Highly sensitive analysis of tetrodotoxin based on free-label fluorescence aptamer sensing system

Tetrodotoxin (TTX) specifically can bind to its nucleic acid aptamer (TTX-aptamer) and cause the conformation of TTX-aptamer to be switched from the single-strand random coiling form to the compact neck ring structure. Based on the microenvironment difference of the fluorescence reporter, berberine in between the single-stranded coil oligonucleotides and the structure of the neck ring, a simple, rapid and sensitive label-free fluorescence aptamer sensing system for detection of TTX was developed. Various factors affecting the analysis of TTX were optimized, including the concentration of berberine, ion strength, pH, reaction time, the concentration of TTX-aptamer. Under the optimal experimental conditions, the fluorescence intensity of the sensing system and the concentration of TTX showed a good linear relationship in the range of 0.1 nM to 500 nM, with the detection limit of 0.074 nM. The standard recovery test result exhibited that the recoveries of TTX in serum samples were 96.54%-106.40%. The established method has the advantages of high specificity, good sensitivity, quickness and convenience, low cost, and can be used for the detection of TTX in serum samples.

Effect of ranolazine on glycaemic control in patients with type 2 diabetes treated with either glimepiride or metformin

AIM

To report the results of two phase III trials assessing the efficacy of ranolazine for glycaemic control in patients with type 2 diabetes on metformin or glimepiride background therapy.

METHODS

In two double-blind trials we randomized 431 and 442 patients with type 2 diabetes to ranolazine 1000 mg twice daily versus placebo added to either glimepiride (glimepiride add-on study) or metformin background therapy (metformin add-on study). Patients receiving ranolazine added to metformin had their metformin dose halved (with the addition of a metformin-matched placebo) relative to the placebo group to correct for a metformin-ranolazine pharmacokinetic interaction. The primary endpoint of the trials was the change from baseline in glycated haemoglobin (HbA1c) at week 24.

RESULTS

When added to glimepiride, ranolazine caused a 0.51% least squares mean [95% confidence interval (CI) 0.71, 0.32] decrease from baseline in HbA1c at 24 weeks relative to placebo and roughly doubled the proportion of patients achieving an HbA1c of <7% (27.1 vs 14.1%; p = 0.001). When added to metformin background therapy, there was no significant difference in the 24-week HbA1c change from baseline [placebo-corrected LS mean difference -0.11% (95% CI -0.31, 0.1)].

CONCLUSIONS

Compared with placebo, addition of ranolazine in patients with type 2 diabetes treated with glimepiride, but not metformin, significantly reduced HbA1c over 24 weeks. The decreased dose of metformin used in the metformin add-on study complicates the interpretation of this trial. Whether an effective regimen of ranolazine added to metformin for glycaemic control can be identified remains unclear.

[Flecainide poisoning]

Flecainide is an antiarrhythmic drug that blocks sodium channels during phase 0 of cardiac action potential, delaying conduction and reducing contractility. Intoxication by this drug is rare. Onset of effect, which is rapid, takes the form of hypotension and cardiac arrhythmias; mortality is high. No antidote is available and management is based on the few cases that have been reported. The metabolism of flecainide is affected by both kidney and liver failure, which lead to accumulation of the drug. Flecainide should not be used in patients with such failure unless the potential benefits clearly outweigh the risks. If flecainide is prescribed, diligent clinical, electrocardiographic, and hemodynamic vigilance is imperative and plasma levels of the drug should be monitored. We report a case of flecainide poisoning in which the drug was prescribed to treat atrial fibrillation in a woman with resolving sepsis with renal and hepatic complications.

Phase 1A safety assessment of intravenous amitriptyline

The antidepressant amitriptyline is used as an adjuvant in the treatment of chronic pain. Among its many actions, amitriptyline blocks Na+ channels and nerves in several animal and human models. As perioperative intravenous lidocaine has been suggested to decrease postoperative pain, amitriptyline, because of its longer half-life time, might be more useful than lidocaine. However, the use of intravenous amitriptyline is not approved by the US Food and Drug Administration. We therefore investigated the adverse effects of preoperative intravenous amitriptyline in a typical phase 1A trial. After obtaining written Food and Drug Administration and institutional review board approval, we obtained written consent for preoperative infusion of amitriptyline in an open-label, dose-escalating design (25, 50, and 100 mg, n=5 per group). Plasma levels of amitriptyline/nortriptyline were determined, and adverse effects were recorded in a predetermined symptom list. Infusion of 25 and 50 mg amitriptyline appears to be well tolerated; however, the study was terminated when 1 subject in the 100-mg group developed severe bradycardia. Intravenous infusion of amitriptyline (25 to 50 mg over 1 hour) did not create side effects beyond dry mouth and drowsiness, or dizziness, in 2 of our 10 otherwise healthy participants receiving the 25- to 50-mg dose. An appropriately powered future trial is necessary to determine a potential role of amitriptyline in decreasing postoperative pain.

PERSPECTIVE

Amitriptyline potently blocks the persistently open Na+ channels, which are known to be instrumental in various pain states. As this occurs at very low plasma concentrations, a single preoperative intravenous infusion of amitriptyline could provide long-lasting pain relief and decrease the incidence of chronic pain.

Effect of gender on the pharmacokinetics of eslicarbazepine acetate (BIA 2-093), a new voltage-gated sodium channel blocker

PURPOSE

To determine the effect of gender on the pharmacokinetics of eslicarbazepine acetate, a novel voltage-gated sodium channel blocker in the development for the treatment of epilepsy and bipolar disorder.

METHODS

Single-centre, open-label, parallel-group study in 12 female and 12 male healthy subjects. The study consisted of a single-dose (600 mg) period and a multiple-dose (600 mg, once-daily, for 8 days) period, separated by 4 days.

RESULTS

Eslicarbazepine acetate was rapidly and extensively metabolized to eslicarbazepine (S-licarbazepine), the main active metabolite. Following a single-dose, arithmetic mean eslicarbazepine maximum plasma concentrations (C(max)) and area under the plasma concentration-time curve over 24 h (AUC(0-24)) and from 0 to infinity (AUC(0-infinity)) were, respectively, 9.3 microg/ml, 128.5 microg h/ml and 171.9 microg h/ml in male subjects and 10.1 microg/ml, 150.1 microg h/ml and 205.0 microg h/ml in female subjects. At steady-state, C(max), AUC(0-24) and AUC(0-infinity) were 15.5 microg/ml, 207.8 microg h/ml and 295.8 microg h/ml in male subjects, and 16.8 microg/ml, 214.5 microg h/ml and 295.2 microg h/ml in female subjects. Steady-state plasma concentrations were attained at 4 to 5 days of administration in both groups. Eslicarbazepine C(max), AUC(0-24) and AUC(0-infinity) female:male geometric mean ratios (90%CI) were, respectively, 1.09 (0.94; 1.24), 1.16 (1.00; 1.33) and 1.17 (0.99; 1.38) following single-dose, and 1.10 (0.97; 1.25), 1.04 (0.92; 1.17) and 1.01 (0.88; 1.16) at steady-state.

CONCLUSION

At steady-state, the pharmacokinetic profile of eslicarbazepine acetate was not affected by gender.

Lidocaine-magnesium blood cardioplegia was equivalent to potassium blood cardioplegia in left ventricular function of canine heart

This study evaluated the effects of lidocaine-magnesium blood cardioplegia on left ventricular function compared with potassium blood cardioplegia. Crystalloid cardioplegia which contains lidocaine has been reported but blood cardioplegia is rare. Thirteen dogs received 60 min of global ischemia under hypothermic cardioplumonary bypass (30 degrees C). Potassium blood cardioplegia was administered every 20 min in group A (n=6), and lidocaine-magnesium blood cardioplegia in group B (n=7). We compared the ratio of Emax obtained during IVC occlusion at pre- and post-global ischemia (%Emax) and LVSW (%LVSV). Cardiac function was evaluated prior to CPB and 60 min after reperfusion. There was no difference in time required for cardiac arrest between the two groups (group A: 78+/-3 s, group B: 89+/-9 s). Percentage maximal elastance was significantly better in group B (group A: 63+/-3%, group B: 76+/-4%, P<0.05). Percentage tissue water content of the myocardium after CPB was significantly lower in group B (group A: 82.3+/-4%, group B: 75.5+/-2%, P<0.05). Lidocaine-magnesium blood cardioplegia was equivalent to potassium blood cardioplegia in systolic left ventricular function and reduced myocardial edema in canine heart.

Differentiation of the electrophysiological effects on the atrial myocardium between the pure Na channel blocker, pilsicainide, and flecainide

The purpose of this study was to identify the difference between the pure Na channel blocker, pilsicainide and Ic-antiarrhythmic drug, flecainide, on the atrial electrophysiological characteristics.

METHODS

The subjects consisted of 24 patients (48 +/- 12 years-old: P-group) in whom pilsicainide was administrated intravenously (1 mg/kg/10 min) and 31 patients (47 +/- 15 years-old: F-group) in whom flecainide was administrated intravenously (2 mg/kg/10 min). The atrial effective refractory period (ERP-A), intra-atrial conduction time (CT), max intra-atrial conduction delay (Max CD), repetitive atrial firing zone (RAFZ), fragmented atrial activity zone (FAZ) and intra-atrial conduction delay zone (CDZ) were measured before and after the drugs.

RESULTS

Pilsicainide and flecainide significantly prolonged the ERP-A (211 +/- 27 msec to 246 +/- 39 msec; p < 0.001, 217 +/- 25 msec to 244 +/- 33 msec; p < 0.001, respectively) and CT (121 +/- 33 msec to 149 +/- 43 msec; p < 0.001, 122 +/- 22 msec to 153 +/- 27 msec; p < 0.001, respectively) to the same degree. However, the Max CD was shortened by pilsicainide, but not by flecainide. The RAFZ, FAZ and CDZ decreased in the P-group (21 +/- 25 msec to 4 +/- 10 msec; p < 0.01, 24 +/- 24 msec to 14 +/- 18 msec; p < 0.05, 56 +/- 29 msec to 43 +/- 32 msec, p < 0.05, respectively), but not in the F-group.

CONCLUSIONS

The effects of atrial conduction delays may differ between pilsicainide and flecainide. Further examination will be needed to explain this mechanism.

Sample preparation and RPHPLC determination of diuretics in human body fluids

This article describes reverse phase high-performance liquid chromatography (RPHPLC) methods for determination of diuretics in different human body fluids (whole blood, plasma, serum or urine). Sample preparation procedures, including solid-phase extraction, liquid-liquid extraction, dilution, precipitation as well as automated RPHPLC procedures, are discussed in order to present the advantages and disadvantages of each type of sample preparation. Also, values of analytical recovery of each procedure used for sample preparation are summarized. The most important RPHPLC parameters (detection mode, stationary phase, mobile phase, sensitivity, etc.) are also summarized and discussed.

Pharmacokinetics of the new pyrimidine derivative NS-7, a novel Na+/Ca2+ channel blocker. 1st communication: plasma concentrations and excretions after a single intravenous 14C-NS-7 injection to rats, dogs and monkeys

Plasma concentration profiles and excretion were investigated after a single intravenous injection of 14C-NS-7 (4-(fluorophenyl)-2-methyl-6-(5-piperidinopentyloxy)pyrimidine hydrochloride, CAS 178429-67-9), a novel Na+/Ca2+ channel blocker, to rats, dogs and monkeys. Plasma protein binding of this drug was determined in vitro and in vivo. AUC0-infinity values for radioactivity and NS-7 after the intravenous administration of 14C-NS-7 to male rats increased with the dose, namely from 0.04 to 5 mg/kg (radioactivity) and from 0.2 to 5 mg/kg (NS-7), indicating the linearity of the drug's pharmacokinetics. Plasma concentrations of the unchanged drug after the intravenous injection of 0.2 mg/kg 14C-NS-7 decreased biexponentially, respective t1/2 beta values being 15.9 h in the male and 22.4 h in the female rats. The t1/2 beta values difference in the males and females might be due to sex differences in NS-7 metabolism. Urinary and fecal excretions of radioactivity within 168 h of administration were 33.0 and 61.4% of the dose in the male and 35.0 and 53.2% in the female rats. No radioactivity was detected in air exhaled from the males and females collected for 168 h after NS-7 administration. Within 24 h of administration, respective biliary excretions for the male and female rats were 26.1 and 11.9% of the dose. Of this excreted radioactivity, 34.9% was reabsorbed in the males. NS-7 plasma concentrations decreased biexponentially after intravenous administration of 0.2 mg/kg 14C-NS-7 to dogs and monkeys. The elimination half-life was 18 h for the dogs and 9.52 h for the monkeys. Urinary and fecal excretions of radioactivity within 168 h of administration were 24.2 and 70.0% of the dose for the dogs, and 63.3 and 24.8% for the monkeys. These species differences in excretion may be due to differences in urinary metabolite compositions. In vitro protein binding of NS-7 showed no marked species differences and was independent of the NS-7 concentration. Binding of 14C-NS-7 in the sera of rats, dogs, monkeys and humans was 90.7%, 73.5% 79.0% and 87.1%, respectively. Binding to human serum albumin, alpha 1-acid glycoprotein and lipoprotein was 56.2%, 45.4% and 79.5%, in the range of 4-40 ng/ml. In vivo binding in rat serum 5 min, 6 h and 24 h after the intravenous injection of 14C-NS-7(0.2 mg/kg) ranged from 89.6 to 90.6%.