连续口服不同剂量胺碘酮对健康受试者心率及心律的影响

目的:观察连续口服胺碘酮600~800 mg.d-1对健康受试者心率、心律的影响。方法:16名健康男性,每日600 mg或800 mg连续分次口服胺碘酮。服药至出现各种缓慢心律失常时停药。试验过程严密监测心电图(ECG)和24 h动态心电图(Holter)。结果:ECG:胺碘酮800 mg组服药1 d后白昼心率即有明显下降,停药3周恢复至药前水平;用药后ECG最早出现的改变为PR间期延长。Holter:服药3 d时胺碘酮800 mg.d-1组平均心率及24 h总心率数较用药前明显减低。停药1周两组平均心率及24 h总心率数与用药前比较差异无统计学意义。结论:胺碘酮致心律失常作用的最早表现为P-R间期延长,与剂量呈正相关,提示服用胺碘酮时应重视对PR间期的监测。     

The effect of heart rate on indices of myocardial contractility in the dog

1. Changes in heart rate were evoked by atrial pacing in anaesthetized dogs with no pretreatment and in dogs given reserpine or guanethidine for 72 h. The effect of alterations in heart rate were related to two indices of myocardial contractility: the maximal rate of change of left ventricular pressure (dp/dt), and an index which was independent of initial fibre length (dp/dt)/IIT, where IIT is integrated isometric tension. 2. An increase in heart rate in control dogs was accompanied by a rise in both dp/dt and (dp/dt)/IIT confirming that the Bowditch staircase does exist in the intact ventricle. The regression line relating heart rate to (dp/dt)/IIT was significantly steeper than that relating heart rate to dp/dt because the reduction in left ventricular preload at high heart rate tends to attenuate the rise in dp/dt. 3. Reserpine, but not guanethidine pretreatment was accompanied by either a slight decrease or no change in (dp/dt)/IIT during pacing. 4. Acute elevation of (dp/dt)/IIT by either calcium or isoprenaline infusion in reserpine pretreated dogs did not restore the Bowditch effect. 5. Acute depression of (dp/dt)/IIT by propranolol and pentobarbitone was accompanied by a greater rise in (dp/dt)/IIT with pacing in control dogs and a rise rather than a fall in reserpine-pretreated dogs.     

Thorough QT study of the effect of oral moxifloxacin on QTc interval in the fed and fasted state in healthy Japanese and Caucasian subjects

Aims

The aims of this study were three-fold and were to (i) investigate the effect of food (fasted and fed state) on the degree of QT prolongation caused by moxifloxacin under the rigorous conditions of a TQT study, (ii) differentiate the effects on QT_c that arise from changes in PK from those arising as a result of electrophysiological changes attributable to raised levels of C-peptide [11] offsetting in part the I_Kr blocking properties of moxifloxacin and (iii) characterize the QT_cF profile of oral moxifloxacin (400 mg) in healthy Japanese volunteers compared with Caucasian subjects.

Methods

The study population consisted of 32 healthy non-smoking, Caucasian (n = 13) and Japanese (n = 19), male and female subjects, aged between 20–45 years with a body mass index of between 18 to 25 kg m⁻². Female volunteers were required to use an effective contraceptive method or be abstinent. Subjects with ECGs which were deemed unsuitable for evaluation in a TQT study were excluded. ECGs were recorded in triplicate with subsequent blinded manual adjudication of the automated interval measurements. Electrocardiograms in the placebo arm were recorded twice in fasted and fed condition.

Results

The results demonstrated a substantial change in the typical moxifloxacin effect on the ECG. The effect on ΔΔQT_c in the fed state led to a significant delay and a modest reduction compared with the fasted state correcting both conditions with the corresponding placebo data. The largest QT_cF change from baseline in the fed state was observed at 4 h with a peak value of 11.6 ms (two-sided 90% CI 9.1, 14.1). In comparison, the largest QT_cF change observed in the fasted state was 14.4 ms (90% CI 11.9, 16.8) and occurred at 2.5 h post-dose. The PK of moxifloxacin were altered by food and this change was consistent with the observed QT_cF change. In the fed state plasma concentrations of moxifloxacin were considerably and consistently lower in comparison with the fasted state, and this applied to both ethnicities. The concentration–effect analysis revealed that there was no change in slope and confirmed that the difference in this analysis was caused by a change in the PK profile of moxifloxacin. Comparisons of the moxifloxacin effect in the fed state compared with fasted placebo also revealed a pharmacodynamic effect whereby a meal appears to antagonize the effects of moxifloxacin on the lengths of the QT_c interval.

Conclusions

Our findings demonstrate that the food effect by itself leads to a shortening of the QT_c interval offsetting in part the effects of a 400 mg single dose of oral moxifloxacin. The typical moxifloxacin PK profile is also altered by food prior to dosing reducing the C_max and delays the peak effects on QT_c up to several hours thereby reducing the overall magnitude of the effect and delaying the peak QT_c prolongation. The contribution of the two effects was clearly discernible. Given that moxifloxacin is sometimes given with food in TQT studies, consideration should be given to adequate baseline corrections and appropriate sampling time points. In this study the PK–PD relationship was similar for Japanese and Caucasian subjects in the fed and fasted conditions, thereby providing further evidence that the sensitivity to the QT_c prolonging effects of fluoroquinolones was likely to be independent of ethnicity. The small differences observed between the two subpopulations were not statistically significant. However, future studies should give consideration to formal ethnic comparisons as a secondary outcome parameter as very little is known about the relationship between ethnicity and drug effects on cardiac repolarization.     

The role of nuclear factors as “Find-Me”/alarmin signals and immunostimulation in defective efferocytosis and related disorders

Efferocytosis as an apoptotic cell (AC) clearance mechanism facilitates the removal of dangerous and damaged cells, an important process in regulating normal homeostasis. Failure to correctly execute apoptosis and efferocytosis is associated with atherosclerosis, as well as chronic inflammatory and autoimmune disorders such as systemic lupus erythematosus (SLE). Effective and timely efferocytosis involves various molecules that act as “Find-Me” signals or as alarmins to quickly allow identification by phagocytic cells. In recent years, most of these molecules have been investigated, but less attention has been paid to the nuclear molecules associated with efferocytosis of ACs and necrotic cells (NCs). These molecules have several functions including acting as alarmin signals for faster recognition of ACs, facilitating the cleanup of ACs and for maintaining self-tolerance. The same group of molecules is also implicated in several inflammatory and autoimmune diseases. Previous studies have shown that these molecules also serve as targets for pharmacological agents such as necrostatins, recombinant Fcnb, anti-histone, neutralizing antibodies, calbiochem, aminophylline, activated protein C, CD24IgG recombinant fission protein, and recombinant thrombomodulin. Thus, greater understanding of these molecules/pathways will enable developments in the treatment and/or prevention of various disorders, especially autoimmune diseases. Here, we review current knowledge about the mechanisms by which nucleic acids, histones, nucleosomes and monosodium urate microcrystals (MSU) can act as alarmins/“Find-Me” signals, how they might be stimulated in defective efferocytosis and their function and importance as biomarkers for prognosis and treatment of atherosclerosis, inflammatory disorders and autoimmune diseases.