Block of the delayed rectifier current (IK) by the 5-HT3 antagonists ondansetron and granisetron in feline ventricular myocytes

A case-control study on the clinical characteristics of granisetron-related arrhythmias and the development of a predictive nomogram

BACKGROUND

Automatic monitoring and assessment are increasingly employed in drug safety evaluations using hospital information system data. The increasing concern about granisetron-related arrhythmias requires real-world studies to improve our understanding of its safety.

AIM

This study aimed to analyze the incidence, clinical characteristics, and risk factors of granisetron-related arrhythmias in hospitalized patients using real-world data obtained from the Adverse Drug Event Active Surveillance and Assessment System-II (ADE-ASAS-II) and concurrently aimed to develop and validate a nomogram to predict the occurrence of arrhythmias.

METHOD

Retrospective automatic monitoring of inpatients using granisetron was conducted in a Chinese hospital from January 1, 2017, to December 31, 2021, to determine the incidence of arrhythmias using ADE-ASAS- II. Propensity score matching was used to balance confounders and analyze clinical characteristics. Based on risk factors identified through logistic regression analysis, a prediction nomogram was established and internally validated using the Bootstrap method.

RESULTS

Arrhythmias occurred in 178 of 72,508 cases taking granisetron with an incidence of 0.3%. Independent risk factors for granisetron-related arrhythmias included medication duration, comorbid cardiovascular disease, concomitant use of other 5-hydroxytryptamine 3 receptor antagonists, alanine aminotransferase > 40 U/L, and blood urea nitrogen > 7.5 mmol/L. The nomogram demonstrated good differentiation and calibration, with enhanced clinical benefit observed when the risk threshold ranged from 0.10 to 0.82.

CONCLUSION

The nomogram, based on the five identified independent risk factors, may be valuable in predicting the risk of granisetron-related arrhythmias in the administered population, offering significant clinical applications.

Ondansetron and teratogenicity in rats: Evidence for a mechanism mediated via embryonic hERG blockade

The potent hERG channel blocking drug ondansetron is used off-label for treatment of nausea and vomiting in early pregnancy. Some human epidemiological studies have associated ondansetron with fetal cardiovascular defects and orofacial clefts. This study investigated the effects of ondanestron on embryonic heart rhythm of gestational day (GD) 13 rat embryos in vitro and then integrated the results with published animal teratology, and animal and human pharmacokinetic studies to perform a risk evaluation. Ondansetron caused concentration dependent bradycardia and arrhythmia. Cardiovascular malformations in rats occurred at exposures slightly higher than those in early human pregnancy. Together the results suggest that ondansetron can have teratogenic potential in rats and humans mediated via hERG block and severe heart rhythm disturbances in the embryo. The risk may be increased in human pregnancy if additional risk factors are present such as hypokalemia.

Ondansetron blocks wild-type and p.F503L variant small-conductance Ca2+-activated K+ channels

Apamin-sensitive small-conductance Ca2+-activated K+ (SK) current ( IKAS) is encoded by Ca2+-activated K+ channel subfamily N ( KCNN) genes. IKAS importantly contributes to cardiac repolarization in conditions associated with reduced repolarization reserve. To test the hypothesis that IKAS inhibition contributes to drug-induced long QT syndrome (diLQTS), we screened for KCNN variants among patients with diLQTS, determined the properties of heterologously expressed wild-type (WT) and variant KCNN channels, and determined if the 5-HT3 receptor antagonist ondansetron blocks IKAS. We searched 2,306,335 records in the Indiana Network for Patient Care and found 11 patients with diLQTS who had DNA available in the Indiana Biobank. DNA sequencing discovered a heterozygous KCNN2 variant (p.F503L) in a 52-yr-old woman presenting with corrected QT interval prolongation at baseline (473 ms) and further corrected QT interval lengthening (601 ms) after oral administration of ondansetron. That patient was also heterozygous for the p.S38G and p.P2835S variants of the QT-controlling genes KCNE1 and ankyrin 2, respectively. Patch-clamp experiments revealed that the p.F503L KCNN2 variant heterologously expressed in human embryonic kidney (HEK)-293 cells augmented Ca2+ sensitivity, increasing IKAS density. The fraction of total F503L-KCNN2 protein retained in the membrane was higher than that of WT KCNN2 protein. Ondansetron at nanomolar concentrations inhibited WT and p.F503L SK2 channels expressed in HEK-293 cells as well as native SK channels in ventricular cardiomyocytes. Ondansetron-induced IKAS inhibition was also demonstrated in Langendorff-perfused murine hearts. In conclusion, the heterozygous p.F503L KCNN2 variant increases Ca2+ sensitivity and IKAS density in transfected HEK-293 cells. Ondansetron at therapeutic (i.e., nanomolar) concentrations is a potent IKAS blocker. NEW & NOTEWORTHY We showed that ondansetron, a 5-HT3 receptor antagonist, blocks small-conductance Ca2+-activated K+ (SK) current. Ondansetron may be useful in controlling arrhythmias in which increased SK current is a likely contributor. However, its SK-blocking effects may also facilitate the development of drug-induced long QT syndrome.

Drug utilization in emergency medicine department at a tertiary care teaching hospital: A prospective study

Background and Objectives:

The practice of emergency medicine has the primary mission of evaluating, managing and providing treatment to those patients with unexpected injury or illness. Instituting appropriate therapy is necessary for safety of the patients and to decrease mortality and morbidity. The objectives were to study the drug utilization pattern and direct cost of therapy in emergency medicine department of a tertiary care teaching hospital.

Materials and Methods:

Data of the patients admitted to emergency medicine department was collected prospectively for 48 h from the time of admission over 2 months. The prescriptions were analyzed for drug use pattern and direct cost of therapy was calculated.

Results:

A total of 156 patients received 1635 drugs with the mean of 9.99 ± 2.55 drugs/patient. Most common diagnosis was acute coronary syndrome 35 (21.79%). Ondansetron 135 (86.53%) was most frequently prescribed drug followed by pantoprazole 133 (85.25%) and furosemide 68 (43.58%). Amongst antimicrobials ceftriaxone 51 (32.69%) was the most commonly prescribed drug. Direct cost of treatment per patient for the first 48 h was र 4051 ± 1641.

Conclusion:

Ondansetron and pantoprazole were the most commonly prescribed drugs in the emergency department. However, their use in all patients was not justified. Polypharmacy was prevalent. A closer look at the rationality of therapy would help in highlighting issues involved and would be helpful to authorities in deciding prescribing policies.

Ondansetron and granisetron binding orientation in the 5-HT(3) receptor determined by unnatural amino acid mutagenesis

The serotonin type 3 receptor (5-HT(3)R) is a ligand-gated ion channel found in the central and peripheral nervous systems. The 5-HT(3)R is a therapeutic target, and the clinically available drugs ondansetron and granisetron inhibit receptor activity. Their inhibitory action is through competitive binding to the native ligand binding site, although the binding orientation of the drugs at the receptor has been a matter of debate. Here we heterologously express mouse 5-HT(3)A receptors in Xenopus oocytes and use unnatural amino acid mutagenesis to establish a cation-π interaction for both ondansetron and granisetron to tryptophan 183 in the ligand binding pocket. This cation-π interaction establishes a binding orientation for both ondansetron and granisetron within the binding pocket.

Ondansetron-associated hypokalemia in a 2-year-old with pre-B-cell ALL

Ondansetron is a commonly used medication in the treatment of nausea and vomiting arising from many etiologies, including chemotherapy. Although it is a highly safe drug, ondansetron use has been associated, rarely, with hypokalemia. However, it is unknown whether hypokalemia is due to the medication itself or to an underlying potassium disturbance caused by prior metabolic derangements, including vomiting. We relate a patient who presents with hypokalemia of unknown etiology, with evidence suggesting a possible relationship to ondansetron. We also present a proposed mechanism for this phenomenon.

Electrocardiographic and cardiovascular effects of the 5-hydroxytryptamine3 receptor antagonists

OBJECTIVE

To review the electrocardiographic (ECG) and cardiovascular effects of 5-hydroxytryptamine(3) (5-HT(3)) receptor antagonists preclinically, in healthy volunteers, and in patients undergoing chemotherapy or surgery.

DATA SOURCES

A MEDLINE search was performed of clinical trials and preclinical data published between 1963 and December 2002 assessing the ECG and cardiovascular effects of 5-HT(3) receptor antagonists, supplemented with reviews and secondary sources.

STUDY SELECTION AND DATA EXTRACTION

All of the articles identified were evaluated and all information deemed relevant was included in this review.

DATA SYNTHESIS

There are no clinically relevant differences in efficacy and safety among the available 5-HT(3) receptor antagonists for prevention and treatment of chemotherapy-induced and postoperative nausea and vomiting. As a class, they have well-defined electrophysiologic activity. Changes in ECG parameters (PR, QRS, QT, QTc, JT intervals) are small, reversible, clinically insignificant, and independent of the patient population studied, and patients are asymptomatic during these changes. ECG changes are most prominent 1-2 hours after a dose of dolasetron, ondansetron, and granisetron and return to baseline within 24 hours. Clinically important adverse cardiovascular events associated with these changes are rare. No serious cardiac events (including torsade de pointes) arising from ECG interval changes have been attributed to 5-HT(3) receptor antagonist use.

CONCLUSIONS

Clinical data demonstrate that ECG interval changes are a class effect of the 5-HT(3) receptor antagonists. Theoretical concern regarding cardiovascular adverse events with these agents is not supported by clinical experience. The significant benefits of these agents outweigh the theoretical small risk of meaningful cardiovascular events.

Structural and functional basis for the long QT syndrome: relevance to veterinary patients

Long QT syndrome (LQTS) is a condition characterized by prolongation of ventricular repolarization and is manifested clinically by lengthening of the QT interval on the surface ECG. Whereas inherited forms of LQTS associated with mutations in the genes that encode ion channel proteins are identified only in humans, the acquired form of LQTS occurs in humans and companion animal species. Often, acquired LQTS is associated with drug-induced block of the cardiac K+ current designated I(Kr). However, not all drugs that induce potentially fatal ventricular arrhythmias antagonize I(Kr), and not all drugs that block I(Kr), are associated with ventricular arrhythmias. In clinical practice, the extent of QT interval prolongation and risk of ventricular arrhythmia associated with antagonism of I(Kr) are modulated by pharmacokinetic and pharmacodynamic variables. Veterinarians can influence some of the potential risk factors (eg, drug dosage, route of drug administration, presence or absence of concurrent drug therapy, and patient electrolyte status) but not all (eg, patient gender/genetic background). Veterinarians need to be aware of the potential for acquired LQTS during therapy with drugs identified as blockers of HERG channels and I(Kr).

Potent antagonism of 5-HT(3) and 5-HT(6) receptors by olanzapine

The interaction of the psychotropic agent olanzapine with serotonin 5-HT(3) and 5-HT(6) receptors was investigated. Olanzapine did not contract the isolated guinea pig ileum, but blocked contractions induced by the 5-HT(3) receptor agonist 2-methyl serotonin (2-CH(3) 5-HT) with a pK(B) value of 6.38+/-0.03, close to the affinity of the 5-HT(3) receptor antagonist ondansetron. The atypical antipsychotic risperidone (1 microM) did not significantly inhibit 2-CH(3) 5-HT-induced contractions. Olanzapine had high affinity (pK(i)=8.30+/-0.06) for human 5-HT(6) receptors in radioligand binding studies. Olanzapine did not stimulate [35S]guanosine-5'-O-(3-thio)triphosphate ([35S]GTPgammaS) binding to the G protein G(s) in cells containing human 5-HT(6) receptors, but inhibited 5-HT-stimulated [35S]GTPgammaS binding (pK(B)=7.38+/-0.16). Among other antipsychotics investigated, clozapine antagonized 5-HT(6) receptors with a pK(B)=7.42+/-0.15, ziprasidone was three-fold less potent, and risperidone, quetiapine and haloperidol were weak antagonists. Thus, olanzapine was not an agonist, but was a potent antagonist at 5-HT(6) receptors and had marked antagonism at 5-HT(3) receptors.

Single-blind study of the effects of intravenous dolasetron mesylate versus ondansetron on electrocardiographic parameters in normal volunteers

A single-blind, randomized, five-way cross-over, safety and tolerability trial was conducted to determine whether intravenous (i.v.) dolasetron mesylate at varying single doses induces changes in ECG intervals in healthy volunteers and to compare these changes with a single intravenous dose of ondansetron or placebo. Thirty healthy male volunteers received 1.2, 1.8, and 2.4 mg/kg i.v. dolasetron mesylate, 32 mg i.v. ondansetron, and placebo on 5 separate days. ECGs were recorded at intervals during the 24 h after study drug administration. The changes in ECG intervals observed after dolasetron mesylate or ondansetron were acute, transient, and asymptomatic. Dolasetron mesylate resulted in slight but statistically significant dose-related increases in heart rate (HR) and PR and QRS intervals (between h 0 and 4). A statistically significant increase in QTc interval was detected with both dolasetron mesylate (2.4 mg/kg) and ondansetron. Ondansetron also produced a slight but statistically significant increase in JT interval and a decrease in HR. These changes in ECG intervals were usually observed between h 0 and 4; all parameters returned to baseline within 8 h of treatment. The results demonstrate that both dolasetron mesylate and ondansetron prolong the QTc interval. However, dolasetron mesylate predominantly altered ECG parameters indicative of ventricular depolarization (QRS duration), whereas ondansetron predominantly affected ventricular repolarization as measured by a prolongation in the JT interval. Both dolasetron and ondansetron were well tolerated. The adverse event (AE) rate was 13.3% (4 of 30); all AE were of mild or moderate severity and were distributed across all dose arms.

Serotonin and protein kinase C modulation of a rat brain inwardly rectifying K+ channel expressed in xenopus oocytes

In Xenopus laevis oocytes injected with rat brain poly(A)+ RNA, perfusion with a high-K+ solution (96 mM KCl) generated an inward current (IHK) which was absent in water-injected oocytes. Part of IHK was blocked by low concentrations of Ba2+ (half-maximal inhibitory concentration, IC50: 4.2 +/- 0.5 microM). When serotonin (5-HT) was applied to these oocytes a transient inward oscillating Cl- current arising from activation of Ca2+ -dependent Cl- channels, ICl (Ca), was observed. When this response decayed, a 30% reduction of IHK could be detected. Electrophysiological characterization of the K+ channel down-modulated by 5-HT revealed that it is an inward rectifier. Anti-sense suppression experiments revealed that the 5-HT2C receptor mediates the down-modulatory effect of 5-HT. The nature of the modulatory pathway was investigated by application of phorbol esters and intracellular injection of protein kinase C (PKC) inhibitors, ethylenebis (oxonitrilo)tetraacetate (EGTA) and inositol 1,4,5-trisphosphate. The results demonstrate that PKC is responsible for the down-modulatory effect.