[Analysis of the efficacy and influencing factors of sodium channel blockers in the treatment of focal epilepsy in infants under 6 months of age]

Objective: To analyze the efficacy and safety of the sodium channel blockers (SCB) antiseizure medication in the treatment of focal epilepsy in infants under 6 months of age. Methods: This was a case series study. Infants with focal epilepsy with onset within 6 months of age and treated with SCB attending the Department of Neurology of Beijing Children's Hospital from June 2016 to April 2022 were collected. The clinical data, auxiliary examinations, SCB application, efficacy, adverse reactions, and prognosis were analyzed retrospectively. Patients were grouped according to type of seizure and epileptic syndrome, age of onset and etiology. Chi square test and Fisher exact test were used to analyze the differences between groups statistically. Results: A total of 118 infants were enrolled, 65 males and 53 females, with an age of epilepsy onset of 56 (4, 114) days. Developmental and epileptic encephalopathy was diagnosed in 60 infants, 39 had self-limited neonatal and (or) infantile epilepsy, and 19 had non-syndromic focal epilepsy. Application of SCB: 106 used oxcarbazepine, 2 used lacosamide, 9 switched from oxcarbazepine to lacosamide or a combination of 2 SCB, and 1 used oxcarbazepine, lacosamide, and lamotrigine successively; oxcarbazepine was the first choice in 46 cases. The age at which SCB was applied was 103 (53, 144) days. The children were followed up for 6 months to 6 years. SCB was effective in 89 cases (75.4%), including 70 cases (59.3%) who achieved seizure freedom. The seizure-free rate was higher in the focal epilepsy only group than in the group with other seizure types (64.4% (65/101) vs. 4/17, χ²=9.99, P<0.05). The responder and seizure-free rates were all higher in the group with the onset age of >3-6 months than the group >1-3 months (84.4% (38/45) vs. 62.5% (20/32), 73.3% (33/45) vs. 46.9% (15/32), χ²=4.85 and 5.58, both P<0.05). With the exception of variants in the PRRT2 gene, those with variants in sodium or potassium channels had higher responder and seizure-free rates than those with variants in other genes(86.2% (25/29) vs. 45.5% (10/22), 62.1% (18/29) vs. 22.7% (5/22), χ²=9.65 and 7.82,both P<0.05). The most common adverse event was transient hyponatremia, which happened in 66 cases (55.9%). There were 9 cases of rash, which subsided in 6 cases after discontinuing oxcarbazepine and switching to lacosamide, and 7 cases of electrocardiogram abnormalities, which improved after withdrawing oxcarbazepine and changing to lacosamide in 1 case. Conclusion: SCB are effective and tolerable in the treatment of focal epilepsy in infants under 6 months of age, with better efficacy in patients with genetic variants of the sodium or potassium channel, focal seizures only, and seizure onset >3-6 months of age.

Ranolazine in the prevention and treatment of atrial fibrillation: A protocol for meta-analysis

BACKGROUND

Atrial fibrillation (AF) is the most common clinical arrhythmia and a major cause of morbidity and mortality in clinical practice. This study aims to determine the ranolazine for prevention and treatment of atrial fibrillation.

METHOD

This study adheres to the Preferred Reporting Items for Systematic Reviews and Meta-analysis for Protocols. Chinese electronic Database (CBM, Wanfang, and CNKI) and international electronic databases (PubMed, Embase, Cochrane Library, and Web of Science) will be searched for all relevant published articles. We will apply no language or the year of publication restrictions. Study selection, data collection, and assessment of study bias will be conducted independently by a pair of independent reviewers. The Cochrane risk of bias (ROB) tool will be used for the risk of bias assessment. The quality of evidence will be evaluated by Grading of Recommendations Assessment Development and Evaluation (GRADE) system. The statistical analysis of this meta-analysis will be calculated by Review manager version 5.3.

RESULTS

The results of this study will be published in a peer-reviewed journal.

CONCLUSION

This review will evaluate the value of ranolazine interventions for patients with AF, and provide meaningful conclusions or high-level evidence for clinical practice and further research.

TRIAL REGISTRATION

This study protocol was registered in open Science framework (OSF), (Registration DOI: 10.17605/OSF.IO/T6W9Q).

Therapeutic Monitoring of Lacosamide in Japanese Patients With Epilepsy: Clinical Response, Tolerability, and Optimal Therapeutic Range

BACKGROUND

Lacosamide is a novel anticonvulsant that acts by enhancing sodium channel slow inactivation. The aims of this study were to evaluate the influence of concomitant antiepileptic drugs (AEDs) on serum lacosamide concentration and explore the relationship between lacosamide serum concentration and both clinical response and adverse effects.

METHODS

The authors analyzed 649 serum samples from 426 Japanese patients with epilepsy. The concentration-to-dose (CD) ratio of lacosamide was compared among patients on various AED regimens. Clinical information about seizure frequency and adverse events was obtained from clinical records.

RESULTS

In patients who did not receive enzyme-inducing AEDs, the CD ratio (mean ± SD) of lacosamide was 1.84 ± 0.68. By contrast, the CD ratio in patients who received phenytoin, carbamazepine, and phenobarbital was 1.42 ± 0.66 (22.8% lower), 1.46 ± 0.40 (20.7% lower), and 1.36 ± 0.38 (26.1% lower), respectively. Seventy-four patients (17.3%) achieved >50% seizure reduction. The median lacosamide concentration in patients who received and did not receive a sodium channel blocker was 6.6 mcg/mL (26.4 μmol/L) and 8.4 mcg/mL (33.6 μmol/L), respectively. Adverse events, including dizziness, somnolence, diplopia, and anorexia, were reported by 70 patients (16.4%). The incidence rate in patients treated with sodium channel blockers was significantly higher than that in patients not treated with these drugs (21.1% vs. 10.3%; P < 0.005), and the median lacosamide concentration in these patient groups was 5.1 (20.4 μmol/L) and 7.5 mcg/mL (30 μmol/L), respectively.

CONCLUSIONS

Therapeutic drug monitoring of lacosamide is clinically useful because it allows physicians to estimate the extent of drug interactions and adjust the dose in individual AED regimens.

Sodium channels and pain: from toxins to therapies

Voltage-gated sodium channels (NaV channels) are essential for the initiation and propagation of action potentials that critically influence our ability to respond to a diverse range of stimuli. Physiological and pharmacological studies have linked abnormal function of NaV channels to many human disorders, including chronic neuropathic pain. These findings, along with the description of the functional properties and expression pattern of NaV channel subtypes, are helping to uncover subtype specific roles in acute and chronic pain and revealing potential opportunities to target these with selective inhibitors. High-throughput screens and automated electrophysiology platforms have identified natural toxins as a promising group of molecules for the development of target-specific analgesics. In this review, the role of toxins in defining the contribution of NaV channels in acute and chronic pain states and their potential to be used as analgesic therapies are discussed.

LINKED ARTICLES

This article is part of a themed section on Recent Advances in Targeting Ion Channels to Treat Chronic Pain. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.12/issuetoc.

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.

Differential inhibition of cardiac and neuronal Na(+) channels by the selective serotonin-norepinephrine reuptake inhibitors duloxetine and venlafaxine

Duloxetine and venlafaxine are selective serotonin-norepinephrine-reuptake-inhibitors used as antidepressants and co-analgesics. While venlafaxine rather than duloxetine induce cardiovascular side-effects, neither of the substances are regarded cardiotoxic. Inhibition of cardiac Na(+)-channels can be associated with cardiotoxicity, and duloxetine was demonstrated to block neuronal Na(+)-channels. The aim of this study was to investigate if the non-life threatening cardiotoxicities of duloxetine and venlafaxine correlate with a weak inhibition of cardiac Na(+)-channels. Effects of duloxetine, venlafaxine and amitriptyline were examined on endogenous Na(+)-channels in neuroblastoma ND7/23 cells and on the α-subunits Nav1.5, Nav1.7 and Nav1.8 with whole-cell patch clamp recordings. Tonic block of the cardiac Na(+)-channel Nav1.5 and rat-cardiomyocytes (CM) revealed a higher potency for duloxetine (Nav 1.5 IC50 14±1µM, CM IC50 27±3µM) as compared to venlafaxine (Nav 1.5 IC50 671±26µM, CM IC50 452±34µM). Duloxetine was as potent as the cardiotoxic antidepressant amitriptyline (IC50 13±1µM). While venlafaxine almost failed to induce use-dependent block on Nav1.5 and cardiomyocytes, low concentrations of duloxetine (1, 10µM) induced prominent use-dependent block similar to amitriptyline. Duloxetine, but not venlafaxine stabilized fast and slow inactivation and delayed recovery from inactivation. Duloxetine induced an unselective inhibition of neuronal Na(+)-channels (IC50 ND7/23 23±1µM, Nav1.7 19±2µM, Nav1.8 29±2). Duloxetine, but not venlafaxine inhibits cardiac Na(+)-channels with a potency similar to amitriptyline. These data indicate that an inhibition of Na(+)-channels does not predict a clinically relevant cardiotoxicity.

[Clinical experience with lacosamide in Galicia: the GALACO study]

INTRODUCTION

Lacosamide is a sodium channel blocker antiepileptic drug authorized as an adjunctive therapy for focal seizures in adolescents and adults.

AIM

To analyze the efficacy and safety of lacosamide in Galicia according to its use in daily clinical practice.

PATIENTS AND METHODS

Retrospective observational study in patients who started treatment with lacosamide between January 2014 and June 2013 in 10 hospitals in Galicia, Spain. Its efficacy and safety at 3, 6 and 12 months after starting lacosamide was assessed.

RESULTS

We included 184 patients with a mean age of 44.2 ± 17.4 years old; 56.5% (n = 104) were male; 173 patients constituted the efficacy population. Mean duration of epilepsy was 18.8 ± 15.5 years. Seizure frequency was 2.5 ± 1.6 episodes/month. After 12 months, 68.2% of patients (n = 118) had >= 50% improvement (responders) and among them, 54 (45.8% of responder patients) were seizure free. Twenty-three percent (n = 43) suffered from adverse events after 12 months, being dizziness (10.3%) and instability (3.3%) the most frequently reported. After the 12 month visit, 87.5% of patients (n = 161) continued treatment with lacosamide.

CONCLUSIONS

Lacosamide provides a very good efficacy and safety profile for patients with focal refractory epilepsy. High percentage of responders may be related to a less refractory population compared to other daily clinical practice studies. It constitutes an attractive therapeutic option for the treatment of focal epilepsies.

Sodium channel blockers for neuroprotection in multiple sclerosis

BACKGROUND

Multiple sclerosis (MS) is an autoimmune, inflammatory, demyelinating disease of the central nervous system (CNS), which can occur in many parts of the CNS and result in a wide range of symptoms including sensory impairment, fatigue, walking or balance problems, visual impairment, vertigo and cognitive disabilities. At present, the most commonly used MS treatments are immunomodulating agents, but they have little effect on the disability. Experimental studies show that sodium (Na(+)) accumulation leads to intracellular calcium (Ca(2+)) release, and the increased calcium levels can activate nitric oxide synthase and harmful proteases and lipases. These factors contribute to axonal injury in people with MS. If partial blockade of voltage-gated sodium channels could result in neuroprotection, this would be of benefit for preventing disability progression in these people. Neuroprotection is emerging as a potentially important strategy for preventing disability progression in people with MS.

OBJECTIVES

To assess the efficacy and safety of sodium channel blockers for neuroprotection in people with MS to prevent the occurrence of disability and alleviate the burden of the disease.

SEARCH METHODS

We searched the Cochrane Multiple Sclerosis and Rare Diseases of the Central Nervous System Group Specialised Register (27 August 2015) which, among other sources, contains references from the Cochrane Central Register of Controlled Trials (CENTRAL) (Cochrane Library 2015, Issue (8), MEDLINE (1966 to August 2015), EMBASE (1974 to August 2015), Cumulative Index to Nursing and Allied Health Literature (CINAHL) (1981 to August 2015), Latin American and Caribbean Health Science Information Database (LILACS) (1982 to August 2015), ClinicalTrials.gov (http://clinicaltrials.gov) and the World Health Organization (WHO) International Clinical Trials Registry Portal (ICTRP) search portal (http://apps.who.int/trialsearch). In addition, we searched four Chinese databases, ongoing trials registers and relevant reference lists.

SELECTION CRITERIA

Randomised controlled trials (RCTs) that examined sodium channel blockers used alone or as an add-on to any approved treatments for MS.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials, assessed trial quality and extracted the data.

MAIN RESULTS

Only one study evaluating lamotrigine in secondary progressive MS was eligible. One hundred and twenty people were included, 61 randomly assigned to lamotrigine treatment and 59 to placebo treatment. The average age of participants in the two groups was 51.9 years and 50.1 years, respectively. The proportion of male participants was 27.5%. The period of follow-up was 2 years. No data were found on disability progression and people who experienced relapses. No significant differences were found for serious adverse events between the two groups. Treatment with lamotrigine was associated with more rashes (20% vs 5%, P value 0.03) and transient, dose-related deterioration of mobility (66% vs 34%, P value 0.001) than placebo. Furthermore, no significant difference between the two groups was found in the magnetic resonance imaging (MRI) measurements of cerebral atrophy, Expanded Disability Status Score changes, Multiple Sclerosis Functional Composite score changes. This study was judged to be at high risk of bias. This review will be updated when the three ongoing studies we identified are completed.

AUTHORS' CONCLUSIONS

The quality of evidence was judged to be very low due to the low number of available studies and included participants. There is a lack of evidence to address the review question on the efficacy of sodium channel blockers for people with MS. Assessment of the three ongoing trials might change this conclusion. Further high-quality large scale studies are needed.

Editorial note

No update planned, no new version forthcoming.

Effects of ranolazine on left ventricular diastolic and systolic function in patients with chronic coronary disease and stable angina

INTRODUCTION

The present study examined the effect of ranolazine, which acts via the mechanism of selective inhibition of late INa+, on parameters of left ventricular systolic and diastolic function in patients suffering from angiographically confirmed chronic coronary artery disease, presenting with chronic stable angina.

METHODS

We studied 40 patients (age 67 ± 9 years; 30 men, 10 women) with chronic coronary artery disease who reported angina symptoms on optimal medication and who were not suitable for invasive treatment. Patients were randomized to the ranolazine group (group A, 20 patients taking oral ranolazine 500 mg bid for 3 months) and the control group (group B, 20 patients who did not receive the drug). Left ventricular systolic and diastolic function was assessed echocardiographically at baseline and after the end of the three-month treatment period. Left ventricular ejection fraction by the modified Simpson's method, E and A left ventricular filling velocities, E/A ratio, deceleration time (DT) of E, isovolumic relaxation time (IVRT), E and A waves, and the E/E ratio were measured using 2-dimensional echocardiography, Doppler and tissue Doppler imaging (TDI).

RESULTS

Group A patients demonstrated a clear improvement of their initial angina symptoms. There were no adverse effects from ranolazine requiring withdrawal from the study. There was no statistically significant change in left ventricular systolic function in either group. A statistically significant change was seen in indexes of diastolic function measured using both conventional Doppler and TDI in Group A patients compared with Group B patients after three months' ranolazine treatment period. The changes in left ventricular diastolic function indexes in Group A patients were as follows: E 0.58 ± 0.11 vs. 0.76 ± 0.12 m/s, p<0.001; A 0.71 ± 0.22 vs. 0.83 ± 0.19 m/s, p<0.001; E/A 0.81 ± 0.14 vs. 0.97 ± 0.17, p<0.005; 5.4 ± 0.7 vs. 6.8 ± 0.9 cm/s, p<0.005; 7.2 ± 0.8 vs. 8.3 ± 1.1 cm/s, p<0.005; E/ 10.7 ± 1.1 vs. 11.1 ± 0.8, p=ns; DT 251 ± 14 vs. 226 ± 17 ms, p<0.004; IVRT 95 ± 11 vs. 74 ± 9 ms, p<0.001. Systolic function did not change: EF 46.3 ± 3.4 vs. 46.7 ± 2.7%, p: ns.

CONCLUSIONS

The use of ranolazine in patients suffering from chronic coronary artery disease has a favorable impact on diastolic function parameters. Accordingly, a clinical benefit could be observed due to an improvement in patients' symptoms.

[CONVULSIVE EFFECTS OF ANTIEPILEPTIC AGENTS]

Antiepileptic drugs can provoke and worsen seizures, what is called paradoxical effect. Paradoxical seizure worsening can occur as a nonspecific manifestation of drug intoxication in number of antiepileptic drugs. The other type is a specific type, when antiepileptic drugs with pure GABAergic and sodium channel blocker mechanism of action provoke myoclonic, absence and atonic seizures in specific epilepsy syndromes, mainly in idiopathic generalized epilepsies. Antiepileptic drug-induced exacerbation of seizures is a common, often unrecognized clinical problem, which can be avoided by a careful syndromic diagnosis and by using broad spectrum antiepileptic drugs.

[Effect of lacosamide on the quality of life of patients with epilepsy]

INTRODUCTION

Epilepsy causes psychiatric disorders in 20-40% of patients impacting negatively on their quality of life. Lacosamide is a new antiepileptic as adjunctive therapy in partial seizures with or without generalization.

AIM

We conducted a study to assess the impact of lacosamide as to the quality of life of epileptic patients. We used the HAD scale for anxiety and depression and QOLIE-10 scale for quality of life. We evaluated the efficacy and tolerability.

PATIENTS AND METHODS

We collected prospectively poorly controlled epileptic patients are and added lacosamide treatment. Baseline visit, at 3 and 6 months were performed. The questionnaires are completed and the epilepsy information has been collected.

RESULTS

31 patients, age 45.5 ± 17.2 years, 64.5% males are included. Number of previous monthly crisis 1.6 ± 1.8. HAD anxiety scale shows a significant improvement at 3 and 6 months. HAD scale for depression reflects a significant improvement in quality parameters. QOLIE-10 shows significant improvement for the group with low quality of life after 3 and 6 months. After 6 months 61.3% of patients have a seizure reduction equal or more than 50% and 54.8% are seizure free. Dizziness is the most common side effect (22.8%). 74.2% continued treatment.

CONCLUSIONS

Lacosamide may improve anxiety, depression and quality of life of epileptic patients regardless of seizure control. Response to treatment, adherence and side effects are similar to previous studies.

Update on ranolazine in the management of angina

Mortality rates attributable to coronary heart disease have declined in recent years, possibly related to changes in clinical presentation patterns and use of proven secondary prevention strategies. Chronic stable angina (CSA) remains prevalent, and the goal of treatment is control of symptoms and reduction in cardiovascular events. Ranolazine is a selective inhibitor of the late sodium current in myocytes with anti-ischemic and metabolic properties. It was approved by the US Food and Drug Administration in 2006 for use in patients with CSA. Multiple, randomized, placebo-controlled trials have shown that ranolazine improves functional capacity and decreases anginal episodes in CSA patients, despite a lack of a significant hemodynamic effect. Ranolazine did not improve cardiovascular mortality or affect incidence of myocardial infarction in the MERLIN (Metabolic Efficiency with Ranolazine for Less Ischemia in Non-ST-Elevation Acute Coronary Syndrome)-TIMI (Thrombolysis In Myocardial Infarction) 36 trial, but significantly decreased the incidence of recurrent angina. More recently, ranolazine has been shown to have beneficial and potent antiarrhythmic effects, both on supraventricular and ventricular tachyarrhythmias, largely due to its inhibition of the late sodium current. Randomized controlled trials testing these effects are underway. Lastly, ranolazine appears to be cost-effective due to its ability to decrease angina-related hospitalizations and improve quality of life.

Neurological adverse events of new generation sodium blocker antiepileptic drugs. Meta-analysis of randomized, double-blinded studies with eslicarbazepine acetate, lacosamide and oxcarbazepine

PURPOSE

Analysis of overall tolerability and neurological adverse effects (AEs) of eslicarbazepine acetate (ESL), lacosamide (LCM) and oxcarbazepine (OXC) from double-blind, placebo-controlled trials. Indirect comparisons of patients withdrawing because of AEs, and the incidence of some vestibulocerebellar AEs between these three antiepileptic dugs (AEDs).

METHODS

We searched MEDLINE for all randomized, double-blind, placebo-controlled trials investigating therapeutic effects of fixed oral doses of ESL, LCM and OXC in patients with drug resistant epilepsy. Withdrawal rate due to AEs, percentages of patients with serious AEs, and the proportion of patients experiencing any neurological AE, nausea and vomiting were assessed for their association with the experimental drug. Analyses were performed between recommended daily doses of each AED according to the approved summary of product characteristics (SPC). Risk differences were used to evaluate the association of any AE [99% confidence intervals (CIs)] or study withdrawals because of AEs (95% CIs) with the experimental drug. Indirect comparisons between withdrawal rate and AEs dizziness, coordination abnormal/ataxia and diplopia were estimated according to network meta-analysis (Net-MA).

RESULTS

Eight randomized, placebo-controlled, double-blind trials (4 with ESL, 3 with LCM, and 1 with OXC) were included in our analysis. At high doses (OXC 1200mg, ESL 1200mg and LCM 400mg) there was an increased risk of AE-related study withdrawals compared to placebo for all drugs. Several AEs were associated with the experimental drug. Both number and frequency of AEs were dose-related. At high recommended doses, patients treated with OXC withdrew from the experimental treatment significantly more frequently than patients treated with ESL and LCM. Furthermore, the AEs coordination abnormal/ataxia and diplopia were significantly more frequently observed in patients treated with OXC compared to patients treated with LCM and ESL.

CONCLUSIONS

The overall tolerability of AEDs and the incidence of several neurological AEs were clearly dose-dependent. Indirect comparisons between these AEDs, taking into account dose-effect, showed that OXC may be associated with more frequent neurological AEs than LCM and ESL.

Selective SGLT2 inhibition by tofogliflozin reduces renal glucose reabsorption under hyperglycemic but not under hypo- or euglycemic conditions in rats

To understand the risk of hypoglycemia associated with urinary glucose excretion (UGE) induced by sodium-glucose cotransporter (SGLT) inhibitors, it is necessary to know the relationship between the ratio of contribution of SGLT2 vs. SGLT1 to renal glucose reabsorption (RGR) and the glycemic levels in vivo. To examine the contributions of SGLT2 and SGLT1 in normal rats, we compared the RGR inhibition by tofogliflozin, a highly specific SGLT2 inhibitor, and phlorizin, an SGLT1 and SGLT2 (SGLT1/2) inhibitor, at plasma concentrations sufficient to completely inhibit rat SGLT2 (rSGLT2) while inhibiting rSGLT1 to different degrees. Under hyperglycemic conditions by glucose titration, tofogliflozin and phlorizin achieved ≥50% inhibition of RGR. Under hypoglycemic conditions by hyperinsulinemic clamp, RGR was reduced by 20-50% with phlorizin and by 1-5% with tofogliflozin, suggesting the smaller contribution of rSGLT2 to RGR under hypoglycemic conditions than under hyperglycemic conditions. Next, to evaluate the hypoglycemic potentials of SGLT1/2 inhibition, we measured the plasma glucose (PG) and endogenous glucose production (EGP) simultaneously after UGE induction by SGLT inhibitors. Tofogliflozin (400 ng/ml) induced UGE of about 2 mg·kg⁻¹·min⁻¹ and increased EGP by 1-2 mg·kg⁻¹·min⁻¹, resulting in PG in the normal range. Phlorizin (1,333 ng/ml) induced UGE of about 6 mg·kg⁻¹·min⁻¹ and increased EGP by about 4 mg·kg⁻¹·min⁻¹; this was more than with tofogliflozin, but the minimum PG was lower. These results suggest that the contribution of SGLT1 to RGR is greater under lower glycemic conditions than under hyperglycemic conditions and that SGLT2-selective inhibitors pose a lower risk of hypoglycemia than SGLT1/2 inhibitors.

The 'overly-sensitive' heart: sodium channel block and QRS interval prolongation

Cardiac safety remains of paramount importance in the development of successful clinical drug candidates. Great progress has been made recently in understanding liabilities associated with delayed ventricular repolarization (manifest as QT prolongation) and in predicting (thus avoiding) drugs that delay repolarization based on application of strategic preclinical assays. Following the advances made in clinical electrophysiological monitoring and conduct of thorough QT studies, focus is now shifting towards monitoring of additional drug-induced effects, particularly on ventricular conduction (measured as changes in the QRS interval on the ECG) as part of evolving clinical thorough ECG studies. In this issue of the British Journal of Pharmacology, a study by Harmer et al. proposes provisional safety margins for QRS prolongation in man based on retrospective clinical data and a single in vitro approach to assess potency of block of cardiac sodium current (hNav1.5), the ionic current responsible for ventricular conduction (observed as QRS prolongation). The present commentary places their study in context with evolving preclinical cardiac electrophysiological safety assessments, along with discussions focused on ensuring the proper 'translation' of preclinical findings with potential clinical concerns. Given the extant limitations and uncertainties of presently available data, as well as our limited understanding of the pro-arrhythmic potential associated with these changes, due caution should be applied when considering the proposed in vitro-based margins for drug-induced QRS prolongation measured clinically. Additional validation with multiple preclinical models and more rigorous clinical safety studies will be necessary to substantiate these recommended margins.

LINKED ARTICLE

This article is a commentary on Harmer et al., pp. 260-273 of this issue. To view this paper visit http://dx.doi.org/10.1111/j.1476-5381.2011.01415.x.

Simulation of multiple ion channel block provides improved early prediction of compounds' clinical torsadogenic risk

AIMS

The level of inhibition of the human Ether-à-go-go-related gene (hERG) channel is one of the earliest preclinical markers used to predict the risk of a compound causing Torsade-de-Pointes (TdP) arrhythmias. While avoiding the use of drugs with maximum therapeutic concentrations within 30-fold of their hERG inhibitory concentration 50% (IC(50)) values has been suggested, there are drugs that are exceptions to this rule: hERG inhibitors that do not cause TdP, and drugs that can cause TdP but are not strong hERG inhibitors. In this study, we investigate whether a simulated evaluation of multi-channel effects could be used to improve this early prediction of TdP risk.

METHODS AND RESULTS

We collected multiple ion channel data (hERG, Na, L-type Ca) on 31 drugs associated with varied risks of TdP. To integrate the information on multi-channel block, we have performed simulations with a variety of mathematical models of cardiac cells (for rabbit, dog, and human ventricular myocyte models). Drug action is modelled using IC(50) values, and therapeutic drug concentrations to calculate the proportion of blocked channels and the channel conductances are modified accordingly. Various pacing protocols are simulated, and classification analysis is performed to evaluate the predictive power of the models for TdP risk. We find that simulation of action potential duration prolongation, at therapeutic concentrations, provides improved prediction of the TdP risk associated with a compound, above that provided by existing markers.

CONCLUSION

The suggested calculations improve the reliability of early cardiac safety assessments, beyond those based solely on a hERG block effect.

[Class I antiarrhythmic drugs: mechanisms, contraindications, and current indications]

Class I antiarrhythmic drugs are sodium channel inhibitors that act by slowing myocardial conduction and, thus, interrupting or preventing reentrant arrhythmia. Due to proarrhythmic effects and the risk of ventricular tachyarrhythmia, class I antiarrhythmics should not be administered in patients with structural heart disease. Nevertheless, there remains a broad spectrum of arrhythmias--among the most common being atrial fibrillation--that can successfully be treated with class I antiarrhythmic drugs. This review gives an overview on the classification, antiarrhythmic mechanisms, indications, side effects, and application modes of class I antiarrhythmic drugs.

Vernakalant, a mixed sodium and potassium ion channel antagonist that blocks K(v)1.5 channels, for the potential treatment of atrial fibrillation

Despite being the most common arrhythmia currently treated by cardiologists, safe and effective treatments for atrial fibrillation (AF) remain elusive. To address this issue, Astellas Pharma Inc, Merck & Co Inc and Cardiome Pharma Corp are developing vernakalant (RSD-1235), a drug which dose-dependently inhibits sodium channels and several potassium repolarizing currents. Of particular note, vernakalant inhibits I(Kur) (K(v)1.5), a current that is more predominant in atrial than in ventricular tissue. Consistent with this observation, vernakalant produced increases in atrial refractory period with minimal actions on QTc interval or ventricular refractory period in both humans and animals. Intravenous vernakalant terminated recent-onset AF in several animal models, and also in patients with short-duration AF or AF following cardiac surgery enrolled in phase II and III clinical trials. Vernakalant was well tolerated and adverse reactions were transient and mild. Thus, vernakalant holds considerable promise for the treatment of recent-onset AF; however, given its relatively short half-life, continuous dosing may be required in order to maintain sinus rhythm following conversion from AF. The efficacy and safety of vernakalant for the long-term management of AF remains to be determined. Phase III clinical trials with intravenous vernakalant are ongoing, and phase II clinical trials are also being conducted with an oral formulation intended for chronic use.

Ranolazine: a new approach to treating an old problem

Chronic angina pectoris affects millions of patients every year. During the past 2 decades, advances in medical therapy have led to substantial reductions in the symptoms of angina. Nonetheless, many patients continue to experience persistent angina that causes debilitating symptoms and lifestyle changes. Moreover, many current therapeutic agents cause side effects that can induce substantial morbidity on their own. In major clinical trials, the drug ranolazine has been shown to bring symptomatic relief to large numbers of patients who have chronic angina. Herein, we review the physiology of the sodium channel; the pharmacology of ranolazine; clinical trials that support use of the drug; recent evidence about ranolazine's therapeutic effect on diastolic heart failure, glycemic control, and atrial fibrillation and other arrhythmias; officially approved clinical indications; and avenues of future study.

Lidocaine, tetrodotoxin and their effect on consolidation of spatial memory

This study was aimed at comparing the effect of unilateral hippocampal inactivation with tetrodotoxin (TTX) and lidocaine on spatial memory consolidation. Both drugs block voltage-dependent sodium channels. However, TTX and lidocaine differ in the duration of their effects, with maximum TTX effect between 30 min and 120 min, washing out in 24 hours. Lidocaine maximum effect occurs 20-30 minutes after administration. Our experimental subjects, twenty-four 3-month-old Wistar rats, were unilaterally implanted with stainless-steel cannulae aimed at the right dorsal hippocampus. Animals received four daily trials for 5 consecutive days. Control injections of 1 microl saline, or inactivating injections of 5 ng of TTX in 1 microl saline or lidocaine (2%) in 1 microl were made through a guide cannula 1 minute after the last trial from day 1 to day 4. Results showed that the groups that received TTX or lidocaine did not differ but were impaired regarding controls, suggesting that short-term consolidation processes can account for the memory impairment observed here.

[Nonlinear nature of the antiarrhythmic effects of lidocain]

For the first time experimental evidence for the nonlinear dependence of the antiarrhythmic effect of the Na-channel blocker on its concentration was obtained. The experiments were carried out with the use of a preparation of the mammalian heart wall. As a blockator, lidocain was used. It was found that the dependence of the antiarrhythmic effect of lidocain on its concentration has a well-pronounced nonlinear nature: while its therapeutic concentrations make ventricular arrhythmias more monomorphic, low concentrations of lidocain increase the probability for the arrhythmias to appear more polymorphic.

The cardiac persistent sodium current: an appealing therapeutic target?

The sodium current in the heart is not a single current with a mono-exponential decay but rather a mixture of currents with different kinetics. It is not clear whether these arise from distinct populations of channels, or from modulation of a single population. A very slowly inactivating component, [(INa(P))] I(Na(P)) is usually about 1% of the size of the peak transient current [I(Na(T))], but is enhanced by hypoxia. It contributes to Na(+) loading and cellular damage in ischaemia and re-perfusion, and perhaps to ischaemic arrhythmias. Class I antiarrhythmic agents such as flecainide, lidocaine and mexiletine generally block I(NA(P)) more potently than block of I(Na(T)) and have been used clinically to treat LQT3 syndrome, which arises because mutations in SCN5A produce defective inactivation of the cardiac sodium channel. The same approach may be useful in some pathological situations, such as ischaemic arrhythmias or diastolic dysfunction, and newer agents are being developed with this goal. For example, ranolazine blocks I(Na(P)) about 10 times more potently than I(Na(T)) and has shown promise in the treatment of angina. Alternatively, the combination of I(Na(P)) block with K(+) channel block may provide protection from the induction of Torsades de Pointe when these agents are used to treat atrial arrhythmias (eg Vernakalant). In all of these scenarios, an understanding of the role of I(Na(P)) in cardiac pathophysiology, the mechanisms by which it may affect cardiac electrophysiology and the potential side effects of blocking I(Na(P)) in the heart and elsewhere will become increasingly important.

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.

Incidence and Initial Characteristics of Pilsicainide-Induced Ventricular Arrhythmias in Patients With Brugada Syndrome

BACKGROUND

In patients with Brugada syndrome, class I antiarrhythmic drugs can trigger ventricular arrhythmias (VA). The incidence and initial characteristics of VA that developed after pilsicainide was examined in 28 patients with Brugada-type electrocardiographic (ECG) abnormalities and with a positive response in the pilsicainide test. The clinical outcome was also compared between patients with and without pilsicainide-induced VA.

METHODS AND RESULTS

In all patients, pilsicainide increased ST segment elevation and accentuated type 1 ECG changes. Ventricular tachycardia (VT) developed in 3 patients and premature ventricular complexes (PVC) in 2 other patients. These 5 patients (group I) had higher ST segment elevation in lead V2 on the ECG at baseline and after pilsicainide and showed a longer QTc interval after pilsicainide than the other 23 patients (group II). However, there was no difference between the 2 groups regarding incidence of prior cardiac events, results of signal-averaged ECG, HV interval, inducibility of ventricular fibrillation by programmed electrical stimulation, or QRS duration. In 1 patient, PVC originated from 3 sites, 2 of which triggered polymorphic VT. The right ventricular (RV) outflow tract was the origin of 2 types of PVC, and other RV sites of 5 other types. During a 45 +/- 37 months follow-up, polymorphic VT recurred in 2 patients in group II.

CONCLUSIONS

Pilsicainide induced VA in some patients with Brugada syndrome, but this result may not be used as a parameter of the risk stratification of Brugada syndrome. Multiple PVC induced by pilsicainide and triggering polymorphic VT originated from several RV sites is an important factor when considering patients for treatment with catheter ablation.

Reversible inactivation of amygdala and cerebellum but not perirhinal cortex impairs reactivated fear memories

The cerebellum, amygdala and perirhinal cortex are involved in fear learning but the different roles that these three structures play in aversive learning are not well defined. Here we show that in adult rats amygdala or cerebellar vermis blockade causes amnesia when performed immediately, but not 1 h, after the recall of fear memories. Thus, the cerebellum, as well as the amygdala, influences long-term fear memories. These effects are long lasting, as they do not recover over time, even after a reminder shock administration. However, all of the subjects were able to form new fear memories in the absence of inactivation. By increasing the strength of conditioning, we observed that stronger fear memories are affected by the combined but not independent amygdala and cerebellar blockade. These results demonstrate that the cerebellum supports the memory processes even in the absence of a crucial site for emotions like the amygdala. Furthermore, they suggest that the amygdala is only one of the neural sites underlying long-term fear memories. Finally, the inactivation of the perirhinal cortex never alters retrieved fear traces, showing important differences between the amygdala, cerebellum and perirhinal cortex in emotional memories.

Risk factors associated with a high velocity of the development of hyperkalaemia in hospitalised patients

BACKGROUND/OBJECTIVE

Drugs have been recognised as a primary or contributing cause of hyperkalaemia, especially when administered to patients with underlying risk factors. The objective of this study was to analyse the influence of the known risk factors for hyperkalaemia on the velocity of the development of hyperkalaemia.

STUDY DESIGN/METHODS

Clinical characteristics, laboratory data and medication profiles of patients developing hyperkalaemia (serum potassium>or=5.0 mmol/L) hospitalised between 2000 and 2004 in the University Hospital Basel, Switzerland, were recorded. Factors associated with a high velocity of the development of hyperkalaemia were detected using a multiple logistic regression model. Subsequently, the velocity during a defined observation period was compared between patients with one risk factor and patients with two or more risk factors. Finally, the dose effects of drugs identified as risk factors for a high velocity of the development of hyperkalaemia were analysed using two sample comparisons.

RESULTS

A random sample of 551 hospitalised patients was analysed. Compared with the drug treatment at entry, significantly more patients during the hospitalisation were treated with drugs associated with hyperkalaemia, such as heparins (p<0.001), ACE inhibitors or angiotensin receptor blockers (ARBs) [p=0.002], potassium supplements (p<0.001), potassium-sparing diuretics (p<0.001) and/or NSAIDs or selective cyclo-oxygenase (COX)-2 inhibitors (p<0.001). Risk factors associated with a high velocity of the development of hyperkalaemia were use of potassium supplements (adjusted odds ratio [OR] 3.386; 95% CI 2.251, 5.091), severe renal impairment (OR 3.119; 95% CI 2.007, 4.850), use of ACE inhibitors or ARBs (OR 2.642; 95% CI 1.742, 4.006), use of potassium-sparing diuretics (OR 2.065; 95% CI 1.310, 3.254), and diabetes mellitus (OR 1.525; 95% CI 1.005, 2.313). The velocity of the development of hyperkalaemia significantly increased in patients with two or more risk factors. Dose effects could be found for potassium supplements (p=0.006) and potassium-sparing diuretics (p=0.007), but not for ACE inhibitors or ARBs (p=0.289). In contrast, the use of kaliuretics (loop diuretics or thiazides) was associated with a decreased velocity of the development of hyperkalaemia in patients with serious renal impairment (p=0.016) and in patients treated with two or more drug classes associated with a high velocity of the development of hyperkalaemia (p=0.001).

CONCLUSIONS

Risk factors associated with a high velocity of the development of hyperkalaemia are use of potassium supplements>severe renal impairment>use of ACE inhibitors or ARBs>use of potassium-sparing diuretics>diabetes mellitus. The presence of two or more of these risk factors is associated with an even faster development of hyperkalaemia. Clinicians should be aware of these risk factors in order to avoid a rapid development of potentially life-threatening hyperkalaemia.

Prevalence and patient awareness of selected potential drug interactions with self-medication

BACKGROUND AND OBJECTIVE

In community pharmacies potential drug interactions between prescription only medicines (POM) and over-the-counter (OTC) drugs purchased for self-medication arise mainly in two situations: (i) if an OTC drug is purchased by a passer-by customer whose prescribed drug therapy is not known; or (ii) if a POM or an OTC drug is requested by a regular customer whose prescribed drug therapy is usually recorded. With this study we aimed to assess the prevalence of potential drug interactions with selected POM and OTC drugs in passer-by and regular customers as well as their awareness of these potential drug interactions.

METHODS

Data were collected in 14 community pharmacies in the region of Basel, Switzerland by observation of customer contacts and interviews with passer-by customers purchasing selected OTC drugs, and telephone-interviews with regular customers treated with selected POMs identified in community pharmacies' databases. The selected POMs and OTC drugs are drugs which could lead to clinically relevant drug interactions of varying severity but manageable through different interventions such as adjustment of dose and its timing and/or monitoring of the therapy, and avoidance of the combination by choosing an alternative treatment.

RESULTS

Of 1183 passer-by customers observed, 164 (14 x 4%) purchased at least one of the selected OTC drugs. One hundred and two (62 x 2%) of those subjects were interviewed. Forty-three (42 x 2%) mentioned taking prescribed drugs, and three of them were exposed to potential drug interactions of moderate severity. Out of 592 regular customers selected from the community pharmacy database, 434 (73 x 3%) could be interviewed. Sixty-nine (15 x 9%) of them were exposed to a potential drug interaction between purchased OTC drug for self-medication and their POM. Furthermore, 116 (26 x 7%) regular customers were exposed to potential drug interactions within their prescribed drugs and in 28 (6 x 5%) multiple (>or=2) potential drug interactions were found. Two hundred and three (46 x 8%) regular customers were aware of potential drug interactions between their POM and OTC drugs. Ninety-six (47 x 3%) of them were informed by their prescribing physician and 52 (25 x 6%) by their community pharmacist. Awareness of potential drug interaction was higher in younger customers [odds ratio (OR) 0 x 95; 95% confidence intervals (CI) 0 x 93, 0 x 97, P<0 x 0001] and higher for drug interactions classified as 'severe' [OR 1 x 79; 95% CI 1 x 16, 2 x 77, P=0 x 009].

CONCLUSION

Efforts to increase awareness of potential drug interactions is needed. Although community pharmacies are adequately equipped with computerized drug interaction surveillance systems this is often not applied to self-medication. Vigilance for potential interactions of all drugs, including those sold over the counter, should be increased.

Antidepressants as local anesthetics: is there a place in regional anesthesia?

PURPOSE OF REVIEW

Antidepressants have multiple sites of action. Among these, the ability to inhibit sodium channels has led to the increased interest in their use as local anesthetics. The following review summarizes the results of recent studies on this topic.

RECENT FINDINGS

Various animal and human models have shown that antidepressants exhibit many properties of local anesthetics with an extended duration of action. Due to limitations in study designs, however, these dramatic effects might have been misinterpreted and therefore possible toxicity may not have been recognized. Indeed, more recent studies focusing on toxic effects of antidepressants when used as local anesthetics proved this to be the case.

SUMMARY

Although antidepressants indeed act as potent local anesthetics, their use in the clinical setting cannot be recommended as of today due to extensive local tissue toxicity.

Difficulties in maintaining potassium homeostasis in patients with heart failure

Potassium (K) concentration plays a significant role in cell metabolism and membrane excitability. The imbalance of serum potassium is important because it can lead to life-threatening events. Potassium balance may be lost both through the neurohormonal mechanisms involved in cardiovascular diseases and through the drugs used in the treatment of this illness. Avoiding both hypo- and hyperkalemia is beneficial in several cardiovascular diseases, especially heart failure. Electrolyte abnormalities are frequently seen complications in subjects with heart failure. Malignant ventricular arrhythmias and sudden cardiac death are particularly feared complications in K+ instability.

Ranolazine in the management of chronic stable angina

PURPOSE

A review of the pharmacology, pharmacokinetics, clinical trials, safety, and efficacy of ranolazine is presented.

SUMMARY

Ranolazine has recently been approved as adjunctive treatment for chronic stable angina (CSA). Data suggest that ranolazine exerts its antiischemic effect through antagonism of the late sodium current and other cardiac ion channels. Peak plasma levels of ranolazine have been observed two to five hours following repeated dosing and are unaffected by food. In placebo-controlled and active-controlled clinical trials conducted with ranolazine, ranolazine has been effective in the treatment of patients with CSA. One trial demonstrated that monotherapy with extended-release ranolazine was effective against angina and ischemia in patients with CSA. Ranolazine improved exercise duration and time to onset of angina. In a trial in which ranolazine was given in combination with atenolol, diltiazem, or amlodipine, ranolazine produced clinically significant improvement in exercise duration and reduced the incidence of anginal attacks compared with placebo. Another trial demonstrated that extended-release ranolazine 1000 mg given twice daily reduced mean weekly angina episodes in patients with chronic angina. Ranolazine is generally well tolerated. In clinical trials, adverse effects were seen more in the ranolazine groups than in the placebo groups.

CONCLUSION

Despite a lack of mortality data, ranolazine has demonstrated its efficacy and safety, either as monotherapy or in combination with other antianginal agents, in the management of CSA. Patients who fail optimal therapy with standard-of-care antianginal agents are the best candidates for treatment with ranolazine.

Isolated perfused and paced guinea pig heart to test for drug-induced changes of the QT interval

INTRODUCTION

One of the biomarkers for assessing the risk of a cardiac adverse event is drug-induced prolongation of the QT interval. A model is needed for evaluating the potential liability of test compounds on QT interval in vitro. Since QT intervals can be generated from paced or spontaneously beating hearts, data so generated can also be used for validating QT(c) correction equations.

METHODS

Isolated guinea pig hearts were perfused in Locke's solution according to the Langendorff method. QT intervals were routinely measured from Lead II ECG waveforms.

RESULTS

Compounds known to inhibit HERG channel, such as dofetilide, prolonged the QT interval in this model. (+/-)Bay K8644, a calcium channel activator, prolonged the QT interval, while verapamil, a calcium channel blocker, shortened it. Procainamide, a sodium channel blocker, also prolonged the QT interval. Many of the compounds, which prolonged the QT interval, also prolonged PR interval, suggesting dual inhibition of the Ikr channel, the rapid component of delayed rectifier potassium channel, and the calcium channel. The QT/RR intervals exhibited a curvilinear relationship, which could be corrected into nearly straight horizontal lines by using correction equations derived from linear, parabolic, and hyperbolic models. However, these correction equations yielded different results on the QT prolongation produced by sotalol, which also slowed down the heart rate. With the data set obtained in this investigation, correction equations derived from linear and parabolic models worked better than the equations derived from the hyperbolic model. The exponential model did not fit at all.

CONCLUSION

QT intervals obtained under paced conditions provide the most direct and reliable QT information for a drug. The isolated perfused and paced guinea pig heart is a convenient model for studying the effect of compounds on QT interval in vitro.

Pharmacogenetics of antiarrhythmic therapy

Individuals vary widely in their responses to therapy with most drugs. Indeed, responses to antiarrhythmic drugs are so highly variable that study of the underlying mechanisms has elucidated important lessons for understanding variable responses to drug therapy in general. Variability in drug response may reflect variability in the relationship between a drug dose and the concentrations of the drug and metabolite(s) at relevant target sites; this is termed pharmacokinetic variability. Another mechanism is that individuals vary in their response to identical exposures to a drug (pharmacodynamic variability). In this case, there may be variability in the target molecule(s) with which a drug interacts or, more generally, in the broad biological context in which the drug-target interaction occurs. Variants (polymorphisms and mutations) in the genes that encode proteins that are important for pharmacokinetics or for pharmacodynamics have now been described as important contributors to variable drug actions, including proarrhythmia, and these are described in this review. However, the translation of pharmacogenetics into clinical practice has been slow. To this end, the creation of large, well-characterised DNA databases and appropriate control groups, as well as large prospective trials to evaluate the impact of genetic variation on drug therapy, may hasten the impact of pharmacogenetics and pharmacogenomics in terms of delivering personalised drug therapy and to avoid therapeutic failure and serious side effects.

Cibenzoline induced Brugada ECG pattern

We report a case of a 61-year-old female patient who presented with palpitations. The baseline electrocardiogram showed incomplete right bundle branch block with saddle back pattern of the ST segment in one precordial lead, but without any significant ST elevation. She was treated with oral cibenzoline. The subsequent ECG showed a coved Brugada ECG (type I) pattern, which resolved following the discontinuation of cibenzoline. An ajmaline test reproduced the coved type Brugada ECG pattern. Our case is the first report of oral cibenzoline therapy unmasking the diagnostic coved Brugada ECG pattern in a patient with a baseline normal ECG. Cibenzoline, a class I sodium channel blocker antiarrhythmic drug, should probably be avoided in the treatment of patients with Brugada syndrome.

Proarrhythmia as a pharmacogenomic entity: a critical review and formulation of a unifying hypothesis

Proarrhythmia represents an extreme example of the phenomenon that drug effects vary widely among individuals. Studies of mechanisms leading to proarrhythmia have had important implications for understanding arrhythmogenesis, rational use of antiarrhythmic therapies, selection of patients for specific therapies, and drug development. In addition, because proarrhythmia often seems to develop in the absence of clear risk predictors, a role for genetics in predisposing to this adverse drug reaction has been postulated. This review presents mechanisms whereby genetic factors may contribute to variable drug responses and describes our current understanding of how these mechanisms play a role in proarrhythmia. A unifying hypothesis is presented: physiologic processes (such as drug elimination or cardiac repolarization) include multiple redundancies, and congenital or acquired absence of such redundancies--due to disease, interacting drugs, or genetic makeup--may confer no baseline phenotype, but nevertheless enhance susceptibility to unusual drug responses.

Pharmacological concept for topical synergistic analgesia of peripheral neuromuscular pain

A pharmacological concept of topical peripheral pain therapy with a combination of a sodium channel blocker from the class of local anesthetics and a non-steroidal anti-inflammatory drug (NSAID) from the class of nonselective/ partially selective cyclooxygenase (COX) inhibitors is described. The dual mechanism of action of these substances on the cellular level interferes with pain components of both inflammatory and neuronal genesis and is functionally synergistic. This enables the combination of these agents to produce a more long-lasting analgesia than is attainable with either of the substances alone. The therapeutic indication is the symptomatic reduction of neuromuscular pain of traumatic or metabolic origin. The already more favorable safety profile for topical applications can be improved further by a possible dose reduction of the two substances.

A Critical Reconsideration of the Clinical Effects and Treatment Recommendations for Sodium Channel Blocking Drug Cardiotoxicity

The cardiac sodium channel is comprised of proteins that span the cardiac cell membrane and form the channel pore. Depolarisation causes the proteins to move and open the sodium channel. Once the channel is open (active conformation), sodium ions move into the cell. The channel then changes from the active conformation to an inactive conformation - the channel remains open, but influx of sodium ions ceases. Recovery occurs as the channel moves from the inactive conformation back to the closed conformation and is then ready to open following the next depolarisation. Sodium channel blocking drugs (NCBDs) occupy receptors in the channel during the active and inactive conformations. The drug dissociates from most of the channel receptors during recovery, but the time it takes the drug to dissociate slows recovery. The slowed recovery prolongs conduction time, the main toxicity of NCBD overdose. Conduction time is further prolonged if heart rate increases as there are more available active and inactive conformations/unit time, which increases channel receptor binding sites for the NCBD. In addition to prolonging conduction time, NCBDs also decrease inotropy. Treatment of NCBD cardiotoxicity has been based on in vitro and animal experiments, and case reports. Assumptions based on this evidence must now be reassessed. For example, canines consistently develop ventricular tachycardia (VT) when tricyclic antidepressants (TCAs) are administered. Much of the literature discussing NCBD cardiotoxicity assumes that TCA poisoning induces VT in humans with the same regularity that occurs in canines. Seemingly, in support of this assumption was the finding that patients with remote myocardial infarction developed VT when therapeutically ingesting a NCBD. However, conduction is prolonged in myocardium that is or has been ischaemic. NCBD prolong conduction more in previously ischaemic myocardium than in normal myocardium, which causes nonuniform conduction and allows the development of re-entrant arrhythmias such as VT. Although some nonuniform conduction may occur in the healthy heart following a NCBD overdose, there is no evidence that nonuniform conduction occurs to the extent that it will cause re-entrant arrhythmias in this setting. Using various animal models and a variety of NCBDs, sodium ions, bicarbonate ions and alkalosis have been compared for the treatment of ventricular arrhythmias, hypotension and mortality. The results of these experiments have been extrapolated to NCBD overdose in humans. Animal models and single treatment approaches may have narrowed our scope. More recent evidence indicates that properties of each individual NCBD may require unique treatment. There is limited evidence that glucagon, which increases initial sodium ion influx into the cardiac cell, should be considered early in the treatment of cardiotoxicity. Another consideration may be treatment of NCBD with faster kinetics. Conduction time is decreased if a NCBD occupying the receptor is replaced by a NCBD that moves off and on the receptor more quickly. There is less evidence for this treatment, as risk may be greater. With greater understanding of the sodium channel and NCBDs, we must reassess our approach to the treatment of patients with healthy hearts who overdose on NCBD.

Wide-complex tachycardia: beyond the traditional differential diagnosis of ventricular tachycardia vs supraventricular tachycardia with aberrant conduction

Wide-complex tachycardia (WCT) is defined as a rhythm disturbance with a rate greater than 100 beats/min and a QRS complex duration of 0.12 seconds or more in the adult patient; in the pediatric patient, both rate and QRS complex width are age related. In evaluating this type of tachycardia, there are 2 broad categories usually discussed in the medical literature: ventricular and supraventricular with aberrant intraventricular conduction. There are several other important causes of a WCT encountered in clinical practice, which are less often discussed; these tachycardias often require specific therapies differing from the standard approach to WCT. These tachycardias are diverse; as such, the pathophysiology behind each form of WCT includes toxic, metabolic, and conduction system dysfunction mechanisms.

Long-term efficacy of hybrid pharmacologic and ablation therapy in patients with pilsicainide-induced atrial flutter

BACKGROUND

Combination therapy with catheter ablation of the cavo-tricuspid isthmus and continued drug therapy, that is, "hybrid therapy," in patients with atrial fibrillation (AF) and drug-induced atrial flutter (AFL) is reported to be an alternative means of achieving and maintaining sinus rhythm. With respect to choosing this method among the rhythm control therapies, its long-term efficacy and the prevalence of AFL in patients with AF are very important and have not been fully elucidated.

HYPOTHESIS

The purpose of this study was to investigate the long-term effectiveness of this hybrid therapy and the dose prevalence in Ic drug-induced AFL.

METHODS

The subjects were 89 patients (aged 62.4 years, 72 men) with episodes of AF (paroxysmal type: 65, persistent type: 11, permanent type: 13). After 4 weeks of oral pilsicainide administration, the dose was increased in those with no documented AFL. The patients who experienced AFL with pilsicainide (Ic-AFL) underwent ablation.

RESULTS

Pilsicainide administration resulted in the common type AFL in 17 patients (19.1%). The pilsicainide plasma concentration in the patients with Ic-AFL was significantly higher than in those without AFL (0.79 +/- 0.41 vs. 0.51 +/- 0.24 microg/ml, respectively, p < 0.01). During a 10-54 (mean 37 +/- 14) month follow-up period, sinus rhythm was maintained in 10 of 12 patients after successful ablation followed by continued antiarrhythmic drug administration.

CONCLUSIONS

Hybrid therapy with ablation and high doses of pilsicainide was useful in maintaining sinus rhythm in some selected patients with AF and drug-induced AFL.

Improvement of motor function in early Parkinson disease by safinamide

A median safinamide (SAF) dose of 70 mg/day (range 40 to 90 mg/day) increased the percentage of parkinsonian patients improving their motor scores by > or =30% from baseline (responders) after 3 months from 21.4% (placebo) to 37.5% (p < 0.05, calculated by logistic regression analysis). In a subgroup of 101 patients under stable treatment with a single dopamine agonist, addition of SAF magnified the response (47.1% responders, mean 4.7-point motor score decrease; p > or = 0.05). These results suggest that doses of SAF exerting ion channel block and glutamate release inhibition add to its symptomatic effect and warrant exploration of higher doses.