after treatment because of the small risk of rebound toxicity. Restarting therapy should take into account the indication for digoxin and any reasons why the concentration became toxic.

A population pharmacokinetic analysis of the influence of nutritional status of digoxin in hospitalized Korean patients

BACKGROUND

Safe and effective use of digoxin in hospitalized populations requires information about the drug's pharmacokinetics and the influence of various factors on drug disposition. However, no attempts have been made to link an individual's digoxin requirements with nutritional status.

OBJECTIVES

The main goal of this study was to estimate the population pharmacokinetics of digoxin and to identify the nutritional status that explains pharmacokinetic variability in hospitalized Korean patients.

METHODS

Routine therapeutic drug-monitoring data from 106 patients who received oral digoxin at Seoul National University Bundang Hospital were retrospectively collected. The pharmacokinetics of digoxin were analyzed with a 1-compartment, open-label pharmacokinetic model by using a nonlinear mixed-effects modeling tool (NONMEM) and a multiple trough screening approach.

RESULTS

The effect of demographic characteristics and biochemical and nutritional indices were explored. Estimates generated by using NONMEM indicated that the CL/F of digoxin was influenced by renal function, serum potassium, age, and percentage of ideal body weight (PIBW). These influences could be modeled by following the equation CL/F (L/h) = 1.36 × (creatinine clearance/50)(1.580) × K(0.835) × 0.055 × (age/65) × (PIBW/100)(0.403). The interindividual %CV for CL/F was 34.3%, and the residual variability (SD) between observed and predicted concentrations was 0.225 μg/L. The median estimates from a bootstrap procedure were comparable and within 5% of the estimates from NONMEM. Correlation analysis with the validation group showed a linear correlation between observed and predicted values.

CONCLUSIONS

The use of this model in routine therapeutic drug monitoring requires that certain conditions be met which are consistent with the conditions of the subpopulations in the present study. Therefore, further studies are needed to clarify the effects of nutritional status on digoxin pharmacokinetics. The present study established important sources of variability in digoxin pharmacokinetics and highlighted the relationship between pharmacokinetic parameters and nutritional status in hospitalized Korean patients.

Possible digoxin toxicity associated with concomitant ciprofloxacin therapy

CASE (DESCRIPTION)

A 27 year old female with a complex history of congenital heart disease, cardiac surgery, heart failure, and arrhythmias was admitted for a Pseudomonas aeruginosa sternal wound infection and treated with intravenous antibiotics. After discharge and completion of an outpatient course of intravenous antibiotics, suppressive antibiotic therapy with ciprofloxacin was initiated. She presented to clinic with nausea and anorexia within a few days of addition of ciprofloxacin to her current regimen of medications, which included digoxin. The digoxin was discontinued, with all other medications remaining the same, and the symptoms resolved in 48 h. The dose of digoxin was restarted at 50 % of the previous dose with no further complications. The proposed cause of the nausea and anorexia was digoxin toxicity secondary to a drug-drug interaction with ciprofloxacin.

CONCLUSION

Patients receiving ciprofloxacin and digoxin should be monitored closely for the risk of digoxin toxicity.

Interaction of digitalis-like compounds with p-glycoprotein

Digitalis-like compounds (DLCs), or cardiac glycosides, are produced and sequestered by certain plants and animals as a protective mechanism against herbivores or predators. Currently, the DLCs digoxin and digitoxin are used in the treatment of cardiac congestion and some types of cardiac arrhythmia, despite a very narrow therapeutic index. P-glycoprotein (P-gp; ABCB1) is the only known ATP-dependent efflux transporter that handles digoxin as a substrate. Ten alanine mutants of human P-gp drug-binding amino acids-Leu(65), Ile(306), Phe(336), Ile(340), Phe(343), Phe(728), Phe(942), Thr(945), Leu(975), and Val(982)-were generated and expressed in HEK293 cells with a mammalian baculovirus system. The uptake of [(3)H]-N-methyl-quinidine (NMQ), the P-gp substrate in vesicular transport assays, was determined. The mutations I306A, F343A, F728A, T945A, and L975A abolished NMQ transport activity of P-gp. For the other mutants, the apparent affinities for six DLCs (cymarin, digitoxin, digoxin, peruvoside, proscillaridin A, and strophanthidol) were determined. The affinities of digoxin, proscillaridin A, peruvoside, and cymarin for mutants F336A and I340A were decreased two- to fourfold compared with wild type, whereas that of digitoxin and strophanthidol did not change. In addition, the presence of a hydroxyl group at position 12β seems to reduce the apparent affinity when the side chain of Phe(336) and Phe(942) is absent. Our results showed that a δ-lactone ring and a sugar moiety at 3β of the steroid body are favorable for DLC binding to P-gp. Moreover, DLC inhibition is increased by hydroxyl groups at positions 5β and 19, whereas inhibition is decreased by those at positions 1β, 11α, 12β, and 16β. The understanding of the P-gp-DLC interaction improves our insight into DLCs toxicity and might enhance the replacement of digoxin with other DLCs that have less adverse drug effects.

Indinavir Trough Concentration as a Determinant of Early Nephrolithiasis in HIV-1-Infected Adults

Indinavir plasma levels are associated with antiretroviral efficacy; however, little data are available regarding toxicity. We assessed the relationship between indinavir pharmacokinetic (PK) characteristics and severe nephrolithiasis as well as other severe or serious adverse reactions. Patients included in the ANRS CO8 APROCO-COPILOTE cohort and receiving 800 mg indinavir three times daily as a first-line protease inhibitor were eligible for this study. To be included in the analysis, their plasma sample at month 1 (M1) had to be available (n = 282) to estimate using population PK modeling, indinavir PK characteristics, ie, maximum (Cmax) and trough plasma (Cres) concentrations, area under the curve (AUC), and observed/predicted concentration ratio (CR). A Cox model was used to estimate the independent effect of Cmax, Cres, AUC, and CR on the hazard of severe nephrolithiasis and serious adverse reactions. At M1, median Cmax was 6205 ng/mL, Cres 631 ng/mL, AUC 24,242 ng . h/mL, and CR 0.6. After a median follow up of 12 months, 11% of patients (30 of 282) had experienced at least one serious adverse reaction among which 12 were nephrolithiasis. In the multivariate analyses, early high indinavir Cres (ie, >/=1000 ng/mL at M1) was associated with a higher rate of severe nephrolithiasis (hazard ratio = 6.7; 95% confidence interval = 1.8-25.2; P < 0.01) and was also associated with a higher rate of all serious adverse reactions but only when nephrolithiasis were included among those cases. Prospective and early indinavir Cres determination should be recommended in the patient's care management and dosage adjustments.

Suspected DLIS Interference in the Dimension DGNA Digoxin Assay Method and the Clinical Application of the Revised Digoxin Target Range

The authors present a case of an elderly female patient with heart failure and renal dysfunction treated with digoxin, where 2 commercial immunoassay methods (DRI, Microgenics, and DGNA, Dade Behring) showed a clinically very significant discrepancy on the same plasma sample, viz. 0.5 and 2.3 nmol/L, respectively. The sample was also referred to a third external laboratory that returned a result of 0.9 nmol/L using mFPIA (AxSYM, Abbott). Subsequent ultrafiltration (30,000 Dalton) on the sample essentially eliminated the difference, suggesting an interference from a large molecular weight compound(s), potentially the well-described digoxin-like immunoreactive substance(s) (DLIS). Although further study is required to verify that the DLIS implicated was indeed the interfering species, it does again highlight the importance of careful method selection in the clinical therapeutic drug monitoring laboratory to ensure that such well-established potential problems do not result in inappropriate dosage reduction with consequent lack of adequate drug exposure and serious clinical sequelae.

Mechanisms, manifestations, and management of digoxin toxicity in the modern era

Because of the common use of digoxin and because of its narrow therapeutic index, digoxin toxicity has been prevalent historically and, therefore, most clinicians are well aware of the classical dose/concentration-related signs and symptoms of toxicity. Yet, in the modern era the incidence of digoxin toxicity has been declining for a variety of reasons, including a new (lower) therapeutic range, the development of more effective drug therapies for heart failure, and more accurate dosing methods. In addition, digoxin toxicity, once commonly fatal, can now be quickly and effectively treated by the emergency administration of antidigoxin Fab fragments. Indeed, it may be possible to expand the use of Fab fragments to select patients with non-life-threatening digoxin toxicity, in order to save costs and improve patient comfort. Most cases of digoxin toxicity are caused by inappropriately high dosages, which are usually prescribed in the setting of renal dysfunction, while other cases can be attributed to system errors such as multiple prescriptions, poor patient counseling, or errors in transcribing. With modern computerized prescribing systems, such as direct physician order entry and prompts that alert the clinician to the potential for error, it is possible to decrease the incidence of digoxin toxicity even further. A realistic goal is to nearly eradicate once commonplace digoxin toxicity or at least make its occurrence a rare event.