Enzalutamide and analytical interferences in digoxin assays

Significant Improvement in Digoxin Immunoassays Over Four Decades: Newer Assays are Less Affected by Interferences

BACKGROUND

Digitalis glycosides derived from foxglove plants have been used for medicinal purposes since the 16th century. Currently, digoxin derived from foxgloves is used clinically. Owing to the narrow therapeutic range, therapeutic drug monitoring is essential; however, digoxin immunoassays suffer from interference.

METHODS

The issue of interference was reviewed for both older polyclonal antibody-based digoxin assays and newer monoclonal antibody-based digoxin assays. A literature search was conducted using PubMed, ScienceDirect, Scopus, Web of Science, and ResearchGate for studies on digoxin immunoassays published in the English language from 1969 to the present.

RESULTS

Radioimmunoassays for digoxin in the 1970s and, later, first-generation nonradioimmunoassay methods were liable to several interferences, including digoxin-like immunoreactive substances, spironolactone, potassium canrenoate, and various digoxin metabolites. However, for the last 10-15 years, next next-generation digoxin immunoassays have been virtually free from such interferences. Nevertheless, certain herbal supplements, as well as both Digibind and DigiFab, interfere with serum digoxin measurement, even with the more recently developed digoxin assays.

CONCLUSIONS

More recently introduced monoclonal antibody-based digoxin assays are superior to the older polyclonal antibody-based digoxin assays.

Quality by design with design of experiments approach for development of a stability-indicating LC method for enzalutamide and its impurities in soft gel dosage formulation

A novel ultra-performance liquid chromatographic (UPLC) method has been developed and approved for the quantitative determination of enzalutamide (ENZ) and its impurities in drug product dosage form by applying the quality by design with design of experiments approach. An efficient chromatographic separation was achieved on a Waters ACQUITY CSH C₁₈ (100 × 2.1 mm × 1.7 μm) column in gradient elution mode. A mixture of potassium phosphate monobasic buffer and acetonitrile (10 mm, adjusted to pH 4.0 with 1% orthophosphoric acid) at a flow rate of 0.2 mL min^-1 (column temperature at 40°C) under ultraviolet detection at 270 nm was used for quantitation. The peak resolution among ENZ and its impurities (Impurity-1, Impurity-2, Impurity-3, Impurity-4, Impurity-5, Impurity-6 and Impurity-7) was greater than 2.5. Regression analysis confers an R² value (correlation coefficient) higher than 0.999 for the active substance and impurities. The detection level for ENZ impurities was at a level below 0.015% (0.12 μg/mL). The accuracy levels for different compounds were close to 100%. The inter- and intra-day precisions for ENZ and impurities were evaluated and their relative standard deviation (%) values were less than 3.5. Our results show that the UPLC-UV stability-indicating method will be an essential tool that could determine the drug product's impurities and be useful in regular quality control and stability studies of the ENZ drug product dosage form.

[Adverse drug reactions profiles for abiraterone and enzalutamide: A pharmacovigilance descriptive analysis]

OBJECTIVE

The aim of this study was to describe the profile of adverse drug reactions (ADRs) observed with abiraterone and enzalutamide, based on cases registered in the French regional pharmacovigilance centres to identify potential pharmacovigilance signals.

METHODS

We extracted from the French pharmacovigilance database all cases of ADRs or drug interactions involving abiraterone or enzalutamide from the time they market authorization date until December 31st, 2017. Signal detection results have been transmitted by the French Agency for Health Products (ANSM). The data were compared with those of the risk management plans for each drug and the literature.

RESULTS

Among the 233 observations analyzed, nearly 62% involved abiraterone as a suspect drug and 38% involved enzalutamide; only 1 case involved both drugs. The ADRs profile is different between the drugs. Abiraterone is mostly associated with expected cardiac diseases (heart failure, and QT prolongation), expected with the drug. Also described, several cases of hepatotoxicity have been reported, however some cases with fatal outcome suggest that despite a follow-up of the liver function tests, it is difficult to anticipate this risk. Signals concerning acute renal failure and ischemic stroke have arisen. Enzalutamide is more particularly associated with various neurological disorders (convulsions, hallucinations, fatigue, and memory impairment) expected with the drug. While ischemic heart disease is also expected, signals of heart failure and atrial fibrillation have arisen. A potential hepatotoxicity of the molecule is discussed because of cases of cholestatic hepatitis.

CONCLUSION

The analysis of the French pharmacovigilance database cases allows to confirm an expected and monitored risk profile in the risk management plan for both drugs. Several signals have arisen, some of which will be investigated through a pharmacoepidemiology study.

Is androgen deprivation therapy for prostate cancer associated with cardiovascular disease? A meta-analysis and systematic review

BACKGROUND

Androgen deprivation therapy (ADT) is widely being applied in men who suffered from prostate cancer. Whether androgen deprivation therapy (ADT) is associated with an increased risk of developing cardiovascular-related disease is poorly defined.

OBJECTIVES

The aim of the present meta-analysis is to explore the relationship between ADT and the risk of cardiac events. MATERIALS AND METHODS: For this systematic review and meta-analysis, we searched databases from inception to April 2019 for randomized controlled trials (RCT) or observational studies that reported data on ADT administration and cardiac event incidence. The connection was evaluated through estimating relative risk ratio (RR) and 95% confidence intervals (CIs).

RESULTS

A significantly increased acute myocardial infarction (AMI) was detected in the ADT group compared with the control group (RR = 1.19, 95% confidence interval (CI), 1.02-1.39, P < .05). A significant difference between cardiovascular disease (CVD) and ADT was also observed, with summary RR = 1.25, 95% CI, 1.11-1.40, P < .05. Furthermore, our study also suggested ADT was not related to increased incidence of sudden cardiac death (SCD) (RR = 1.13, 95% CI, 0.92-1.38, P = .24); AMI and CVD were not connected with the duration of ADT (AMI: RR = 1.31; 95% CI, 0.66-2.63, P = .44, for > 5 year group; CVD: RR = 1.12, 95% CI, 0.97-1.30, P = .12, for > 5 year group). In addition, the RR for risk of CVD was 1.28 (95% CI, 1.01-1.62, P < .05) for men with PCa on new hormonal agents.

DISCUSSION

Various ADT modalities have different impact on cardiovascular disease risk in different level. Long-term application of ADT is not associated with increased risk of AMI and CVD. Both abiraterone and enzalutamide could significantly increase the incidence of cardiac events in patients who suffered from prostate cancer. Cautions and periodic cardiovascular elevation are necessary for patients before the ADT starting.

CONCLUSIONS

Androgen deprivation therapy is associated with increased risk of AMI, CHD, in contrast, this association is not detected in SCD.

Crataegus mexicana (Tejocote) Exposure Associated with Cardiotoxicity and a Falsely Elevated Digoxin Level

INTRODUCTION

A species of hawthorn, Crataegus mexicana (tejocote), has been marketed as a weight-loss supplement that is readily available for purchase online. While several hawthorn species have shown clinical benefit in the treatment of heart failure owing to their positive inotropic effects, little is known about hawthorn, and tejocote in particular, when consumed in excess. We describe a case of tejocote exposure from a weight-loss supplement resulting in severe cardiotoxicity.

CASE REPORT

A healthy 16-year-old girl presented to an emergency department after ingesting eight pieces of her mother's tejocote root weight-loss supplement. At arrival, she was drowsy, had active vomiting and diarrhea, and had a heart rate of 57 with normal respirations. Her initial blood chemistries were unremarkable, except for an elevated digoxin assay of 0.7 ng/mL (therapeutic range 0.5-2.0 ng/mL). All other drug screens were negative. She later developed severe bradycardia and multiple episodes of hypopnea that prompted a transfer to our institution, a tertiary pediatric hospital. Her ECG demonstrated a heart rate of 38 and Mobitz type 1 second-degree heart block. She was subsequently given two vials of Digoxin Immune Fab due to severe bradycardia in the setting of suspected digoxin-like cardiotoxicity after discussion with the regional poison control center. No clinical improvement was observed. Approximately 29 hours after ingestion, subsequent ECGs demonstrated a return to normal sinus rhythm, and her symptoms resolved.

DISCUSSION

Tejocote root toxicity may cause dysrhythmias and respiratory depression. Similar to other species of hawthorn, tejocote root may cross-react with some commercial digoxin assays, resulting in a falsely elevated level.