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Lack of effect of mizolastine on the safety and pharmacokinetics of digoxin administered orally in repeated doses to healthy volunteers.

The effects of mizolatine, a new H1 receptor antagonist, on safety and pharmacokinetics of digoxin were studied in a double-blind placebo-controlled crossover study. After administration of digoxine alone (0.25 mg o.d. for 7 days), 12 healthy young male volunteers (23+/-2 years) received either placebo and digoxin (0.25 mg o.d.) or mizolastine (10 mg o.d.) and digoxin (0.25 mg o.d.) during 7 days. The assessment criteria consisted in hemodynamic and ECG parameters recordings and the pharmacokinetics of digoxin during the last day of coadministration (day 14). No difference between the 2 treatment groups was evidenced on ECG, hemodynamic, and clinical and laboratory safety parameters. No change in AUC and tmax was recorded. No clinically relevant effect of mizolastine on the digoxin pharmacokinetics was found. However, a statistically significant increase in digoxin Cmax (3.03+/-0.18 nmolxl(-1) vs 2.52+/-0.19 nmolxl(-1), p < 0.05) and Cmin (0.99+/-0.08 nmolxl(-1) vs 0.87+/-0.07 nmolxl(-1), p=0.05) occurred after the coadministration vs digoxin alone. It can be concluded that mizolastine and digoxin at therapeutic dosages can be safely coadministered.

Adult↗

Should we still prescribe digoxin in mild-to-moderate heart failure? Is quality of life the issue rather than quantity?

The recently reported Digitalis Investigation Group (DIG) study has shown that digoxin has no demonstrable effect on survival in heart failure, but may be useful to ameliorate morbidity. The question may be raised whether digoxin is useful for symptomatic improvement in patients with mild or moderate heart failure. A major difficulty in answering this question is the lack of appropriate clinical measures of heart failure that allow a categorization such as mild, moderate and severe heart failure. However, data in several clinical trials permit an approach to this issue in an approximate way. For instance, the DIG study itself indicated that the beneficial clinical effect of digoxin was also apparent in pre-defined subgroups which corresponded to less severe forms of heart failure. The problem with the DIG study in this respect was the lack of direct measures of clinical improvement and the use of what might be taken as surrogates for these; however, it can probably be assumed that digoxin had a beneficial symptomatic effect even in patients with milder forms of heart failure. Direct clinical measures of clinical result were used in the Randomized Assessment of the effect of Digoxin on Inhibitors of ACE Study and the Prospective Randomized Study on Ventricular Failure and the Efficacy of Digoxin. Some inconsistencies between the clinical results of these trials may be explained partly on the basis of sample size, although on the whole the results point to a definite clinical improvement of patients on digoxin therapy, even when heart failure was considered to be mild on the basis of several measurements. Admittedly, the size of the effect of digoxin therapy in these patients may be quite modest. Although some concerns over safety may remain after the DIG trial, it can generally be accepted that digoxin is an effective drug for symptomatic improvement in patients with mild or moderate heart failure. The small size of this effect, however, indicates that the decision to use the drug may well be left to the discretion of the attending physician.

Clinical Trials as Topic↗

Failure of CAVH to remove digoxin-Fab complex in piglets.

Digoxin toxicity may be associated with renal failure and an inability to excrete the digoxin-Fab (antibody fragment) complex used in detoxification. We are unaware of any previous reports regarding the removal of digoxin-Fab fragment complex by continuous arteriovenous hemofiltration. Continuous arteriovenous hemofiltration allows ultrafiltration of molecules less than 50,000 daltons. Because the digoxin-Fab fragment complex has a molecular weight of 45 - 50,000 daltons, we evaluated the efficiency of continuous arteriovenous hemofiltration in removing the digoxin-Fab fragment complex. Three piglets were given 100 mcg/kg digoxin IM, in divided doses. Animals were anesthetized and continuous arteriovenous hemofiltration was begun using a Diafilter 10 cartridge. A mean ultrafiltration rate of 3.6 +/- 0.4 ml/min was obtained. The system equilibrated for 30 minutes and initial serum and ultrafiltrate digoxin levels were obtained. Mean serum values were total 6.20 +/- 1.74 ng/ml and free 3.72 +/- 0.88 ng/ml. Digibind 40 mg IV was given and then samples of serum and ultrafiltrate were obtained at 30, 60 and 90 minutes for digoxin levels. Mean values were as follows: 30 min serum total 54.23 +/- 26.13 ng/ml and free 0.08 +/- 0.08 ng/ml; 60 min serum total 61.24 +/- 27.31 ng/ml and free 0.07 +/- 0.04 ng/ml; and 90 min serum total 67.63 +/- 26.78 ng/ml and free 0.10 +/- 0.10 ng/ml. Ultrafiltrate levels throughout the experiment were negligible (less than or equal to 0.04 ng/ml). Continuous arteriovenous hemofiltration appears to be ineffective in removing the digoxin-Fab fragment complex.

Animals↗

Reevaluation of digoxin-encainide interactions using an animal model.

The effects of intravenous encainide on digoxin-induced atrial ectopic tachycardia (AET) were investigated in the rat using 3-channel simultaneous limb-lead electrocardiography. Pentobarbital-anesthetized (35 mg/kg, intraperitoneal) adult male rats were given digoxin subcutaneously, 30 mg/kg. After onset of AET, rats received either saline (0.5 ml/kg) or encainide; 0.25, 0.5, 1.0, or 2.0 mg/kg intravenously in repeated doses at 15-min intervals. At all doses, encainide converted digoxin-induced AET to ventricular arrhythmias, prolonged recovery time, and increased mortality in comparison to saline-treated animals. An additional group of anesthetized rats was not given digoxin. These animals received encainide (2.0 mg/kg, intravenously) in repeated doses at 15-min interval and developed dose-related increase in the P-R interval only. Blood samples were obtained by cardiac puncture from 12 additional anesthetized, digoxin-treated rats 5 min after the fourth intravenous dose of saline (0.5 ml/kg, n = 6) or encainide (1.0 mg/kg, n = 6). Serum was prepared and analyzed by affinity column-mediated immunoassay. Digoxin levels were the same in both groups. These results suggest that encainide may exacerbate digoxin-induced arrhythmias (proarrhythmic effect) in this species. In view of our findings of digoxin-encainide interactions in the rat, we recommend caution if these drugs are coadministered in humans.

Anilides↗

Effects of digoxin on electrocardiogram in patients with acute atrial fibrillation--a randomized, placebo-controlled study. Digitalis in Acute Atrial Fibrillation (DAAF) Trial Group.

BACKGROUND: Studies of healthy volunteers or patients in sinus rhythm have indicated that treatment with digoxin produces characteristic changes in the electrocardiogram (ECG). No randomized, placebo-controlled studies are available and no study has investigated the effect on ECG in patients with atrial fibrillation. HYPOTHESIS: In a substudy to a trial comparing the therapeutic effect of intravenously administered digoxin with placebo in patients with acute atrial fibrillation, we investigated these effects as well as the relation between ECG changes and serum concentration of digoxin. METHODS: In all, 167 patients were included. Standard ECGs recorded at baseline, and at 2, 6, 12, and 16 h after randomization were digitized, and changes in RR-intervals, QRS width, ST-segment amplitude at 60 ms after the J point, T-wave amplitude, and QTc interval were calculated. Furthermore, the correlation between the serum concentration of digoxin at 16 h after inclusion and changes on the ECG was analyzed. RESULTS: Compared with placebo, digoxin resulted in an increase in RR-interval (p < 0.0001), a decrease in ST-segment and T-wave amplitude (p = 0.009 and p = 0.002, respectively), and in the QTc interval (p = 0.01). These changes were present 2 h after the first dose, but were more pronounced after 16 h. There was no significant correlation between serum concentration of digoxin and ECG changes at 16 h. CONCLUSION: Compared with placebo, digoxin produces significant changes on ECG in patients with acute atrial fibrillation. The changes are in accordance with previous findings in individuals in sinus rhythm. There was no correlation between serum concentration of digoxin and ECG changes.

Acute Disease↗

Relationship between digoxin concentrations in serum and saliva.

The concentration of digoxin in serum and saliva was determined in 18 patients receiving digoxin. Unlike serum, it was necessary to extract saliva with chloroform in order to quantitate digoxin levels accurately. An excellent linear correlation (r = +0.988, p less than 0.001) was observed between the saliva and serum digoxin concentrations. This indicates that saliva digoxin concentrations can be used to monitor digoxin therapy, particularly in patients in whom blood sampling is inconvenient or difficult. The saliva/serum ratio for digoxin concentration was 0.78 plus or minus 0.07 (SD). Since the digoxin binding to plasma proteins is 23%, it is the free drug that is in equilibrium between serum and saliva.

Digoxin↗

Digoxin pharmacokinetics: role of renal failure in dosage regimen design.

Radioimmunoassayed serum concentration and urinary excretion data for digoxin from azotemic patients were characterized using a 2-compartment open model. Urinary excretion rates of digoxin as well as serum concentration data are needed to accurately characterize the disposition of the drug. Seven patients with renal failure showed highly variable steady-state volumes of distribution (V-ss-D equals 195 to 489 liters/1.73 m-minus2) and t1/2beta values (1.5 to 5.2 days). This variability is a major limiting factor in the use of dosage regimen nomograms that assume a constant V-ss-D and a rigorous relationship between t1/2beta and creatinine clearance (Cl-CR). Body clearance (Cl-B) is a parameter that is affected by both elimination and distribution of drugs. A linear relationship between Cl-B and renal clearance of digoxin or Cl-CR was found and was used to develop a model-independent approach to calculation of maintenance doses of digoxin. Several methods for calculating steady-state serum concentrations of digoxin (C-ss-p) were compared with actual measurements obtained in 16 chronically medicated patients. Optimum computation of C-ss-p is obtained by use of digoxin renal and body clearances. Variability in the digoxin:creatinine renal clearance ratio is the major limiting factor in prediction of digoxin dosage regimens.

Adult↗

Digoxin concentration in choroid plexus, brain, and myocardium in old age.

Thirteen aged persons receiving digoxin until the time of death were examined by autopsy, and digoxin concentrations were determined in samples from various tissues (the choroid plexus, grey and white brain matter, left and right ventricular and left and atrial myocardium, diaphragm, and musculus psoas major). These concentrations were related to the digoxin dose and duration of treatment. No significant difference was found between the concentration of digoxin in the choroid plexus and left ventricular myocardium, whereas there were significantly lower concentrations in the right ventricular myocardium and still lower concentrations in the other tissues analyzed. Independent of the digoxin dose, the digoxin concentrations in the choroid plexus tended to be lower in persons treated for a short time before death than in those treated for longer periods of time. Similar differences were not observed in the other tissues, suggesting a slower rate of digoxin uptake in the chroid plexus compared with the myocardium and other tissues. The implications of these findings for the effects of digoxin treatment on the production of cerebrospinal fluid are discussed.

Aged↗

Digoxin-like immunoreactive substances in severe acute liver disease due to viral hepatitis and paracetamol overdose.

The levels of endogenous serum digoxin-like immunoreactive substances were investigated during development of encephalopathy in patients with fulminant hepatic failure. The 67 patients studied had varying degrees of hepatic failure as a result of viral hepatitis or paracetamol overdose. Serum levels of digoxin-like immunoreactive substances were significantly increased in both viral hepatitis and paracetamol overdose, with mean values of 0.42 +/- S.D. 0.25 ng per ml (n = 36) and 0.53 +/- 0.19 ng per ml (n = 31), respectively, as compared to normal control subjects with mean values of 0.01 +/- 0.02 ng per ml (n = 21, p less than 0.001). A statistically significant correlation was found between serum digoxin-like immunoreactive substances and the degree of encephalopathy in the viral hepatitis patients and with the serum creatinine in the paracetamol overdose patients where renal failure was more severe. No correlation was found with liver damage as assessed by the prolongation of the prothrombin time, serum AST or bilirubin values. Experiments with ultrafiltration and heating showed that both free nonprotein-bound digoxin-like immunoreactive substances and the total digoxin-like immunoreactive substances measured were increased. Column chromatography of ultrafiltrates of fulminant hepatic failure serum on Sephadex G-25 demonstrated at least two peaks with digoxin-like immunoreactive activity. Reduced renal function is an important factor in the increased serum level of digoxin-like digoxin-like immunoreactive substances, but their presence due to liver failure, where there is increased permeability of the blood-brain barrier, could be relevant to the development of hepatic encephalopathy.

Acetaminophen↗

Effect of furosemide on serum clearance and renal excretion of digoxin.

Serum turnover and urinary excretion of digoxin with or without oral furosemide were studied in six healthy subjects who received 0.006 mg/kg body weight digoxin intravenously. During furosemide treatment, the total amount of urinary digoxin did not change but the digoxin clearance during the diuretic phase and the digoxin excretion after the diuresis decreased significantly. The average serum half-life was prolonged from 37 hours in the control period to 86 hours in the furosemide period. Decreased glomerular filtration rate by volume depletion might have been responsible for the decreased excretion of digoxin, but there was no significant difference in urine volume after diuresis between the two periods, suggesting the possibility of inhibition of tubular secretion of digoxin by furosemide. It is also possible that serum digoxin concentration may be elevated if furosemide were given more frequently.

Adult↗

Impairment of digoxin clearance by coadministration of quinidine.

Seven healthy volunteers received a single 1.0-mg dose of intravenous digoxin in a drug-free control trial and again during concurrent therapy with therapeutic doses of quinidine. Digoxin kinetics were determined from multiple serum digoxin concentrations measured during 72 hours after dosage. Compared to the control state, quinidine coadministration reduced mean digoxin volume of distribution (15.1 vs. 12.4 l./kg), prolonged its elimination half-life (47.7 vs. 75.7 hours), and significantly reduced total clearance (6.06 vs. 2.18 ml/min.kg). Both renal and extrarenal digoxin clearances were impaired by quinidine. In nine cardiac patients receiving long-term digoxin therapy (0.25 mg twice daily), quinidine coadministration elevated mean morning digoxin levels from 1.37 to 2.0 ng/ml (P less than 0.001) and evening levels from 1.44 to 1.97 ng/ml (N.S.). If digoxin concentrations at the site of action are increased by quinidine, the interaction is likely to be of clinical importance in many patients.

Adult↗

Evaluation of the hypothalamic-pituitary effects of digoxin.

Normally menstruating young female volunteers with no evidence of cardiovascular disease participated in a controlled study of digoxin effects on serum thyroid stimulating hormone (TSH) and prolactin levels in the basal state and after stimulation with thyrotropin releasing hormone (TRH). In the first study, subjects received oral digoxin, 0.5 mg daily, or matching placebo, on days 10 through 22 of a menstrual cycle, then crossed over to placebo or digoxin for days 10 through 22 of the next cycle. Basal serum TSH and prolactin on days 7 through 9 and 20 through 22 did not differ significantly between placebo and digoxin cycles. Levels of both hormones rose after a 200-micrograms intravenous dose of TRH given on days 8 and 21, but the response to TRH did not differ between placebo and digoxin cycles. In the second study, subjects received 0.5 mg intravenous digoxin daily for days 7 through 21 of a menstrual cycle. Basal serum TRH and prolactin did not change significantly in response to digoxin. The findings suggest that hormonal changes associated with digoxin therapy, if they exist, are more likely to reflect direct effects on the target organ rather than indirect effects on the hypothalamic-pituitary axis.

Administration, Oral↗

Methyldopa does not alter the disposition of digoxin.

To investigate whether methyldopa alters digoxin disposition, eight healthy subjects received methyldopa titrated to 250 mg t.i.d. or placebo in a double-blind, cross-over manner for 16 consecutive days, with 0.25 mg intravenous digoxin coadministered on day 5 and 0.25 mg oral digoxin on days 9 to 16. Digoxin concentrations in plasma and urine were measured by RIA. Although assay sensitivity did not allow an adequate assessment of serum AUC(0-infinity) after intravenous administration, mean digoxin AUC(0-24) was 10.2 +/- 3.5 and 10.0 +/- 1.8 ng/ml X hr with placebo and methyldopa, respectively (P greater than 0.05). Mean urinary excretion after digoxin with or without methyldopa treatment was 0.204 +/- 0.34 and 0.197 +/- 0.38 mg, respectively. The mean steady-state serum concentrations of oral digoxin (AUC(0-24)/zeta) with and without methyldopa were 0.65 +/- 0.2 and 0.62 +/- 0.3 ng/ml, respectively. These data revealed no significant differences (P greater than 0.05) for various parameters with power of greater than 0.8 to detect meaningful differences of approximately 30 per cent. Thus, methyldopa did not alter digoxin disposition in healthy subjects, and a pharmacokinetic interaction in patients is unlikely.

Administration, Oral↗

The effect of everyday exercise on steady state digoxin concentrations.

The purpose of this study was to evaluate the effect of 1 hour of everyday exercise (walking at patient's own pace) on serum digoxin concentrations. Nine white male subjects (ages 58-74) who had been taking the same digoxin dose for greater than 1 month participated. There were three continuous phases: 1 hour of rest, 1 hour of exercise, and a final hour of rest. Serum digoxin concentrations were drawn every 20 minutes. During the first rest period, serum digoxin concentrations rose 30% from the first concentration drawn in the study. After 1 hour of exercise, serum digoxin concentrations fell 26.8% from the last concentration of the first rest period. At the end of the second hour of rest, serum digoxin concentrations increased by 36.6% from the last concentration. Repeated measures analysis of variance demonstrated a significant (P less than .01) change in serum digoxin concentrations. Significant (P less than .01) differences were found between sampling times 0 and 60, 60 and 80, 60 and 100, 60 and 120 and 180 minutes using a paired t-test with Bonferroni correction. A weak correlation (r = 0.74, r2 = 0.55) between percent change in concentrations and age during the exercise phase was found, but there was no correlation between the percent change in concentrations and age during the two immobilization phases. Because significant changes in concentrations occurred during each phase of the study, we conclude that the influence of everyday exercise should be taken into account when interpreting serum digoxin concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗

Serum digoxin levels related to plasma propafenone levels during concomitant treatment.

Nine patients with supraventricular rhythm disorders were treated during 5-day periods with different oral doses (300, 450, 600, and 900 mg daily) of propafenone concomitantly to long-term digoxin treatment. A poor correlation (r = .398; P less than .05) was obtained when the difference between the mean digoxin serum level (calculated with the Cmin data determined each of the 5 days) observed during a given propafenone dose and the mean digoxin serum level observed before propafenone treatment, was correlated with the dose of propafenone; but an evident correlation (r = .778; P less than .01) was found when the difference in digoxin level was correlated with the plasma propafenone concentration. The propafenone effect of increasing digoxin blood levels was thus concluded to be poorly dose dependent but strongly concentration dependent. The association of propafenone to a long-term digoxin treatment can be considered with a low risk of toxicity when plasma propafenone concentration does not exceed about 1000 ng/mL. Propafenone plasma levels are unpredictable in view of their wide interindividual variation for a given dose, so their measurement is advised to detect high levels and consequently to prevent a rise in digoxin serum concentrations with the possibility of toxicity. In clinical practice, when propafenone concentration determinations are not readily available, digoxin serum levels at least have to be carefully monitored.

Administration, Oral↗

Digoxin pharmacokinetics and spirapril, a new ace inhibitor.

As concurrent use of digoxin with the novel ACE inhibitor spirapril should be common, potential for spirapril to affect steady-state digoxin kinetics was studied. Fifteen healthy white male volunteers aged 22-42 and weighing 135-225 lbs took digoxin tablets 0.25 mg every 12 hours for 5 weeks. In crossover design, each also received spirapril or matching placebo capsules during weeks 1 and 2, or 4 and 5. Dosage of spirapril was increased from 12 mg to 48 mg once daily. Spirapril produced no significant effect on mean (+/- SD) serum digoxin concentration in the steady state, area under curve for 12 hours, peak digoxin level, time to peak, or urinary digoxin excretion over 12 hours. No change in renal or whole body digoxin clearance was seen. Unlike some other cardiovascular drugs, spirapril does not alter steady-state digoxin kinetics in healthy adults.

Administration, Oral↗

Digoxin pharmacokinetics and perindopril in heart failure patients.

The influence of chronic perindopril treatment on digoxin pharmacokinetics was investigated in 10 patients with mild chronic heart failure under stable diuretic and digitalis treatment and normal renal function. Digoxin was administered at a dose of 0.125 mg/day (n = 2) or 0.250 mg/day (n = 8). The 24-hour steady-state digoxin profile was assessed before and after concomitant administration of perindopril for 1 month at doses of 2 mg once a day for the first 8 days and 4 mg once a day for the remaining 21 days. Chronic treatment with perindopril produced no significant effect on mean (+/- standard deviation) digoxin serum area under the curve for 24 hours (17.9 +/- 7.4 versus 16.3 +/- 4.4 ng/mL.h), peak digoxin concentration (1.3 +/- 0.54 versus 1.2 +/- 0.36 ng/mL), time to peak concentration (3 versus 4 hours), and apparent oral clearance of digoxin (237.7 +/- 109.6 versus 237.4 +/- 79.5 mL/min). Clinical and biologic tolerance of perindopril was good throughout the study. Chronic administration of perindopril did not alter steady-state digoxin kinetics in patients with mild chronic heart failure and normal renal function, indicating that no adaptation of the digoxin dose is required during co-prescription with perindopril in such patients.

Aged↗

Intersubject variation in absorption of digoxin in normal volunteers.

The absorption of oral digoxin preparations was evaluated following single-dose administration of 0.5 mg of digoxin to 16 normal volunteers in a randomized crossover design. Absorption was estimated using the cumulative excretion of digoxin in urine for 7 days and the area under the 24-hr serum digoxin concentration curve (AUC). Significant intersubject variability was observed with both parameters, but this variability was greater for the AUC. After intravenous administration, the 7-day digoxin excretion was 68% of the dose. The elixir and a rapid dissolution tablet were significantly better absorbed (84.5 and 77.8%, respectively) than was a slow dissolution tablet (66.7%), as reflected by the fraction of the amount excreted in the urine following intravenous administration of the same dose. There was a highly significant correlation between the cumulative digoxin excretion in urine during the first 2 days compared to 7 days (r = +0.972,p less than 0.001). Bioavailability of oral digoxin preparations can be reliably determined by comparison of the cumulative 2-day excretion of digoxin following a single dose.

Administration, Oral↗