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Nasal absorption of digoxin in rats.

The nasal administration of digoxin was studied in rats and compared to intravenous, intraduodenal and rectal administration of the drug. The results indicated that the plasma level of digoxin after nasal administration was comparable to the level after intravenous injection. Administration by the intraduodenal and rectal routes resulted in considerably lower plasma levels. These data reveal that digoxin absorption across the nasal membranes is a reasonable approach. In the in situ nasal and intestinal perfusion experiments, digoxin disappeared from the perfusate following the apparent first-order kinetics. The nasal and intestinal absorption rate of digoxin was reduced by an increase in the perfusion volume. The plot of absorption rate constant against 1/volume resulted in a straight line, suggesting that digoxin is absorbed from nasal mucosa by a passive diffusion process.

Absorption↗

Trapidil does not affect serum levels and cardiotonic action of digoxin in healthy humans.

The influence of trapidil on serum levels and cardiac effects of digoxin was investigated in 10 healthy men, intraindividually compared with placebo. Each subject took digoxin orally for 9 days (0.375 mg daily on days 1 to 8, 0.25 mg on day 9) either combined with trapidil (400 mg daily on days 1 to 8, 200 mg on day 9) or combined with placebo in a cross-over design. Trapidil failed to change significantly the steady-state serum digoxin concentrations on day 9 of treatment. It did also not alter significantly the following digoxin effects: shortening in QS2c time indicating the cardiotonic digoxin effect, shortening in QTc time, increase in PTQ index. But trapidil prevented the negative chronotropic digoxin effect.

Adult↗

Neutralization of free digoxin-like immunoreactive components of oriental medicines Dan Shen and Lu-Shen-Wan by the Fab fragment of antidigoxin antibody (Digibind).

Dan Shen and Lu-Shen-Wan, traditional Chinese medicines used as remedies for heart diseases, demonstrate digoxin-like immunoreactivity. The digoxin-like immunoreactive components of Lu-Shen-Wan show approximately 55% protein binding, while Dan Shen demonstrates concentration-dependent protein binding (68% bound at lower concentrations but only 25% bound at higher concentrations). Because Dan Shen and Lu-Shen-Wan can cause substantial toxic effects in patients, we studied the potential use of Digibind (Fab fragment of polyclonal antidigoxin antibody; Burroughs Wellcome, Research Triangle Park, NC) for neutralizing the pharmacologically active free fractions of Dan Shen and Lu-Shen-Wan. Drug-free serum pools were supplemented with Dan Shen or Lu-Shen-Wan to achieve apparent digoxin concentrations expected in severe overdoses. Aliquots of supplemented serum pools were supplemented further with aqueous Digibind solution to achieve final Digibind concentrations between 5 and 20 microg/mL (expected in vivo range in patients overdosed with digoxin and being treated with Digibind). We observed complete removal of the free apparent digoxin in the presence of Digibind for Dan Shen and Lu-Shen-Wan. Digibind binds free digoxin-like immunoreactive components of Dan Shen and Lu-Shen-Wan in vitro.

Bufanolides↗

A critical appraisal of a further three new commercial digoxin radioimmunoassay kits with reference to cross-reacting substances.

A further 3 digoxin radioimmunoassay (RIA) kits have been evaluated for performance and cross-reaction with digitoxin, spironolactone, canrenone and furosemide (Lasix-Hoechst). Effects of serum protein concentrations have also been tested. The kits tested were from the following manufacturers: A) Diagnostic Products Corporation Digoxin RIA Kit. B) Byk-Mallinckrodt SPAC Digoxin Kit. C) Boehringer-Mannheim Digoxin RIA Kit. All kits used a 125I-labelled tracer. Kit A used a conventional liquid phase system using double-antibody separation for bound and free drug, Kits B and C used a solid-phase antibody coated tube method. All kits showed a lower cross-reaction to digitoxin than quoted by the manufacturer. Cross-reaction to spironolactone (Aldactone--Boehringer-Mannheim) was less than 1.50 nmol/l at a serum concentration of 125 mg/l Aldactone in all 3 kits. The cross-reaction to canrenone was somewhat higher, 5.2 nmol/l "digoxin" being measured in one kit at a serum canrenone concentration of 125 mg/l. There was no cross-reaction with furosemide in any kit, even at a serum concentration of 5 g/l. The coated-tube assays were affected by serum albumin and globulin concentration changes, one kit showing a difference of over 50% binding in the range 1--20% albumin. The double-antibody kit did not show dependence on the concentration of these proteins. All kits measured digoxin with good reproducibility in the range 0.40--10.0 nmol/l.

Blood Proteins↗

Enhanced sensitivity to digoxin in dystrophic mice.

We estimated the effect of digoxin on the myocardial potassium content and the action potentials of the left ventricular papillary muscles in dystrophic mice (C57BL/6JCL dy X dy). All of 10 dystrophic mice died following ip injection of digoxin at a dose of one quarter of the iv LD50 for normal mice. The myocardial digoxin concentration and the myocardial potassium content in dystrophic mice were similar to those in normal mice before and 60 min after the ip injection of digoxin. The action potential durations (APD) in dystrophic mice were significantly longer than those in normal mice. Perfusion of digoxin (2 micrograms/ml) for 30 min reduced the APD significantly and induced arrhythmias in dystrophic mice, but it did not bring about any significant change in normal mice. These data suggest that dystrophic mice have increased sensitivity to digitalis. This hypersensitivity to digitalis is not due to increased myocardial digoxin uptake or decreased myocardial potassium content.

Action Potentials↗

Effects of digoxin on blood pressure responses to norepinephrine, angiotensin II and vasopressin in conscious rats.

To investigate the interaction of cardiac glycosides with vasoconstrictors, we examined the effects of short term treatment with the cardiac glycoside digoxin (6 mg/kg/day, i.p., for 6 days) in rats made hypertensive by chronic infusion of norepinephrine (NE), angiotensin II (A II) or vasopressin (VP). When digoxin was administered simultaneously with NE at 1.8 mg/kg/day (i.p.) by use of osmotic minipumps in conscious rats, systolic blood pressure decreased to 120 +/- 3 mmHg on Day 1 whereas it rose to 148 +/- 2 mmHg in rats given NE alone (p less than 0.01). The antihypertensive effect of digoxin was sustained for the entire experimental period and was not associated with any change in urinary sodium excretion. When the same dose of digoxin was administered simultaneously with A II at 900 micrograms/kg/day (i.p.) in conscious rats, systolic blood pressure rose to a greater extent than in those given A II alone. The administration of digoxin had no effect on the blood pressure elevation induced by chronic infusion of VP at a rate of 7.2 U/kg/day (i.p.). It is concluded that short term treatment with digoxin has a variety of effects on blood pressure in rats; pressor, depressor, or is no effects depending upon vasoconstrictor used.

Angiotensin II↗

Clinical pharmacokinetics of digoxin in infants.

Based on clinical experience, infants with congestive heart failure are given larger doses of digoxin than adults, whether calculated on the basis of body weight or surface area. The reasons for this difference in dosage are not clear. The myocardium of the infants might be more resistant to the effects of digoxin than that of adults, and/or differences might exist between infants and adults concerning the absorption, distribution and elimination of the glycoside. Infants have been found to absorb digoxin in solution at the same rate and to the same extent as adults. The relative distribution of the glycoside to different tissues is also similar in the two age-groups. However, the binding of digoxin to several tissues seems to be more extensive in infants than in adults. In agreement with this, the apparent volume of distribution of the glycoside is larger in infants than in adults. As no enhanced urinary excretion has been found in infants there might be a non-renal elimination of the glycoside. With most prevailing dose schedules for digoxin, serum concentrations higher than those considered optimum for adults are often obtained in infants. It is known that infants tolerate higher serum digoxin concentrations than adults without developing signs of toxicity. However, it is not known whether such high concentrations are necessary for obtaining an adequate inotropic effect on the myocardium of the infants. If the relation between serum concentration and effect is the same in infants and adults, the loading (digitalising) dose generally given to infants is unnecessarily high.

Absorption↗

Haemoperfusion in the management of digoxin toxicity: is it warranted?

Several recent publications have encouraged the use of hemoperfusion to remove digoxin from the body of overdosed patients. The usefulness of haemoperfusion in removing digoxin from the body has therefore been examined using pharmacokinetic simulation techniques and published data. Haemoperfusion for a period of 4 hours with a clearance of 100 ml/min removes less than 7% of the amount of digoxin in the body (including that in the gastrointestinal tract at the beginning of haemoperfusion), regardless of the time after the dose that haemoperfusion is started. Dramatic therapeutic benefit in digoxin intoxication is unlikely to be a consequence of the amount of digoxin removed from the body by haemoperfusion. If therapeutic benefit is derived from a transient decline of digoxin concentration in plasma, it may be expected to be negated as the drug redistributes from tissues.

Digoxin↗

Absence of interaction of fondaparinux sodium with digoxin in healthy volunteers.

OBJECTIVE: Fondaparinux sodium is the first of a new class of antithrombotic agents: the selective factor Xa inhibitors. Coadministration with digoxin may occur in clinical practice and both drugs are excreted almost completely by the renal route. In this study we assessed the possible pharmacokinetic and pharmacodynamic interaction of fondaparinux sodium with digoxin at steady state in healthy male volunteers. DESIGN: In a phase I randomised, crossover study, volunteers (n = 24) were treated in two periods. The first period was once-daily administration of fondaparinux sodium 10mg subcutaneously alone for 7 days; the second period was 7 days of digoxin 0.25mg orally alone followed by 7 days of coadministration with fondaparinux sodium 10mg. Each period was separated by a washout of 12 days. METHODS: Urinary volumes, plasma concentration-time profiles and noncompartmental pharmacokinetic parameters of fondaparinux sodium and digoxin were obtained at steady state, following administration alone or together for each period. A bioequivalence approach was taken to assess interaction. Pharmacodynamic parameters were supine blood pressure and heart rate and the ECG parameters PR interval, QRS interval, QT interval and QT(c). The safety of the treatments was monitored. RESULTS AND CONCLUSIONS: The pharmacokinetic profiles of both digoxin and fondaparinux sodium were unaffected by coadministration. Bioequivalence was concluded, based on the 90% confidence intervals of the ratio of adjusted geometric means calculated for the 2-by-2 comparison of peak concentration, area under the concentration-time curve and cumulative urinary excretion, which lay within the 0.80 to 1.25 reference interval. There were no clinically significant fluctuations in vital signs and ECG parameters. The coadministration of digoxin with fondaparinux sodium was well tolerated and no significant changes were observed in vital signs.

Adolescent↗

Angiotensin converting enzyme inhibitors versus digoxin for the treatment of congestive heart failure.

Angiotensin converting enzyme (ACE) inhibition and digoxin may be used in the management of heart failure. Digoxin increases myocardial contractility in vitro, and has a modest but durable beneficial effect in congestive heart failure due to impaired left ventricular systolic function. ACE inhibitors have clear beneficial effects in all grades of heart failure and, in addition, modify the natural history and reduce mortality. Comparative studies in mild to moderate heart failure reveal a tendency towards greater benefits and tolerability of ACE inhibitors over digoxin. ACE inhibition is indicated, in conjunction with diuretic therapy, for all grades of heart failure. Digoxin is best reserved for patients with atrial fibrillation and a rapid ventricular response, and for those whose heart failure is not controlled with an ACE inhibitor plus a diuretic. In patients with heart failure following myocardial infarction, digoxin is of modest benefit. Digoxin should be administered slowly and carefully to avoid acute vasoconstriction and toxicity. Provisional data suggest ACE inhibitors are also beneficial in these patients. However, the results of clinical trials presently in progress are required to clarify their role following myocardial infarction.

Angiotensin-Converting Enzyme Inhibitors↗

A clinical assessment of the potential for pharmacological interaction between nimesulide and digoxin in patients with heart failure.

The potential interaction between nimesulide, a nonsteroidal anti-inflammatory drug, and digoxin was studied in 9 patients [6 males, 3 females; mean age 67 (range 57 to 70) years] with mild heart failure. All patients were receiving maintenance therapy with digoxin (0.25 mg/day, orally) and were treated with oral nimesulide 100mg twice daily for 7 days. Blood samples were collected at 8am and 6pm for 4 days before and throughout the nimesulide treatment period for determination of serum digoxin concentrations. Physical health, electrocardiographic recordings and blood and urine samples were also monitored. Mean serum digoxin concentrations remained within the normal therapeutic range throughout the study despite large interindividual variation. Furthermore, there were no significant differences between the morning and afternoon serum digoxin concentrations and there was no major change in the clinical condition of any patient. These results indicate that short term administration (7 days) of conventional therapeutic doses of nimesulide (100mg twice daily) does not modify the serum digoxin profile in patients with low class heart failure treated with a maintenance dose (0.25 mg/day) of this cardiac glycoside.

Aged↗

Digoxin use in congestive heart failure. Current status.

The use of digitalis in congestive heart failure with normal sinus rhythm is still debated. While older uncontrolled, withdrawal studies from 1969 to 1983 provided incomplete data, with poorly documented clinical status and poor haemodynamic and exercise data, some patients did improve clinically when digitalis treatment was utilised. Randomised, double-blind, placebo-controlled trials from 1977 to 1991 were of better quality but still short in duration, with small sample sizes and still with incomplete haemodynamic and exercise data. In 1993, the Prospective Randomised Study of Ventricular Failure and Efficacy of Digoxin (PROVED) and Randomised Assessment of Digoxin on Inhibitors of the Angiotensin-Converting Enzyme (RADIANCE) study, followed in 1997 by the Digitalis Investigation Group (DIG) trial, documented that digoxin prevents clinical deterioration and hospitalisations, and improves exercise tolerance and left ventricular function, but has no effect on survival. A substudy of the DIG trial showed no detrimental effect of digoxin on survival in patients with ejection fraction (EF) of > 45%, i.e. left ventricular (LV) diastolic dysfunction. Therefore, digoxin appears to be the first inotrope with no detrimental effect on survival in heart failure. In addition, the neurohormonal effect of digoxin has been documented, and is possibly present with dosages even lower than 0.25 mg. Finally, it has been determined that patients with only mild heart failure do obtain documented benefit from administration of this drug.

Angiotensin-Converting Enzyme Inhibitors↗

Verapamil-digoxin interaction in chronic hemodialysis patients.

Verapamil increases the serum-digoxin concentration (SDC) in digoxin treated normals due to a compromised renal and extrarenal clearance. In chronic hemodialysis patients (CHD-patients) treated with digoxin where the renal elimination is diminished, verapamil has been shown to cause substantial increases of SDC with risk of digoxin intoxication. The effect of verapamil treatment on SDC in 8 nearly anephric (Uvol less than 1 l/d) CHD-patients on digoxin treatment was assessed. The patients were continuously treated with verapamil for two periods of two weeks at two dosage levels, 120 mg/d and 240 mg/d, whereafter verapamil was withdrawn. SDC and serum-verapamil were measured weekly. The SDC increased from 1.1 mmol/l to 1.7 mmol/l (p less than 0.05, N = 7) during the first two weeks. Increasing the dose of verapamil to 240 mg/d did not cause a further increment in SDC; on the contrary, the mean SDC decreased. The SDC increments varied between 0 and 200% of baseline values. We conclude that verapamil treatment decreases digoxin clearance in CHD-patients and that the influence of verapamil on SDC in CHD-patients shows great interindividual variation with no close dose dependency and decreases to pretreatment level in 2-3 weeks.

Adult↗

Comparison of digoxin analysis by high-performance liquid chromatography/post-column derivatization and fluorescence polarization immunoassay.

1. This study compared the analysis of digoxin using a high-performance liquid chromatographic post-column derivatization (HPLC-PC) assay and the TDx fluorescence polarization immunoassay (FPIA). 2. Serum obtained from 15 digitalized patients showed higher mean digoxin levels with the FPIA method as compared to the HPLC-PC procedure such that the mean HPLC-PC/FPIA ratio was 0.91 +/- 0.14 (mean +/- SD). Demonstrated cross-reactivity of digoxin metabolites with the FPIA is probably responsible for this observation. 3. Cross-reactivity of the immunoassay towards endogenous material present in serum samples from certain patient groups was an even greater problem, with apparent 'digoxin' serum concentrations in untreated hepatic failure patients being within the therapeutic range for digoxin. 4. The HPLC-PC method did not suffer from such interference and would therefore provide more accurate values for patients where high levels of interference could contribute to false digoxin levels.

Chromatography, High Pressure Liquid↗

Magnesium sulfate in the treatment of ventricular arrhythmias due to digoxin toxicity.

Although digoxin antibodies are the definitive treatment of cardiac arrhythmias due to digoxin toxicity, magnesium can also be effective especially with low serum magnesium levels. The case report describes a patient with digoxin toxicity, ventricular tachycardia and a slightly elevated serum magnesium. Two 10 mmol doses of intravenous magnesium sulfate were associated with a more stable junctional rhythm with bigeminy. Magnesium is known to suppress early after depolarizations, and in supraphysiological doses, may act as an indirect antagonist of digoxin at the sarcolemma Na(+)-K(+)-ATPase pump. Intravenous magnesium may be used to treat cardiac arrhythmias due to digoxin poisoning where there is likely to be a delay in the availability of digoxin antibodies, even in the presence of elevated serum magnesium.

Aged↗

Population pharmacokinetics of digoxin in Korean patients.

AIM: Digoxin possesses a narrow therapeutic index and shows a large inter-patient pharmacokinetic variability. The purpose of this study was to develop a population model for the pharmacokinetics of digoxin in Korean patients. METHODS: Plasma concentrations of digoxin after multiple administration at varying dosing schedules in Korean patients were used for population modeling. Data analysis was performed with the P-Pharm software. The data were best fitted by a one-compartment model. The effect of demographic and clinical factors like sex, age, weight, disease state, and renal function on the pharmacokinetic parameters of digoxin was investigated. RESULTS: The study indicated that the clearance of digoxin was influenced by creatinine clearance, while body weight and creatinine clearance were the covariates for its volume of distribution. The population mean estimates for CL and V were 4.4 l/h and 535 l, respectively. Absorption rate constant was lower in females and in the presence of concomitant drug treatment. CONCLUSION: A population pharmacokinetic model for the digoxin pharmacokinetics in a section of Korean patients was developed. The relationships between the pharmacokinetic parameters and the demographic data and the patient-specific covariates were established.

Adult↗

The effect of quinidine and other oral antiarrhythmic drugs on serum digoxin. A prospective study.

We compared the effects of quinidine and three alternate antiarrhythmic drugs on serum digoxin concentration in 63 patients before and during administration of quinidine, procainamide, disopyramide, or mexiletine. Quinidine increased digoxin concentration by at least 0.5 nmol/L in 21 of 22 patients: Mean serum digoxin rose from 1.2 nmol/L to 2.4 nmol/L (P less than 0.001). Procainamide, disopyramide, or mexiletine increased serum digoxin by 0.5 nmol/L in one of 41 patients. Anorexia, nausea, and vomiting develop soon after starting quinidine therapy in 10 of the 22 patients who received quinidine but in only five of the 41 patients who received procainamide, disopyramide, or mexiletine (P less than 0.01). Quinidine prolonged the PR intervals from 160 +/- 14 ms to 183 +/- 26 ms, but procainamide, disopyramide, and mexiletine did not change the PR interval (P less than 0.005). In digitalized patients, quinidine increases serum digoxin concentration, increases digoxin's effect on atrioventricular conduction, and produces more adverse gastrointestinal effects than procainamide, disopyramide, or mexiletine.

Aged↗

Effects of quinidine on serum digoxin concentration: a prospective study.

Results of studies of 15 adults placed on quinidine therapy after their serum digoxin concentrations were stabilized showed significantly increased digoxin concentrations. The average digoxin concentration before quinidine therapy was 0.75 +/- 0.28 ng/mL and after 4 days of quinidine therapy was 1.41 +/- 0.43 ng/mL. During this period, the renal clearance of digoxin decreased from 53.4 +/- 21 mL/min . 1.73 m to 35.3 +/- 12.6 mL/ min . 1.73 m. No significant correlation was found between the individual rise in serum digoxin concentrations and the rise in serum quinidine concentrations. These results suggest that serum digoxin concentration should be monitored closely for at least the first 4 days of quinidine therapy.

Aged↗