Investigation of the effects of physiological and vasodilation-induced autonomic activation on the QTc Interval in healthy male subjects

Use of antihistamines and risk of ventricular tachyarrhythmia: a nested case-control study in five European countries from the ARITMO project

PURPOSE

After regulatory restrictions for terfenadine and astemizole in '90s, only scarce evidence on proarrhythmic potential of antihistamines has been published. We evaluate the risk of ventricular tachyarrhythmia (VA) related to the use of individual antihistamines.

METHODS

A matched case-control study nested in a cohort of new users of antihistamines was conducted within the EU-funded ARITMO project. Data on 1997-2010 were retrieved from seven healthcare databases: AARHUS (Denmark), GEPARD (Germany), HSD and ERD (Italy), PHARMO and IPCI (Netherlands) and THIN (UK). Cases of VA were selected and up to 100 controls were matched to each case. The odds ratio (OR) of current use for individual antihistamines (AHs) was estimated using conditional logistic regression.

RESULTS

For agents largely used to prevent allergic symptoms, such as cetirizine, levocetirizine, loratadine, desloratadine and fexofenadine, we found no VA risk. A statistically significant, increased risk of VA was found only for current use of cyclizine in the pooled analysis (ORadj, 5.3; 3.6-7.6) and in THIN (ORadj, 5.3; 95% CI, 3.7-7.6), for dimetindene in GEPARD (ORadj, 3.9; 1.1-14.7) and for ebastine in GEPARD (ORadj, 3.3; 1.1-10.8) and PHARMO (ORadj, 4.6; 1.3-16.2).

CONCLUSIONS

The risk of VA associated with a few specific antihistamines could be ascribable to heterogeneity in pattern of use or in receptor binding profile.

Heart rate variability dynamics during controlled hypotension with nicardipine, remifentanil and dexmedetomidine

BACKGROUND

This study was done to investigate how nicardipine, remifentanil and dexmedetomidine affect the balance of the autonomic nervous system in patients receiving controlled hypotension under general anaesthesia by evaluating heart rate variability indices.

METHODS

Sixty-two patients were randomly allocated to either the nicardipine-sevoflurane (Group N, n = 21), remifentanil-sevoflurane (Group R, n = 21) or dexmedetomidine-sevoflurane (Group D, n = 20) group for controlled hypotension during orthognathic surgery. Electrocardiogram data acquisition was done after vital sign stabilization following anaesthesia induction (T1) and 30 min after controlled hypotension was induced (T2).

RESULTS

Total power and low frequency (LF) power was significantly decreased at T2 compared with T1 in all groups, while a decrease in high frequency (HF) power was only observed in Group N (P < 0.001). LF/HF ratios of Group R and D were significantly suppressed at T2 compared with T1 (P = 0.001 and P < 0.001, respectively), but was increased Group N (P = 0.009). The LF/HF ratio of Group N was significantly higher than Group R and D at T2 (P < 0.001 in both), with Group D showing a significantly lower LF/HF ratio compared with Group R (P < 0.001).

CONCLUSIONS

Remifentanil and dexmedetomidine did not have sympathetic nervous system-stimulating effects during controlled hypotension, while remifentanil seemed to be superior in preserving the overall balance in autonomic nervous system activity. Nicardipine was found to stimulate the sympathetic nervous system, which may be problematic in patients vulnerable to disturbances in the autonomic nervous system.

Integrated risk assessment and predictive value to humans of non-clinical repolarization assays

The potential for drugs to be associated with the life-threatening arrhythmia, Torsades de Pointes (TdeP), continues to be a topic of regulatory, academic and industrial concern. Despite being an imperfect biomarker, prolongation of the QT interval of the surface ECG is used to assess the risk of a drug being associated with TdeP such that a thorough examination of drug effects on the QT interval is required for all new chemical entities. Numerous studies have investigated the relationship between non-clinical findings and the risk of TdeP and QT prolongation in the general population. There are many literature references supporting the strong correlation between the clinical safety margin over human ether-a-go-go (hERG) inhibitory potency and the risk of drug-induced arrhythmia and sudden death. A quantitative analysis of the relationship between non-clinical studies and the outcome of a human Thorough QT study has also been reported. In the current manuscript, based on the outcome of the non-clinical assays the sensitivity and specificity of each assay and an integrated risk assessment for predicting the outcome of the human Thorough QT study has been conducted. The data suggest that for QT prolongation mediated through inhibition of the hERG current the non-clinical assays are highly predictive of drug effects on the QT interval. Based on the literature review and specific quantitative analysis reported above it is concluded that non-clinical assays predict the risk of compounds to prolong the QT interval and cause TdeP in humans if the mechanism is through inhibition of the hERG current.

The cardiovascular safety profile of renzapride, a novel treatment for irritable bowel syndrome

The cardiac safety of renzapride, a novel benzamide currently under clinical development for the treatment of irritable bowel syndrome, was investigated in a four-way randomized crossover electrocardiographic clinical study in healthy human subjects and also in an in vitro cardiac conductivity study in sheep isolated Purkinje fibres. The primary endpoint in the clinical study was prolongation of the individually corrected QT interval (QTci). No clinically or statistically significant prolongation of QTci after 4 or 20 mg renzapride compared with placebo was observed. The relative effects of renzapride and cisapride in the in vitro study showed that the cardiac action potential duration was unaltered by 0.2 and 2 microM renzapride, shortened by 20 microM renzapride, and prolonged by 1 microM cisapride. Cisparide was also a 1000-fold more potent inhibitor of human ether-a-go-go related gene (hERG) channels in HEK293 cells than renzapride. These studies indicate that therapeutic doses of renzapride are unlikely to prolong cardiac action potentials and, therefore, are also unlikely to cause cardiac arrhythmias in clinical use.