Incidence of hospitalization for digitalis toxicity among elderly Americans

Hawthorn (Crataegus spp.) in the treatment of cardiovascular disease

The medicinal properties of hawthorn (Crataegus spp., a genus comprising approximately 300 species) have been utilized by many cultures for a variety of therapeutic purposes for many centuries. In the Western world cardiovascular disease (CVD) has become one of the single most significant causes of premature death. Echoing this situation, more recent research into the therapeutic benefits of hawthorn preparations has focused primarily upon its cardiovascular effects. This review covers research into the various mechanisms of action proposed for Crataegus preparations, clinical trials involving Crataegus preparations, and the herb's safety profile.Clinical trials reviewed have been inconsistent in terms of criteria used (sample size, preparation, dosage, etc) but have been largely consistent with regard to positive outcomes. An investigation into data available to date regarding hawthorn preparations and herb/drug interactions reveals that theoretical adverse interactions have not been experienced in practice. Further, adverse reactions relating to the use of hawthorn preparations are infrequent and mild, even at higher dosage ranges. A recent retrospective study by Zick et al. has suggested a negative outcome for the long-term use of hawthorn in the prognosis of heart failure. These findings are examined in this paper.Although further research is needed in certain areas, current research to date suggests that hawthorn may potentially represent a safe, effective, nontoxic agent in the treatment of CVD and ischemic heart disease (IHD).

Hawthorn extract for treating chronic heart failure

BACKGROUND

Hawthorn extract is advocated as an oral treatment option for chronic heart failure. Also, the German Commission E approved the use of extracts of hawthorn leaf with flower in patients suffering from heart failure graded stage II according to the New York Heart Association.

OBJECTIVES

To assess the benefits and harms as reported in double-blind randomised clinical trials of hawthorn extract compared with placebo for treating patients with chronic heart failure.

SEARCH STRATEGY

We searched CENTRAL on The Cochrane Library (issue 2, 2006), MEDLINE (1951 to June 2006), EMBASE (1974 to June 2006), CINAHL (1982 to June 2006) and AMED (1985 to June 2006). Experts and manufacturers were contacted. Language restrictions were not imposed.

SELECTION CRITERIA

To be included, studies were required to state that they were randomised, double-blind, and placebo controlled, and used hawthorn leaf and flower extract monopreparations.

DATA COLLECTION AND ANALYSIS

Two reviewers independently performed the selection of studies, data extraction, and assessment of methodological quality. Data were entered into RevMan 4.2 software. Results from continuous data were reported as weighted mean difference (WMD) with 95% confidence interval (CI). Where data were suitable for combining, pooled results were calculated.

MAIN RESULTS

Fourteen trials met all inclusion criteria and were included in this review. In most of the studies, hawthorn was used as an adjunct to conventional treatment. Ten trials including 855 patients with chronic heart failure (New York Heart Association classes I to III) provided data that were suitable for meta-analysis. For the physiologic outcome of maximal workload, treatment with hawthorn extract was more beneficial than placebo (WMD (Watt) 5.35, 95% CI 0.71 to 10.00, P < 0.02, n = 380). Exercise tolerance were significantly increased by hawthorn extract (WMD (Watt x min) 122.76, 95% CI 32.74 to 212.78, n = 98). The pressure-heart rate product, an index of cardiac oxygen consumption, also showed a beneficial decrease with hawthorn treatment (WMD (mmHg/min) -19.22, 95% CI -30.46 to -7.98, n = 264). Symptoms such as shortness of breath and fatigue improved significantly with hawthorn treatment as compared with placebo (WMD -5.47, 95% CI -8.68 to -2.26, n = 239). No data on relevant mortality and morbidity such as cardiac events were reported, apart from one trial, which reported deaths (three in active, one in control) without providing further details. Reported adverse events were infrequent, mild, and transient; they included nausea, dizziness, and cardiac and gastrointestinal complaints.

AUTHORS' CONCLUSIONS

These results suggest that there is a significant benefit in symptom control and physiologic outcomes from hawthorn extract as an adjunctive treatment for chronic heart failure.

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.

Cardiotoxicity of digitalis glycosides: roles of autonomic pathways, autacoids and ion channels

1 Cardiac glycosides have been used for centuries as therapeutic agents for the treatment of heart diseases. In patients with heart failure, digoxin and the other glycosides exert their positive inotropic effect by inhibiting Na(+)-K(+)-ATPase, thereby increasing intracellular sodium, which, in turn, inhibits the Na(+)/Ca(2+) exchanger and increases intracellular calcium levels. As the therapeutic index of digitalis is narrow, arrhythmias are common problems in clinical practice. The mechanisms and mediators of these arrhythmias, however, are not completely understood. 2 The involvement of the sympathetic and parasympathetic nervous system in digitalis cardiac toxicity is reviewed. 3 Receptors, channels, exchange systems or other cellular components involved in digitalis-induced cardiotoxicity are also reviewed. 4 Possible mediators of digitalis-induced cardiac toxicity are discussed. 5 Management of digitalis toxicity in patients is summarized. 6 The determination of the possible mediators of digitalis-induced cardiac toxicity will enhance our knowledge and lead to the development of new therapeutic strategies to treat these lethal arrhythmias.

Hawthorn extract for treating chronic heart failure: meta-analysis of randomized trials

The aim of this meta-analysis was to assess the evidence from rigorous clinical trials of the use of hawthorn extract to treat patients with chronic heart failure. We searched the literature using MEDLINE, EMBASE, the Cochrane Library, CINAHL, CISCOM, and AMED. Experts on and manufacturers of commercial preparations containing hawthorn extract were asked to contribute published and unpublished studies. There were no restrictions about the language of publication. Two reviewers independently performed the screening of studies, selection, validation, data extraction, and the assessment of methodological quality. To be included, studies were required to state that they were randomized, double-blind, and placebo controlled, and used hawthorn extract monopreparations. Thirteen trials met all inclusion criteria. In most of the studies, hawthorn was used as an adjunct to conventional treatment. Eight trials including 632 patients with chronic heart failure (New York Heart Association classes I to III) provided data that were suitable for meta-analysis. For the physiologic outcome of maximal workload, treatment with hawthorn extract was more beneficial than placebo (weighted mean difference, 7 Watt; 95% confidence interval [CI]: 3 to 11 Watt; P < 0.01; n = 310 patients). The pressure-heart rate product also showed a beneficial decrease (weighted mean difference, -20; 95% CI: -32 to -8; n = 264 patients) with hawthorn treatment. Symptoms such as dyspnea and fatigue improved significantly with hawthorn treatment as compared with placebo. Reported adverse events were infrequent, mild, and transient; they included nausea, dizziness, and cardiac and gastrointestinal complaints. In conclusion, these results suggest that there is a significant benefit from hawthorn extract as an adjunctive treatment for chronic heart failure.

Use of Digoxin Monitoring in a Hospital Setting as an Essential Tool in Optimizing Therapy

Objective

To determine what triggers the use of digoxin therapeutic drug monitoring (TDM) that adheres to established indications and the change in digoxin dosage after the result of monitoring is obtained.

Methods

This prospective study included 86 patients admitted to 6 medicine wards and 2 intensive cardiac care unit wards in a tertiary-care center. Data on patients' demographics, drug therapy, serum chemistry values, indications for digoxin therapy, indications for ordering the drug assay, timing of the blood sample relative to administration of the last dose, and physicians' decisions after attaining serum digoxin concentrations were collected.

Results

Eighty-six digoxin assays were evaluated. Indications for the use of a digoxin assay were mostly routine without a clear indication (66%); in only 22% of the assays were orders considered clinically justified. Eleven patients had concentrations >2 ng/mL, but only 8 patients had digoxin intoxication. In only 31% of patients did the medical staff respond to the results. In only 21% of patients with subtherapeutic drug concentrations was there a change in digoxin dose.

Conclusions

Although there are clear indications for the use of digoxin TDM, physicians seem to routinely order these blood tests. The clinicians did not adequately use the digoxin concentration data to optimize therapy. The assistance of a clinical pharmacist or pharmacologist is warranted for use of the assays, to optimize digoxin therapy.

Electrocardiographic manifestations: digitalis toxicity

Toxicity from the digitalis family of cardiac glycoside medications remains common. Successful treatment depends on early recognition; however, the diagnosis of potentially life-threatening toxicity remains difficult because the clinical presentation is often nonspecific and subtle. The hallmark of cardiac toxicity is increased automaticity coupled with concomitant conduction delay. Though no single dysrhythmia is always present, certain aberrations such as frequent premature ventricular beats, bradydysrhythmias, paroxysmal atrial tachycardia with block, junctional tachycardia, and bidirectional ventricular tachycardia are common. Treatment depends on the clinical condition rather than serum drug level. Management varies from temporary withdrawal of the medication to administration of digoxin-specific Fab fragments for life-threatening cardiovascular compromise.

Drug therapy of heart failure caused by systolic dysfunction in the elderly

The presence of multiple medical illnesses often distinguishes elderly patients with heart failure and can make pharmacologic management of symptomatic heart failure challenging in this population. Physiologic changes that occur with normal aging may complicate clinical assessment. Limited data from large clinical trials of heart failure therapy are applicable to aged patients. Available data suggest that elderly patients should be treated with the same regimen as younger patients but that more careful attention should be paid to dosing, especially when initiating a new drug. History and physical examination techniques can be used to uncover evidence of congestion and inadequate perfusion and are critical adjuncts when making therapeutic decisions. The objectives of therapy for elderly patients with heart failure must be individualized within the larger context of patients' goals and stage of life.

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

The aim of this study was to determine the relative importance of different risk factors in the diagnosis of digitalis toxicity. The authors recruited inpatients for whom serum digoxin level was requested and prospectively followed them for a week to ascertain if they showed digitalis toxicity. The predictive value of different factors for the assessment of digoxin toxicity was analyzed by multiple logistic regression. Forty-one toxic and 58 nontoxic patients were included. In the univariant analysis, intoxicated patients were older, most were women, and they had worse renal function and higher digoxin level; but there were no differences in serum electrolytes or other risk factors. In the multivariant analysis, digoxin level was the only independent factor related to digitalis toxicity. A different risk of toxicity for each clinical manifestation was found for a certain digoxin level. Patients with signs of automaticity in the electrocardiogram had a higher likelihood of being intoxicated than patients with gastrointestinal symptoms, atrioventricular block, or bradycardia. Therefore, in the population evaluated in this study, digoxin level is the key independent factor in digoxin intoxication, although the probability of being intoxicated is also a function of the type of clinical manifestations. A graphic approximation of this probability based on these two factors is presented.

Isolation and Characterization of Human Monoclonal Antibodies to Digoxin

Fab preparations of sheep polyclonal anti-digoxin Abs have proven useful for reversal of the toxic effects of digoxin overdoses in patients. Unfortunately, the use of foreign species proteins in humans is limited because of the potential for immunological responses that include hypersensitivity reactions and acute anaphylaxis. Immunization of recently developed transgenic mice, whose endogenous μ heavy and κ light chain Ig genes are inactivated and which carry human Ig gene segments, with a digoxin-protein conjugate has enabled us to generate and isolate eight hybridoma cell lines secreting human sequence anti-digoxin mAbs. Six of the mAbs have been partially characterized and shown to have high specificity and low nanomolar affinities for digoxin. In addition, detailed competition binding studies performed with three of these mAbs have shown them to have distinct differences in their digoxin binding, and that all three structural moieties of the drug, the primary digitoxose sugar, steroid, and five-member unsaturated lactone ring, contribute to Ab recognition.

Frequency and cost of serious adverse drug reactions in a department of general medicine

AIMS

To assess the frequency and cost of drug reactions causing or prolonging hospitalization.

METHODS

All patients admitted to an internal medicine ward over 6 months were evaluated to identify serious adverse reactions. The number of drug classes on admission or at the time of the adverse drug reaction (ADR) was counted. Excess ADR-related hospital stay was computed using a) raw excess duration of hospital stay, b) correction of duration of hospital stay by age, sex, and number of drug classes, and c) estimation by investigator of excess hospital stay.

RESULTS

Three hundred and twenty-nine patients were evaluated: 212 male, 117 female, mean age 57.2 (males: 52.2, females: 66.2 (P < 0.05)), range 17-95 years. They stayed a total of 3720 hospital days (mean stay 11.3 days). 298 had no ADR (mean age 55.8, taking a mean of 2.7 drug classes, 10.7 days hospital stay); 31 had ADRs: in 10, the ADR caused admission in patients with a mean age of 84 (P < 0.01 vs the two other groups), taking 6.3 drug classes, who stayed a mean of 15.1 days; 21 occurred in hospital in patients with a mean age of 63.6, taking 4.2 drug classes (P < 0.01), who stayed a mean of 19.2 days (P < 0.01 vs patients without ADRs). In four the ADR was fatal (13% of ADRs, 40% of deaths). Raw ADR-related excess hospital stay was 318 days (8.6% of all hospital days), after multivariate correction 282 days (7.6% of all hospital days), and with investigator estimation 197 days (5.3% of all hospital days). Point prevalence of ADRs at admission was 3%, incidence rate in hospital was 5.6/1000 patient-days.

CONCLUSIONS

3% of the admissions were related to ADRs. In addition, 6.6% of hospitalized patients had significant ADRs. Between 5 and 9% of hospital costs were related to ADRs. In 24 of the 31 patients with ADRs (77%), these were related to the pharmacological properties of the involved drugs, and may possibly have been avoidable.

Does digoxin provide additional hemodynamic and autonomic benefit at higher doses in patients with mild to moderate heart failure and normal sinus rhythm?

OBJECTIVES

This study sought to examine the hemodynamic and autonomic dose response to digoxin.

BACKGROUND

Previous studies have demonstrated an increase in contractility and heart rate variability with digitalis preparations. However, little is known about the dose-response to digoxin, which has a narrow therapeutic window.

METHODS

Nineteen patients with moderate heart failure and a left ventricular ejection fraction < 0.45 were studied hemodynamically using echocardiography and blood pressure at baseline and after 2 weeks of low dose (0.125 mg daily) and 2 weeks of moderate dose digoxin (0.25 mg daily). Loading conditions were altered with nitroprusside at each study. Autonomic function was studied by assessing heart rate variability on 24-h Holter monitoring and plasma norepinephrine levels during supine rest.

RESULTS

Low dose digoxin provided a significant increase in ventricular performance, but no further increase was seen with the moderate dose. Low dose digoxin reduced heart rate and increased heart rate variability. Moderate dose digoxin produced no additional increase in heart rate variability or reduction in sympathetic activity, as manifested by heart rate, plasma norepinephrine or low frequency/high frequency power ratio. In addition, we did not find that either low or moderate dose digoxin increased parasympathetic activity.

CONCLUSIONS

We conclude that moderate dose digoxin provides no additional hemodynamic or autonomic benefit for patients with mild to moderate heart failure over low dose digoxin. Because higher doses of digoxin may predispose to arrhythmogenesis, lower dose digoxin should be considered in patients with mild to moderate heart failure.

Changing physician behavior in ordering digoxin assays

OBJECTIVE

To assess the ability to modify physicians' use of serum digoxin assays in a sustained fashion through (1) an educational intervention by a clinical pharmacist, and (2) changes in the computerized medical information system.

DESIGN

A before/after methodology was used to compare test use by hospital staff physicians in two phases. Phase 1 was an educational intervention conducted by a clinical pharmacist with an 8-month follow-up. Phase 2 was a medical information system intervention with a 12-month follow-up.

PATIENTS

Adult inpatients from July 1990 through December 1993 who received either digoxin therapy or at least one serum digoxin assay.

MAIN OUTCOME MEASURE

Digoxin assays per patient day while receiving digoxin (assays/digoxin day), in-hospital mortality, and length of stay were compared before and after implementation of the interventions.

RESULTS

A total of 9468 patients received a digoxin and/or serum digoxin assay. Baseline use of serum digoxin assays was 0.178 assays/digoxin day. Following phase 1, the educational intervention, use declined 20.2% to 0.142 assays/digoxin day (p < 0.03). After phase 2, the implementation of changes in the medical information system, digoxin assay use was maintained at 16.3% less than that at baseline (p < 0.03). Patient mortality was unaffected.

CONCLUSIONS

A low-intensity educational intervention by a clinical pharmacist supplemented by medical information system modification resulted in an important decrease in the use of digoxin assays. The change in physician behavior was sustained for more than 18 months. The model presented is not labor intensive, does not require continuous maintenance by healthcare personnel for a sustained effect, and may be widely applicable to healthcare providers.

Effects of fosinopril on exercise tolerance and clinical deterioration in patients with chronic congestive heart failure not taking digitalis. Fosinopril Heart Failure Study Group

A total of 241 men and women with mild to moderately severe chronic heart failure (New York Heart Association functional class II [90%] or III) and a mean (+/- SD) left ventricular ejection fraction of 25 +/- 7%, entered a 24-week, prospective, double-blind, placebo-controlled trial of 10 or 20 mg/day of fosinopril, a phosphinic acid angiotensin-converting enzyme inhibitor. Patients received concomitant diuretic therapy but not digitalis. Primary end points were mean change in maximal treadmill exercise time and occurrence of prospectively defined clinical events indicative of worsening heart failure (most to least severe): death, withdrawal for worsening heart failure, hospitalization for worsening heart failure, need for supplemental diuretic or emergency room visit for worsening heart failure, and no event. At study end point, treadmill exercise time had improved in the fosinopril versus the placebo group (+28.4 vs -13.5 seconds, p = 0.047). New York Heart Association functional class had improved at end point more frequently (24% vs 13%) and deteriorated less frequently (18% vs 32%) in the fosinopril group (p = 0.003). More patients treated with fosinopril (66% vs 50%) remained free of clinical events indicative of worsening heart failure, and fosinopril-treated patients had less severe clinical events (p = 0.004). Dyspnea, fatigue, and paroxysmal nocturnal dyspnea improved more often and worsened less often in this group (p < or = 0.002), and edema showed a trend toward improvement (p = 0.088). These clinical benefits did not require concomitant digitalis therapy. Fosinopril was associated with an acceptable safety profile.

Problems in determining levels of free digoxin in patients treated with digoxin immune FAb

Determination of free digoxin levels in patients treated with digoxin immune FAb has long been a problematic area in clinical laboratory testing. The older radioimmunoassays resulted in inaccurate and variable results due to the competition of the administered drug with the radioactively labelled forms. The 1995 Physicians' Desk Reference continues to state that digoxin immune FAb will interfere with digitalis immunoassay measurements. This statement, however, is based primarily on the RIA methods. We evaluated the Stratus digoxin assay and the TDX digoxin II assay. Increasing amounts of immune FAb were added in a stepwise fashion to 12 patient samples containing high normal to elevated digoxin levels. Results showed a progressive decrease in digoxin levels when assayed with the Stratus kit. However, five patient samples tested with the TDX kit resulted in constant digoxin values despite the presence of increasing digibind levels. These results suggest that the Stratus method measures free digoxin, whereas the TDX method measures the total digoxin. Measurement of digoxin by the Stratus method is simple and quick. The Stratus digoxin assay may be an accurate and objective way of measuring free digoxin levels in patients on digoxin immune FAb.