Dosing of dabigatran etexilate in relation to renal function and drug interactions at a tertiary hospital

Real-World Analysis of Potential Pharmacokinetic and Pharmacodynamic Drug Interactions with Apixaban in Patients with Non-Valvular Atrial Fibrillation

Purpose

We conducted this study to assess the real-world prevalence, nature, predictors, and clinical necessity of apixaban pharmacokinetic (PK) and pharmacodynamic (PD) drug interactions in patients with non-valvular atrial fibrillation (NVAF) at a tertiary medical institution in Saudi Arabia.

Patients and Methods

An observational retrospective cohort analysis was conducted in adult patients diagnosed with NVAF receiving apixaban for stroke prevention from the period of June 2015 to May 2019.

Results

Of the 1271 patients included in the analysis, 611 (48.1%) patients had potential PD– or PK–drug interactions with apixaban. Of those, 490 (38.6%) patients had potential PD drug–drug interactions (DDIs) and 121 (9.5%) patients had potential PK-DDIs. PD-DDIs with apixaban were mainly with antiplatelet therapy followed by non-steroidal anti-inflammatory drugs and antidepressants. PK-DDIs with apixaban were mainly with combined P-gp/CYP3A4 inhibitors or inducers. History of minor bleeding was positively correlated with PD-DDIs with apixaban, ß coefficient = 0.455 (OR 1.58; 95% CI 1.01–2.45); p<0.05. History of acute coronary syndrome was positively correlated with PD-DDIs with apixaban, ß coefficient = 0.515 (OR 1.60; 95% CI 1.36–1.99); p<0.05. History of heart failure was positively correlated with PK-DDIs with apixaban, ß coefficient = 0.459 (OR 1.58; 95% CI 1.07–2.35); p<0.05. Almost 15% of the included patients had no clinical indication to receive the potential interacting drug with apixaban and about 20% of them were assuming an inappropriate apixaban dose according to the product package insert.

Conclusion

Pharmacodynamics and pharmacokinetics interactions are common in more than half of the patients with NVAF receiving apixaban for stroke prevention in this real-world analysis. Some of these interacting medications are not indicated. Drug–drug interactions should always be considered and monitored with apixaban with a regular assessment of the need for any interacting medication.

Potential drug-drug interactions with direct oral anticoagulants in elderly hospitalized patients

Background

To determine the prevalence and nature of potential drug-drug interactions (DDIs) with direct oral anticoagulants (DOACs) in elderly hospitalized patients.

Methods

This was a retrospective observational study. Inclusion criteria were: aged over 65 years; taking apixaban, rivaroxaban or dabigatran; and admitted to the Repatriation General Hospital between April 2014 and July 2015. A list of clinically relevant 'perpetrator' drugs was compiled from product information, the Australian Medicines Handbook, the Australian National Prescribing Service resources, and local health network guidelines. The prevalence and nature of potential DDIs with DOACs was determined by comparing inpatient drug charts with the list of perpetrator drugs.

Results

There were 122 patients in the study with a mean age of 82 years. Most patients had nonvalvular atrial fibrillation and were taking DOACs to prevent thrombotic stroke (83%). Overall, 45 patients (37%) had a total of 54 potential DDIs. Thirty-five patients had potential pharmacodynamic DDIs with antidepressants, nonsteroidal anti-inflammatory drugs and antiplatelets (35/122, 29%). Nineteen patients had potential pharmacokinetic DDIs (19/122, 16%). Of these, 68% (13/19) were taking drugs that increase DOAC plasma concentrations (amiodarone, erythromycin, diltiazem or verapamil) and 32% (6/19) were taking drugs that decrease DOAC plasma concentrations (carbamazepine, primidone or phenytoin). There were no cases of patients taking contraindicated interacting drugs.

Discussion

Potential DDIs with DOACs in elderly hospital inpatients are relatively common, particularly interactions that may increase the risk of bleeding. The risk-benefit ratio of DOACs in elderly patients on polypharmacy should always be carefully considered.

Estimated glomerular filtration rate calculated using different creatinine and cystatin based formulas in prediction of trough plasma Dabigtran concentration

BACKGROUND

In this paper we evaluated the relationship between trough DAB concentration with eGFR calculated using CRE and CYS based formulas.

MATERIALS AND METHODS

We considered 100 patients. eGFR was calculated using CKD-EPIcreat, CG, MDRD, CKD-EPIcys and CKD-EPIcombined equations. DAB dosage was selected on the basis of CKD-EPIcreat and relationship between trough DAB concentration and eGFRs was evaluated.

RESULTS

Trough DAB concentration roughly correlates with eGFR calculated using various formulas. CKD-EPIcreat eGFR was higher than CKD-EPIcys. In patients receiving a DAB dosage considered adequate using CKD-EPIcreat eGFR but considered excessive using CKD-EPIcys, we observed higher DAB trough concentration and an increased prevalence of subjects with drug concentration >200ng/mL.

CONCLUSION

These results suggest that eGFR alone was unable to fully explain trough DAB plasma concentration. Therefore a drug's prescription schedule based on eGFR only should be inadequate. We observed a better correlation between trough DAB concentration and CKD-EPIcys rather than CKD-EPIcreat eGFR. Thus, in patients chronically treated with DAB for thromboprophylaxis in nonvalvular atrial fibrillation evaluation of eGFR using a cystatin base formula should be considered.

Prescribing of Direct Oral Anticoagulants in Atrial Fibrillation Based on Estimation of Renal Function Using Standard and Modified Cockcroft-Gault Equations: A Retrospective Analysis

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Evaluation of the chromogenic anti-factor IIa assay to assess dabigatran exposure in geriatric patients with atrial fibrillation in an outpatient setting

Background

Dabigatran etexilate may be underutilized in geriatric patients because of inadequate clinical experience in individuals with severe renal impairment and post-marketing reports of bleeding events. Assessing the degree of anticoagulation may improve the risk:benefit ratio for dabigatran. The aim of this prospective study was to identify whether therapeutic drug monitoring of dabigatran anticoagulant activity using a chromogenic anti-factor IIa assay is a viable option for therapy individualization.

Methods

Plasma dabigatran concentration was assessed in nine patients with nonvalvular atrial fibrillation aged 75 years or older currently receiving dabigatran etexilate for prevention of stroke, using an anti-factor IIa chromogenic assay and HPLC-MS/MS. Trough concentrations were evaluated on two separate occasions to determine intrapatient variation.

Results

Blood was collected at 13.1 ± 2.3 h (mean ± SD) post dose from patients prescribed dabigatran etexilate 150 mg twice daily (5/9 patients) or dabigatran etexilate 75 mg twice daily (4/9 patients). Results from the anti-factor IIa chromogenic assay correlated with dabigatran concentrations as assessed by HPLC-MS/MS (r² = 0.81, n = 16). There was no correlation between dabigatran trough values taken at separate visits (r² = 0.002, n = 7). Furthermore, there was no correlation found between the drug concentrations and patients’ renal function determined by both creatinine and cystatin-C based equations. None of the patients enrolled in the study were in the proposed on-therapy trough range during at least one visit.

Conclusion

The chromogenic anti-factor IIa assay demonstrated similar performance in quantifying dabigatran plasma trough concentrations to HPLC-MS/MS. Single measurement of dabigatran concentration by either of two methods during routine visits may not be reliable in identifying patients at consistently low or high dabigatran concentrations.

Electronic supplementary material

The online version of this article (doi:10.1186/s12959-016-0084-2) contains supplementary material, which is available to authorized users.

A proposal for dose-adjustment of dabigatran etexilate in atrial fibrillation guided by thrombin time

Dabigatran is an oral anticoagulant that is increasingly used for atrial fibrillation (AF). Presently, many authorities state that routine laboratory coagulation monitoring is not required. However, data have recently been published demonstrating that higher trough plasma dabigatran concentrations are associated with lower thromboembolic and higher haemorrhagic event rates. Using these data, we simulate a range of AF patients with varying risks for these events and derive a target range of trough plasma dabigatran concentrations (30-130 μg l(-1) ). Finally, we propose that a conventional screening coagulation assay, the thrombin time (TT), can be used to discern whether or not patients are within this range of dabigatran concentrations.

Correlation between trough plasma dabigatran concentrations and estimates of glomerular filtration rate based on creatinine and cystatin C

AIMS

Dabigatran is largely cleared by renal excretion. Renal function is thus a major determinant of trough dabigatran concentrations, which correlate with the risk of thromboembolic and haemorrhagic outcomes. Current dabigatran dosing guidelines use the Cockcroft-Gault (CG) equation to gauge renal function, instead of contemporary equations including the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations employing creatinine (CKD-EPI_Cr), cystatin C (CKD-EPI_Cys) and both renal biomarkers (CKD-EPI_CrCys).

METHODS

A linear regression model including the dabigatran etexilate maintenance dose rate, relevant interacting drugs and genetic polymorphisms (including CES1), was used to analyse the relationship between the values from each renal function equation and trough steady-state plasma dabigatran concentrations.

RESULTS

The median dose-corrected trough steady-state plasma dabigatran concentration in 52 patients (38-94 years) taking dabigatran etexilate was 60 µg/L (range 9-279). The dose-corrected trough concentration in a patient on phenytoin and phenobarbitone was >3 standard deviations below the cohort mean. The CG, CKD-EPI_Cr, CKD-EPI_Cys and CKD-EPI_CrCys equations explained (R (2), 95 % CI) 32 % (9-55), 37 % (12-60), 41 % (16-64) and 47 % (20-69) of the variability in dabigatran concentrations between patients, respectively. One-way analysis of variance (ANOVA) comparing the R (2) values for each equation was not statistically significant (p = 0.74).

DISCUSSION

Estimates of renal function using the four equations accounted for 32-47 % of the variability in dabigatran concentrations between patients. We are the first to provide evidence that co-administration of phenytoin/phenobarbitone with dabigatran etexilate is associated with significantly reduced dabigatran exposure.