Digoxin Clearance Research Articles

Population Pharmacokinetics of Digoxin in Nonagenarian Patients: Optimization of the Dosing Regimen.

The aim of this study was to develop a population pharmacokinetic model of digoxin in patients over 90 years old and to propose an equation for adjusting digoxin dose in this population. We included 326 nonagenarian patients admitted to Severo Ochoa University Hospital (Spain) who received digoxin and were under therapeutic drug monitoring. All data were retrospectively collected, and population modeling was performed with non-linear mixed-effect modeling software (NONMEM®). One- and two-compartment models were tested to calculate digoxin clearance (Cl), volume of distribution (Vd), absorption rate constant (Ka), and bioavailability (bioavailable fraction, F). The covariates were evaluated by stepwise covariate model building, and the final model was internally validated by bootstrap analysis with 1000 resamples. External validation was performed with another population of 95 patients with the same characteristics as the modeling group. The population was 26% males, with a mean age of 93.2 years (90-103 years), mean creatinine 1.11 mg/dL (0.42-3.81 mg/dL), and mean total body weight 61.2 kg (40-100 kg). The pharmacokinetics of digoxin were best described by a one-compartment model (ADVAN2 TRANS2), with first-order conditional estimation with interaction. The covariates with influence on our model were creatinine clearance based on the Cockcroft-Gault equation (CG), serum potassium (K), co-administration of loop diuretics, and sex: Cl/F = 4.55 · (CG/36.4)0.468 · 0.83LD · 1.21SEX; Vd/F = 355 · (K/4.3)-0.849; Ka = 1.22 h-1 [where LD indicates loop diuretics (1 for administered, 0 for otherwise) and SEX indicates patient sex (1 for male, 0 for female)]. Based on our results, we proposed an equation to adjust the digoxin dosing regimen in nonagenarian patients: dose (mg) = 0.144 · (CG/36.4)0.468 · 0.83LD · 1.21SEX. The greatest influence on digoxin clearance came from renal function calculated by the Cockcroft-Gault equation. Vd was decreased by K. The model developed showed a precise predictive performance to be applied for therapeutic drug monitoring.

Potential Effects of Digoxin on Renal Functions in Patients With Congestive Heart Failure.

Renal dysfunction is a common complication among patients with congestive heart failure (CHF) and can significantly impact their management, especially when medications like digoxin are involved. The clearance of digoxin is closely tied to the glomerular filtration rate (GFR), which suggests that the safety and efficacy of digoxin may vary with renal function. Therefore, this study aimed to assess the potential effects of digoxin on renal function in patients diagnosed with CHF at a tertiary hospital in the Asir region of Saudi Arabia. A retrospective study examined the records of 30 CHF patients treated with digoxin. Renal function markers like estimated GFR (eGFR), creatinine, blood urea nitrogen (BUN), albumin, and urine levels were compared before and after digoxin treatment. Liver enzymes and other relevant parameters were also examined. A statistical analysis using t-tests was conducted to evaluate the changes in renal function indicators before and after digoxin treatment. The mean eGFR decreased significantly from 65.4 ± 8.9 mL/min/1.73m2 before digoxin to 57.7 ± 7.8 mL/min/1.73m2 after (p = 0.001). Creatinine, BUN, albumin, and urine levels showed no significant changes. Digoxin significantly increased aspartate aminotransferase (AST) from 34.5 ± 11.6 U/L to 53.8 ± 14.6 U/L (p = 0.002), alanine aminotransferase (ALT) from 38.5 ± 12.6 U/L to 55.3 ± 17.6 U/L (p = 0.013), and creatine kinase from 117.7 ± 22.5 U/L to 133.9 ± 15.8 U/L (p = 0.012). Hemoglobin decreased significantly from 12.8 ± 1.4 g/dL to 12.1 ± 1.4 g/dL (p = 0.034). No significant changes occurred in myoglobin, troponin, bilirubin, platelets, potassium, calcium, or chloride levels. Effects on kidney function did not differ significantly by gender or age, except blood urea nitrogen was higher in patients over 50 years (8.3 ± 2.3 vs. 5.6 ± 2.7 mg/dL, p = 0.015). This study suggests digoxin may adversely affect renal function in CHF patients, as evidenced by reduced eGFR. However, the small retrospective design limits definitive conclusions. Further prospective research with larger samples is warranted to elucidate digoxin's renal effects in CHF patients.

Influence of Weight and Body Size on the Pharmacokinetics of Heart Failure Pharmacotherapy: A Systematic Review.

To conduct a review of studies evaluating the influence of body size and weight (WT) on the pharmacokinetics (PK) of drugs recommended for heart failure (HF) treatment. A systematic search of the MEDLINE (1946 to April 2023) and EMBASE (1974 to April 2023) databases was conducted for articles that focused on the impact of WT or body size on the PK of drugs of interest used in HF patients. Articles written in English or French related to the aim of our study were retained for analysis. Of 6493 articles, 20 were retained for analysis. Weight was associated with the clearance of digoxin, carvedilol, enalapril, and candesartan as well as the volume of distribution of eplerenone and bisoprolol. There was no documented direct impact of WT on the PK of furosemide, valsartan, and metoprolol, although these studies were limited or confounded by the small sample size, adjustment of PK factors by WT, or the use of the Cockroff-Gault equation for the evaluation of creatinine clearance, which includes WT. This review highlights and summarizes the available data on the importance of WT on the PK of HF treatment. Considering the significant impact of WT on most HF drugs in this review, it may be important to further investigate it in the context of personalized therapy, particularly in patients presenting extreme WTs.

Novel Explanted Human Liver Model to Assess Hepatic Extraction, Biliary Excretion and Transporter Function.

Realistic models predicting hepatobiliary processes in health and disease are lacking. We therefore aimed to develop a physiologically relevant human liver model consisting of normothermic machine perfusion (NMP) of explanted diseased human livers that can assess hepatic extraction, clearance, biliary excretion, and drug-drug interaction (DDI). Eleven livers were included in the study, seven with a cirrhotic and four with a noncirrhotic disease background. After explantation of the diseased liver, NMP was initiated. After 120 minutes of perfusion, a drug cocktail (rosuvastatin, digoxin, metformin, and furosemide; OATP1B1/1B3, P-gp, BCRP, and OCT1 model compounds) was administered to the portal vein and 120 minutes later, a second bolus of the drug cocktail was co-administered with perpetrator drugs to study relevant DDIs. The explanted livers showed good viability and functionality during 360 minutes of NMP. Hepatic extraction ratios close to in vivo reported values were measured. Hepatic clearance of rosuvastatin and digoxin showed to be the most affected by cirrhosis with an increase in maximum plasma concentration (Cmax ) of 11.50 and 2.89 times, respectively, compared with noncirrhotic livers. No major differences were observed for metformin and furosemide. Interaction of rosuvastatin or digoxin with perpetrator drugs were more pronounced in noncirrhotic livers compared with cirrhotic livers. Our results demonstrated that NMP of human diseased explanted livers is an excellent model to assess hepatic extraction, clearance, biliary excretion, and DDI. Gaining insight into pharmacokinetic profiles of OATP1B1/1B3, P-gp, BCRP, and OCT1 model compounds is a first step toward studying transporter functions in diseased livers.

Effects of multiple doses of montmorillonite, alone and in combination with activated charcoal, on the toxicokinetics of a single dose of digoxin in rats.

A narrow margin between the therapeutic and toxic doses of digoxin can result in an increased incidence of toxicity. Since digoxin has an enterohepatic cycle, multiple oral doses of absorbents like montmorillonite may be useful in the treatment of digoxin toxicity. In this study, 4 groups of 6 rats received intraperitoneal digoxin (1 mg/kg), and half an hour later, distilled water (DW) or oral adsorbents, including montmorillonite (1 g/kg), activated charcoal (1 g/kg) (AC) alone or in combination in the ratio of 70:30. Half of the mentioned doses were also gavaged at 3 and 5.5 hr after digoxin injection. The serum level of digoxin, biochemical factors, and activity score were assessed during the experiment. Three control groups only received DW, montmorillonite, or AC. All adsorbents were able to significantly decrease the serum level of digoxin compared to the digoxin+DW group (P<0.01). Only montmorillonite reversed the digoxin-induced hyperkalemia (P<0.05). Multiple dose administration of adsorbents also significantly reduced the digoxin area under the curve and half-life and increased digoxin clearance (P<0.05). However, there was no significant difference in the kinetic parameters between groups that received digoxin plus adsorbents. Multiple-dose of montmorillonite reversed digoxin toxicity and reduced serum digoxin levels by increasing the excretion and reducing the half-life. Montmorillonite has also corrected digoxin-induced hyperkalemia. Based on the findings, a multiple-dose regimen of oral montmorillonite could be a suitable candidate for reducing the toxicity issue associated with drugs like digoxin that undergo some degree of enterohepatic circulation.

Evaluating the regulation of transporter proteins and P-glycoprotein in rats with cholestasis and its implication for digoxin clearance.

BACKGROUNDCardiac and hepatic functionality are intertwined in a multifaceted relationship. Pathologic processes involving one may affect the other through a variety of mechanisms, including hemodynamic and membrane transport effects.AIMTo better understand the effect of extrahepatic cholestasis on regulations of membrane transporters involving digoxin and its implication for digoxin clearance.METHODSTwelve adult rats were included in this study; baseline hepatic and renal laboratory values and digoxin pharmacokinetic (PK) studies were established before evenly dividing them into two groups to undergo bile duct ligation (BDL) or a sham procedure. After 7 d repeat digoxin PK studies were completed and tissue samples were taken to determine the expressions of cell membrane transport proteins by quantitative western blot and real-time polymerase chain reaction. Data were analyzed using SigmaStat 3.5. Means between pre-surgery and post-surgery in the same experimental group were compared by paired t-test, while independent t-test was employed to compare the means between sham and BDL groups.RESULTSDigoxin clearance was decreased and liver function, but not renal function, was impaired in BDL rats. BDL resulted in significant up-regulation of multidrug resistance 1 expression in the liver and kidney and its down-regulation in the small intestine. Organic anion transporting polypeptides (OATP)1A4 was up-regulated in the liver but down-regulated in intestine after BDL. OATP4C1 expression was markedly increased in the kidney following BDL.CONCLUSIONThe results suggest that cell membrane transporters of digoxin are regulated during extrahepatic cholestasis. These regulations are favorable for increasing digoxin excretion in the kidney and decreasing its absorption from the intestine to compensate for reduced digoxin clearance due to cholestasis.

Population pharmacokinetic analysis and dosage recommendations for digoxin in Japanese patients with atrial fibrillation and heart failure using real-world data

BackgroundDigoxin is an important treatment option for reducing the ventricular rate in patients with atrial fibrillation (AF) and heart failure (HF). Digoxin has a narrow therapeutic window and large interindividual variability. A low target blood concentration, especially ≤0.9 ng/mL, is recommended for patients with HF who are taking digoxin. This study aimed to develop a population pharmacokinetic model and to identify clinical factors that affect digoxin exposure and an optimal digoxin dosing regimen in Japanese patients with AF and HF.MethodsA population pharmacokinetic analysis was performed by using a nonlinear mixed effects model based on 3465 concentration points from 391 patients (>18 years) who were receiving oral digoxin. Using trough serum digoxin concentrations and clinical data, a population pharmacokinetic model was developed for determining covariates of clearance. A 1-compartment model was used to examine the interindividual variability of the oral clearance (CL/F) of digoxin. An appropriate dosage of digoxin was identified using Monte Carlo simulation.ResultsThe final model demonstrated that creatinine clearance (CLCR) and the use of amiodarone were factors that contributed to the CL/F of digoxin. Monte Carlo simulation results showed that with a daily maintenance dose of 0.25 mg, the intoxication risk window of a trough serum concentration of ≥0.9 ng/mL could be reached in more than half of patients regardless of renal function category or concurrent use of amiodarone. The appropriate maintenance dosage was 0.125 mg daily for most Japanese patients with AF and HF. However, with a daily dose of 0.125 mg, a trough serum concentration of ≥0.9 ng/mL could be reached in more than half of patients with renal impairments (CLCR 30 mL/min) or concurrent use of amiodarone. A daily maintenance dose of 0.0625 mg was acceptable for these patients.ConclusionsCLCR and the use of amiodaron were found to contribute to digoxin clearance using a population pharmacokinetic methodology. For Japanese patients with AF and HF, 0.125 mg is an appropriate daily digoxin maintenance dose, but a dose reduction is required for patients with CLCR <30 mL/min or concurrent amiodarone use.

Evaluating plasma Digoxin concentration after an intravenous loading dose in patients with renal failure

Background: Digoxin is a medication of Glycoside family which is commonly prescribed for patients with atrial fibrillation, atrial flutter, and heart failure. With a narrow therapeuticlevel(0.5–2 ng/mL), careful monitoring of digoxin blood level is necessary. Symptoms of digoxin toxicity include nausea, vomiting, visual changes, altered mental status, hyperkalemia, and cardiovascular collapse. As renal failure decreases the clearance of digoxin, and impaired renal function is common in heart failure, this population is at higher risk of toxicity. Methods & materials: In this prospective study, patients with chronic kidney disease- nondialysis (CKD-ND) who were admitted with heart failure or atrial fibrillation at university hospital, were enrolled. Digoxin-naive patients were treated with a 10 mcg/kg intravenous digoxin loading dose. Serum digoxin level was measured 6 to 12 hours after the last loading dose. Patients were followed for 48 hours for signs of toxicity. Correlation between therapeutic digoxin level and degree of renal failure was evaluated. The effect of serum electrolyte (magnesium, calcium, and potassium) concentration on digoxin level was determined. Pregnant women were excluded from study. Results: From 2018 to 2020, 87 CKD patients, (60 (69%) men and 27 (31%) women) aged from 31 to 92 years old, with a mean age of 70.51 ± 14.06 years were admitted to the cardiac unit. Near 80% of the cohort were CKD stage 3 and 4 patients. About half of patients had digoxin levels in therapeutic range (45 cases = 51.7%), followed by 24.1% with supra therapeutic and the other 24.1% with toxic levels. There was significant relationship between GFR and serum digoxin concentration (p-value = 0.038); the lower the GFR was, the higher was the digoxin level and also between serum creatinine and digoxin level (p value: .04). Serum digoxin concentration had significant correlation with serum magnesium level (p-value = 0.006). Conclusion: this study demonstrated that monitoring plasma Digoxin concentration after an intravenous loading dose in patients with renal failure can be very helpful to prevent digoxin toxicity. The lower the GFR was, the higher the digoxin level and the risk for toxicity if the bolus and even maintenance do not monitor meticulously.

Drug Elimination Alteration in Acute Lymphoblastic Leukemia Mediated by Renal Transporters and Glomerular Filtration.

Drug elimination alteration has been well reported in acute lymphoblastic leukemia (ALL). Considering that transporters and glomerular filtration influence, to different extents, the drug disposition, and possible side effects, we evaluated the effects of ALL on major renal transporters and glomerular filtration mediated pharmacokinetic changes, as well as expression of renal drug transporters. ALL xenograft models were established and intravenously injected with substrates of renal transporters and glomerular filtration separately in NOD/SCID mice. The plasma concentrations of substrates, after single doses, were determined using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). With the development of ALL, protein expression of MDR1, OAT3 and OCT2 were increased by 2.62-fold, 1.70-fold, and 1.45-fold, respectively, whereas expression of MRP2 and MRP4 were significantly decreased by 30.98% and 45.28% in the kidney of ALL groups compared with control groups. Clearance of MDR1-mediated digoxin, OAT3-mediated furosemide, and OCT2-mediated metformin increased by 3.04-fold, 1.47-fold, and 1.26-fold, respectively. However, clearance of MRPs-mediated methotrexate was reduced by 39.5%. These results are consistent with mRNA expression. Clearance of vancomycin and amikacin, as markers of glomerular filtration rate, had a 2.14 and 1.64-fold increase in ALL mice, respectively. The specific alteration of renal transporters and glomerular filtration in kidneys provide a rational explanation for changes in pharmacokinetics for ALL.

2019 AGS Beers Criteria for older adults

2019 AGS Beers Criteria for older adults

Organic Anion Transporting Polypeptide 1a4 is Responsible for the Hepatic Uptake of Cardiac Glycosides in Mice.

Among organic anion transporting polypeptide (Oatp) family transporters expressed in the rodent liver, such as Oatp1a1, Oatp1a4, Oatp1b2, and Oatp2b1, Oatp1a4 has a unique character to recognize neutral cardiac glycosides as a substrate in addition to organic anions. The relative contribution of Oatp1a4 to the substrate uptake into hepatocytes has not been clarified. In this study, we investigated the importance of Oatp1a4 in the hepatic uptake of its substrate drugs using Slco1a4-/- mice. The hepatic mRNA expression of Slco1a4 was decreased significantly in Slco1a4-/- mice, whereas no differences were seen in other hepatic transporters between wild-type and Slco1a4-/- mice. We determined the plasma concentrations and liver-to-plasma concentration ratios (Kp,liver) of Oatp1a4 substrates, including ouabain, digoxin, BQ-123, fexofenadine, rosuvastatin, pravastatin, nafcillin, and telmisartan, after continuous intravenous infusion. The plasma concentrations of ouabain and rosuvastatin were 2.1-fold and 1.7-fold higher in Slco1a4-/- mice, and Kp,liver of ouabain and digoxin were 13.4-fold and 4.3-fold lower in Slco1a4-/- mice, respectively. Furthermore, the biliary clearance of ouabain and digoxin with regard to plasma concentration were 21.9-fold and 4.1-fold lower in Slco1a4-/- mice, respectively, accompanied with a marked reduction in their Kp,liver, whereas the systemic clearance of ouabain, but not digoxin, was reduced significantly in Slco1a4-/- mice. These results suggest that Oatp1a4 plays a major role in the hepatic accumulation of cardiac glycosides in mice.

Delineating the Role of Various Factors in Renal Disposition of Digoxin through Application of Physiologically Based Kidney Model to Renal Impairment Populations.

Development of submodels of organs within physiologically-based pharmacokinetic (PBPK) principles and beyond simple perfusion limitations may be challenging because of underdeveloped in vitro-in vivo extrapolation approaches or lack of suitable clinical data for model refinement. However, advantage of such models in predicting clinical observations in divergent patient groups is now commonly acknowledged. Mechanistic understanding of altered renal secretion in renal impairment is one area that may benefit from such models, despite knowledge gaps in renal pathophysiology. In the current study, a PBPK kidney model was developed for digoxin, accounting for the roles of organic anion transporting peptide 4C1 (OATP4C1) and P-glycoprotein (P-gp) in its tubular secretion, with the aim to investigate the impact of age and renal impairment (moderate to severe) on renal drug disposition. Initial PBPK simulations based on changes in glomerular filtration rate (GFR) underestimated the observed reduction in digoxin renal excretion clearance (CLR) in subjects with moderately impaired renal function relative to healthy. Reduction in either proximal tubule cell number or the OATP4C1 abundance in the mechanistic kidney model successfully predicted 59% decrease in digoxin CLR, in particular when these changes were proportional to reduction in GFR. In contrast, predicted proximal tubule concentration of digoxin was only sensitive to changes in the transporter expression/ million proximal tubule cells. Based on the mechanistic modeling, reduced proximal tubule cellularity and OATP4C1 abundance, and inhibition of OATP4C1-mediated transport, are proposed as possible causes of reduced digoxin renal secretion in renally impaired patients.

Lack of effect of ezogabine/retigabine on the pharmacokinetics of digoxin in healthy individuals: results from a drug-drug interaction study.

IntroductionThe potential for ezogabine/retigabine (EZG/RTG) and its N-acetyl metabolite (NAMR) to inhibit the transporter protein P-glycoprotein-(P-gp)-mediated digoxin transport was tested in vitro. EZG/RTG did not inhibit P-gp. However, NAMR inhibited P-gp in a concentration-dependent manner. Based on these in vitro results, NAMR had the potential to inhibit P-gp at therapeutic doses of EZG/RTG (600–1,200 mg/day). As digoxin has a narrow therapeutic index, inhibition of digoxin clearance may have an impact on its safety.MethodsAn open-label, single-center, two session, fixed-sequence study was conducted to assess the effect of co-administration of therapeutic doses of EZG/RTG on digoxin pharmacokinetics in healthy adults. In session 1, subjects received a single dose of digoxin 0.25 mg. In session 2, EZG/RTG was up-titrated over 6 weeks. Digoxin 0.25 mg was co-administered at EZG/RTG steady-state doses of 600, 900, and, based on tolerability, 1,050/1,200 mg/day. Blood samples were collected over 144 hours for determination of digoxin, EZG/RTG, and NAMR concentrations. Urine samples were collected over 48 hours for determination of digoxin concentrations.ResultsOf 30 subjects enrolled, 29 were included in the pharmacokinetic analysis. Compared with digoxin alone, co-administration with EZG/RTG led to small increases in the digoxin plasma area under the concentration–time curve (AUC)0–120 at doses of 600, 900, and 1,050/1,200 mg (geometric mean ratio 1.08, 90% confidence interval [CI] 1.01–1.15; 1.18, 90% CI 1.10–1.27; 1.13, 90% CI 1.05–1.21, respectively). Safety was consistent with previous repeat-dose studies of EZG/RTG in healthy subjects.ConclusionCo-administration of EZG/RTG across the therapeutic range resulted in small, non-dose-dependent and non-clinically relevant increases in digoxin systemic exposure, suggesting that digoxin dose adjustment is not necessary.

Efficiency of individual dosage of digoxin with calculated concentration.

BackgroundDigoxin is a frequently prescribed drug, particularly in the elderly population, in which there is an increased prevalence of atrial fibrillation and cardiac failure. With its complex pharmacokinetic profile and narrow therapeutic index, use of digoxin requires regular monitoring of blood levels. Recent evidence suggests that a lower concentration range (0.4–1.0 ng/mL) is preferable in patients with congestive heart failure and a higher range (0.8–2.0 ng/mL) is needed in patients with atrial tachyarrhythmia. The Konishi equation is widely used to predict the serum digoxin concentration (SDC) in Japan. This study assessed the correlation between SDC predicted by the Konishi equation and that actually measured in Chinese patients and investigated the impact of renal function on SDC.MethodsThe study subjects comprised 72 patients with cardiac failure or/and atrial tachyarrhythmia seen at our hospital from January 2012 to December 2013. The patients were divided into five groups according to Kidney Diseases Outcome Quality Initiative guidelines. SDCs were measured using the Abbott Architect i1000 immunology analyzer. The correlations between measured SDCs and calculated SDCs and between clearance of digoxin and creatinine clearance rate were assessed retrospectively.ResultsThe correlation between measured and predicted SDC calculated by the Konishi equation was significant (r=0.655, P<0.001) for the 72 patients overall; however, correlations within the different stages of renal function were nonsignificant, with a correlation found only in patients with stage 3 (30 mL per minute < creatinine clearance <60 mL per minute). With regard to the correlation between clearance of digoxin and creatinine clearance, our results show that although there was a significant correlation between clearance of digoxin and creatinine clearance in the group overall, correlations were not evident within the different stages of renal function.ConclusionThe results of this study indicate that clearance of digoxin and the creatinine clearance rate cannot be explained by renal function alone and that the validity of the Konishi equation for individualizing the digoxin dosage in Chinese patients is limited, being applicable only in stage 3 renal disease. Further research in larger numbers of patients across all stages of renal function will be required in the future to verify the original Konishi model.

Chronic Digoxin Toxicity Precipitated by Dronedarone

To report the case of a patient who presented with chronic symptoms attributable to dronedarone-induced digoxin toxicity. A review of the literature is also provided. This case report details a case of a 77-year-old male patient who presented to the hospital with multiple ambiguous symptoms that lasted several weeks. The patient was later hospitalized for symptoms of chronic digoxin toxicity, including prolonged nausea, diarrhea, weakness, and lack of appetite. The patient had a long history of digoxin use for control of his atrial fibrillation but experienced signs and symptoms of toxicity only after the addition of dronedarone. Both the Naranjo and Drug Interaction Probability Scales indicated a "probable" relationship between the development of digoxin toxicity and dronedarone. Due to a p-glycoprotein-mediated interaction, dronedarone is able to decrease the renal clearance of digoxin, thus putting patients at risk for potentially fatal digoxin toxicity. This is the second case report detailing dronedarone-induced digoxin toxicity and the first to focus on chronic digoxin toxicity. The presentation, possible causes, and drug-drug interactions associated with digoxin toxicity are described. This report aims to increase clinicians' awareness of this possible complication. It is recommended that digoxin be discontinued prior to initiating dronedarone. If concomitant therapy is absolutely necessary, the dose of digoxin should be halved prior to initiating dronedarone. Digoxin plasma levels should be monitored closely, with frequent patient evaluation for signs and symptoms of digoxin toxicity.

Population Pharmacokinetic Analysis of Digoxin in Chinese Neonates and Infants

To obtain more information regarding the influence of various covariates on the disposition of digoxin in Chinese neonates and infants, routine clinical pharmacokinetic data were retrospectively collected from 131 hospitalized patients. A nonlinear mixed effects modeling (NONMEM) method was applied to the data. A one-compartment/first-order absorption model was employed to estimate the influence of total body weight (allometric power model), postnatal age, serum creatinine, gender, presence of heart congestive failure, and concomitant medications on apparent total clearance and apparent drug distribution of digoxin. Pharmacokinetic parameter estimates for CL/F and V/F were 0.147 L∙h(-1)∙kg(-1) and 15.7 L/kg, respectively. Total body weight and postnatal age were identified as the important factors affecting total clearance of digoxin; total body weight was the covariate identified to influence the apparent distribution volume. Both internal (bootstrap method, visual predictive checks, and normalized prediction distributed error) and external validation supported the stable and predictive performance of the final model. We concluded that the model can be used to choose an appropriate dose regimen in Chinese neonates and infants.

Dronedarone-Induced Digoxin Toxicity

Dronedarone is a relatively new antiarrhythmic drug approved for paroxysmal or persistent atrial fibrillation. Dronedarone can inhibit P-glycoprotein-mediated digoxin clearance and increase steady-state digoxin level 2.5 times. It is important to closely monitor plasma digoxin levels or administer a lower loading dose of digoxin in patients taking dronedarone concomitantly. We report a case of digoxin toxicity in a patient taking concomitant dronedarone as a result of interaction between digoxin and dronedarone.

A pharmacokinetic interaction study of ticagrelor and digoxin in healthy volunteers

Ticagrelor is a reversibly binding P2Y12 receptor antagonist for the prevention of atherothrombotic events in patients with acute coronary syndrome. Previous in vitro studies showed that ticagrelor is a substrate and inhibitor of P-glycoprotein (ABCB1). Therefore, we examined the potential interaction between digoxin, a P-glycoprotein substrate, and ticagrelor by evaluating the pharmacokinetics, safety, and tolerability. This was a randomized, double-blind, two-period crossover study in healthy volunteers (n = 20). Pharmacokinetic parameters of digoxin and ticagrelor were evaluated following co-administration of ticagrelor 400 mg qd or placebo on days 1-16, and digoxin (0.25 mg bid on day 6 and 0.25 mg qd on days 7-14). Co-administration of ticagrelor increased the digoxin maximum plasma concentration by 75 %, from 1.8 ng/ml to 3.0 ng/ml (Gmean ratio [GMR] 1.75 [95 % CI, 1.52-2.01]); minimum plasma concentration by 31 %, from 0.5 ng/ml to 0.7 ng/ml (GMR 1.31, 1.13-1.52); and mean area under the curve by 28 %, from 16.8 ng · h/ml to 21.0 ng · h/ml (GMR 1.28, 1.12-1.46), compared with placebo. Renal clearance of digoxin was unaffected by the presence of ticagrelor. Digoxin had no effect on the pharmacokinetics of ticagrelor or its active metabolite, AR-C124910XX. Co-administration of ticagrelor and digoxin was well tolerated. Collectively, these results indicate that ticagrelor is a weak inhibitor of the P-glycoprotein transporter. Based on these findings, it is recommended that serum concentrations of drugs like digoxin (P-glycoprotein transporter substrates with a narrow therapeutic range) are monitored when initiating or changing ticagrelor therapy.

Therapeutic Drug Monitoring and Population Pharmacokinetics of Digoxin in Jordanian Patients

Therapeutic monitoring of digoxin and the population pharmacokinetic parameters in Jordanian patients were done. Fifty three patients visited cardiac department of Jordan University hospital participated in this study, thirty two patients had congestive heart failure (CHF), while twenty one patients had atrial fibrillation (AF). Ninety three blood samples were collected from those patients for the measurement of digoxin level using AxSYM digoxin II assay method. Serum creatinine and potassium levels were also measured, in addition to blood pressure and heart rate. Microsoft Excel and Statistica programs were used for kinetic and statistical analysis. NONMEM computer program ADVAN 4 and 2 compartment model was used for population analysis of digoxin parameters. The serum digoxin level ranged from 0.11-4 ng/ml. The percentage of all patients enrolled in this study that were out of therapeutic range was 49.05%. Serum digoxin levels were out of therapeutic range in 53.12% of patients with CHF and 42.85% in those with AF. The pharmacokinetic parameters for digoxin obtained in this study using traditional methods were: creatinine clearance CLcr (89.78 ± 45.61 ml/min), digoxin actual clearance CL (200.57 ± 154.52 L/day), volume of distribution V (541.57 ± 149.87L), t1/2(2.98 ± 2.05 day), elimination rate constant (0.41± 0.396 day-1). A strong correlation was also found between actual digoxin clearance with log dose normalized (R2=0.999), and t1/2 (R2= 0.875). No correlations were found between the log of the normalized dose and other pharmacokinetic parameters or potassium levels. The population pharmacokinetic parameter for digoxin obtained in this study were: CL (3.34L/h), Vc (3.27L), Vt (123L), inter-compartment clearance Q (72L/h), absorption rate constant KA (1.25h-1). In Jordanian patients with either AF or CHF digoxin dose adjustment based on therapeutic drug monitoring principles is recommended. Digoxin pharmacokinetics were similar to those reported in non-Jordanian patients; estimated population pharmacokinetic parameters were in agreement with literature values.

A Simplified Protocol Employing Elacridar in Rodents: A Screening Model in Drug Discovery to Assess P-gp Mediated Efflux at the Blood Brain Barrier

In the present study we have developed a simple, time, and cost effective in vivo rodent protocol to screen the susceptibility of a test compound for P-glycoprotein (P-gp) mediated efflux at the blood brain barrier (BBB) during early drug discovery. We used known P-gp substrates as test compounds (quinidine, digoxin, and talinolol) and elacridar (GF120918) as a chemical inhibitor to establish the model. The studies were carried out in both mice and rats. Elacridar was dosed intravenously at 5 mg/kg, 0.5 h prior to probe substrate administration. Plasma and brain samples were collected and analyzed using UPLC-MS/MS. In the presence of elacridar, the ratio of brain to plasma area under the curve (B/P) in mouse increased 2, 4, and 38-fold, respectively, for talinolol, digoxin, and quinidine; whereas in rat, a 70-fold increase was observed for quinidine. Atenolol, a non P-gp substrate, exhibited poor brain penetration in the presence or absence of elacridar in both species (B/P ratio ~ 0.1). Elacridar had no significant effect on the systemic clearance of digoxin or quinidine; however, a trend towards increasing volume of distribution and half life was observed. Our results support the utility of elacridar in evaluation of the influence of P-gp mediated efflux on drug distribution to the brain. Our protocol employing a single intravenous dose of elacridar and test compound provides a cost effective alternative to expensive P-gp knockout mice models during early drug discovery. Keywords: Blood brain barrier, Brain to plasma ratio, Digoxin, Elacridar, P-glycoprotein, Pharmacokinetics, Quinidine