Embryo-fetal safety evaluation of ondansetron in rats.

BACKGROUND: Ondansetron is a 5HT3 receptor antagonist, used to mitigate the effects of nausea and vomiting after chemotherapy or surgery. Since nausea and vomiting are common experiences during the first trimester of pregnancy, this antiemetic has been the main drug used during this period. METHODS: To evaluate the effects of ondansetron on the embryo-fetal development, which are still very contradictory, pregnant rats were exposed to therapeutic doses of ondansetron (1.7 or 2.5 mg/kg) daily, from gestational day (GD) 6 to 15. RESULTS: No clinical signs of toxicity were observed in dams during the treatment. Although the hemato-biochemical parameters were similar among the groups, histological changes, as well as a reduction in the weight of kidney were found in the treated dams. After fetal examination, no visceral and skeletal abnormalities were observed in treated fetuses. CONCLUSION: In conclusion, therapeutic doses of ondansetron have low teratogenic potential in rats. These data provide important information about the drug safety during pregnancy.

Pregnancy outcome following in-utero exposure to ondansetron: A prospective comparative observational study.

The objective of the study was to evaluate the rate of major congenital anomalies after first trimester exposure to ondansetron for nausea and vomiting of pregnancy (NVP). The design is a prospective, comparative, observational cohort study, performed at the Israeli Teratology Information Service between 2010 and 2014. Follow-up was obtained for 195 ondansetron-exposed, 110 metoclopramide-exposed, and 778 pregnancies with non-teratogenic exposure (NTE). The overall rate of major anomalies did not significantly differ between the groups [4/200 = 2.0 % (ondansetron), 1/109 = 0.9 % (metoclopramide), and 13/731 = 1.8 % (NTE)]. All the anomalies in both the ondansetron and metoclopramide groups, and 6/13 anomalies in the NTE group, were cardiac septal defects most of which spontaneously resolved. Both ondansetron (adjHR = 0.29, 95 % CI 0.10-0.80) and metoclopramide (adjHR = 0.27, 95 % CI 0.08-0.86) were associated with lower miscarriage rate compared to NTE. Based on the present study, ondansetron during pregnancy is not associated with an increased risk for overall major anomalies, nor for clinically important cardiac defects. It may be a reasonable alternative for women with severe NVP who do not respond to first line medications.

Major Congenital Malformation Risk After First Trimester Gestational Exposure to Oral or Intravenous Ondansetron.

Ondansetron is a 5-HT3 receptor antagonist that has been approved for the prevention of nausea and vomiting associated with cancer chemotherapy, radiotherapy, and surgery. Ondansetron has also been studied in the treatment of many neuropsychiatric and medical conditions. The drug is commonly used off-label to treat nausea and vomiting of pregnancy (NVP) and hyperemesis gravidarum (HG). Ondansetron crosses the placental barrier, and concerns have been expressed that using ondansetron for NVP/HG during the first trimester of pregnancy may increase the risk of major congenital malformations (MCMs) in the offspring. In this context, findings from a meta-analysis of 6 cohort and 2 case-control studies, read along with the results of subsequently published cohort (n = 3) and case-control (n = 1) studies, suggest that a signal does exist to associate early gestational exposure to ondansetron with an increased risk of heart defects and orofacial defects. Arguments both for and against confounding by indication have been proposed to explain these findings. Nevertheless, even if ondansetron is causally implicated in MCM risk, the absolute increase in risk, such as for orofacial clefts (by 0.03%) and ventricular septal defect (by 0.3%), is small. These small risks should be balanced against the risks associated with inadequately treated NVP/HG, and decision-making must be shared between clinician and patient. Repeated fetal scanning during the second trimester can help in the early detection of malformations, if present.

The effect of anti-emetic drugs on rat embryonic heart activity.

Nausea and vomiting of pregnancy (NVP) is the most common medical complaint during pregnancy affecting up to 70% of pregnant women worldwide. Some antiemetic medications (AEM) (droperidol, domperidone, granisetron, metoclopramide and trifluoperazine) used to treat NVP have the unwanted side effect of hERG blockade. The hERG potassium channel is essential for normal heart rhythm in both the adult human and the human and rat embryo. Animal studies show hERG blockade in the embryo causes bradycardia and arrhythmia leading to cardiovascular malformations and other birth defects. Whole rat embryo in vitro culture was used to determine the effect of the above listed AEM and meclizine on the heart rate of Gestational day 13 rat embryos. These embryos are similar in size and heart development to 5-6-week human embryo. The results showed that all of the AEMs caused a concentration-dependent bradycardia. Droperidol had the lowest margin of safety.

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.

Analysis of Toxicity Effects of Buspirone, Cetirizine and Olanzapine on Human Blood Lymphocytes: in Vitro Model.

BACKGROUND: The current study investigates the cytotoxicity mechanism of common drugs with piperazine ring such as cetirizine, olanzapine and buspirone on human lymphocytes. METHODS: The viability of lymphocytes, reactive oxygen species (ROS) formation, mitochondrial membrane potential (MMP) collapse, lysosomal integrity, content of glutathione and lipid peroxidation was determined. RESULTS: Buspirone and cetirizine showed more toxicity than olanzapine on human lymphocytes with an IC50 value of 200 µg/ml, after 6 h of incubation. Significant ROS formation, MMP collapse, lipid peroxidation, lysosomal damage and elevation of glutathione disulfide (GSSG) were observed in treated lymphocytes concentrations (4, 20, 40 µg/ml) of buspirone and cetirizine. CONCLUSION: Our results show the exposure of human lymphocytes with buspirone and cetirizine, which usually happens during the poisoning, triggers oxidative stress and organelle damages. Our study suggests that using antioxidants, mitochondrial and lysosomal protective agents can protect blood lymphocytes, from probable side effects of these highly consumed medications.

Severe Proarrhythmic Potential of the Antiemetic Agents Ondansetron and Domperidone.

The potential of ondansetron and domperidone, both clinically established antiemetic agents, to increase the QT-interval has been described in several case reports. Therefore, the aim of the present study was to investigate whether these drugs may provoke polymorphic ventricular tachycardia in a sensitive experimental model of drug-induced proarrhythmia. In 10 female rabbits, ondansetron (1, 5 and 10 µM, n = 10) or domperidone (0.5, 1 and 2 µM, n = 8) was infused after obtaining baseline data. Eight endo- and epicardial monophasic action potentials and a simultaneously recorded 12-lead ECG reproduced the clinically observed QT-prolongation (ondansetron: 1 µM:+17 ms, 5 µM:+41 ms, 10 µM:+78 ms, p < 0.01; domperidone: 0.5 µM:+57 ms, 1 µM:+79 ms, 2 µM:+99 ms, p < 0.01). This was accompanied by a significant increase in action potential duration at 90% of repolarization. Administration of both agents also increased dispersion of repolarization (ondansetron: 1 µM:+12 ms, 5 µM:+17 ms; 10 µM:+18 ms, p < 0.05; domperidone: 0.5 µM:+19 ms, 1 µM:+27 ms; 2 µM:+23 ms p < 0.05). Lowering of potassium concentration in bradycardic AV-blocked hearts provoked early afterdepolarizations (EADs) in 9 of 10 ondansetron-treated hearts and induced polymorphic ventricular tachycardia (VT) resembling torsade de pointes in 7 of 10 ondansetron-treated hearts (86 episodes). Under the influence of domperidone, EAD and polymorphic VT occurred in 7 of 8 hearts (131 episodes). In the present study, both ondansetron and domperidone demonstrated a severe proarrhythmic potential. A significant prolongation of cardiac repolarization as well as a marked increase in spatial dispersion of repolarization represents the underlying electrophysiologic mechanisms. These results imply that application of ondansetron should be handled carefully. For regular administration, ECG monitoring should be mandatory.

Publishing negative findings and the challenge of avoiding type II errors in studies of suspect teratogens: Example of a recent ondansetron publication.

It is important that negative, as well as positive, studies be published to complete the available picture in areas of scientific inquiry. At the same time, it is critical that the implications of a negative study not be overstated and generalized when major issues of study design and data accuracy may be the reason that no relationship was discovered. The challenge of avoiding type II errors in interpreting negative findings has major public health implications, especially when the relationship of an exposure to birth defects is the concern. This is particularly important when interpreting the report by Fazio et al. (June issue of Reproductive Toxicology) on the relationship of ondansetron exposure to pregnancy outcome and birth defects. This review addresses the study design and conclusions and suggests that an alternative concluding statement would be more apropos, given the limitations of the data.

Cardiotoxic Antiemetics Metoclopramide and Domperidone Block Cardiac Voltage-Gated Na+ Channels.

BACKGROUND: Metoclopramide and domperidone are prokinetic and antiemetic substances often used in clinical practice. Although domperidone has a more favorable side effect profile and is considered the first-line agent, severe cardiac side effects were reported during the administration of both substances. Cardiac Na channels are common targets of therapeutics inducing cardiotoxicity. Therefore, the aim of this study was to investigate whether the differential cardiotoxicities of metoclopramide and domperidone correlate with the block of Na channels. METHODS: Effects of metoclopramide and domperidone on the human α-subunit Nav1.5 expressed in human embryonic kidney 293 cells and on Na currents in neonatal rat cardiomyocytes were investigated by means of whole-cell patch clamp recordings. RESULTS: Tonic block of resting Nav1.5 channels was more potent for domperidone (IC50 85 ± 25 µM; 95% confidence interval [CI], 36-134) compared with metoclopramide (IC50 458 ± 28 µM; 95% CI, 403-513). Both agents induced use-dependent block at 10 and 1 Hz, stabilized fast and slow inactivation, and delayed recovery from inactivation. However, metoclopramide induced considerably smaller effects compared with domperidone. Na currents in rat cardiomyocytes displayed tonic and use-dependent block by both substances, and in this system, domperidone (IC50 312 ± 15 µM; 95% CI, 22-602) and metoclopramide (IC50 250 ± 30 µM; 95% CI, 191-309) induced a similar degree of tonic block. CONCLUSIONS: Our data demonstrate that the clinically relevant cardiotoxicity of domperidone and metoclopramide corresponds to a rather potent and local anesthetic-like inhibition of cardiac Na channels including Nav1.5. These data suggest that Nav1.5 might be a hitherto unrecognized molecular mechanism of some cardiovascular side effects, for example, malignant arrhythmias of prokinetic and antiemetic agents.

Evaluating the potential effect on fetal tissue after exposure to granisetron during pregnancy.

The objective of this study was to elucidate the possible toxic effects on the fetal tissues after exposure to two clinically relevant concentrations of granisetron. Primary cells were isolated from human fetal organs of 16-19 weeks gestational age and treated with 3 ng/mL or 30 ng/mL of granisetron. Cell cycle progression was evaluated by flow cytometry. ELISA was used to detect alterations in major apoptotic proteins. Up to 10% apoptosis in cardiac tissue was observed following treatment with 30 ng/mL granisetron. Neither concentration of granisetron caused alteration in cell cycle progression or alterations in apoptotic proteins in any of the other tissues. At 30 ng/mL granisetron concentration had the potential to induce up to 10% apoptosis in cardiac tissue; clinical significance needs further evaluation. At granisetron 3 ng/mL there was no detectable toxicity or on any fetal tissue in this study. Further research is needed to confirm these preliminary findings and determine if clinically significant.

Gastrointestinal toxicity after vincristine or cyclophosphamide administered with or without maropitant in dogs: a prospective randomised controlled study.

OBJECTIVES: To assess the prevalence of gastrointestinal toxicity in dogs receiving chemotherapy with vincristine and cyclophosphamide and the efficacy of maropitant citrate (Cerenia™, Zoetis) in reducing these events. METHODS: Dogs receiving chemotherapy with cyclophosphamide or vincristine were randomised to either receive maropitant or not in the period immediately after treatment and for 4 days afterwards. Owners completed a diary of adverse events following treatment. RESULTS: Adverse events occurred in 40/58 (69%) dogs in the vincristine group. Most of these adverse events were mild and included: lethargy (62%), appetite loss (43%), diarrhoea (34%) and vomiting (24%). Adverse events occurred in 34/42 (81%) dogs treated with cyclophosphamide. Most of these adverse events were mild and included: lethargy (62%), diarrhoea (36%), appetite loss (36%) and vomiting (21%). There was no difference in total clinical score, vomiting, diarrhoea, appetite loss or lethargy score between dogs treated with maropitant and non-treated dogs in either the vincristine or cyclophosphamide groups. CLINICAL SIGNIFICANCE: Chemotherapy-related side effects are frequent but usually mild in dogs receiving vincristine or cyclophosphamide. Prophylactic administration of maropitant does not reduce the frequency of adverse events and maropitant should be administered only as required for individual cases.

[How safe are dimenhydrinate suppositories?]. / Wie sicher sind Dimenhydrinat-Suppositorien?

HISTORY: A 13-month-old girl suffered from 3 generalized tonic-clonic seizures for several minutes within a total period of 9 hours. History revealed that the child received a total of 5 dimenhydrinate containing suppositories à 40 mg during the previous 2 days (i. e. 23 mg dimenhydrinate per kg body weight) due to enteritis with vomiting. The first seizure occurred 10 hours after the last administration. INVESTIGATIONS: The plasma level of diphenhydramin was 230 µg/l approximately one hour after the first seizure. Electroencephalography showed no pathological signs, an MRI scan of the brain was normal except of several small gliotic spots and body temperature was regularly. TREATMENT AND COURSE: Two stationary occurring seizures were stopped with 5 mg diazepam rectally. Continued surveillance and an EEG two days later showed age-appropriate normal findings. There were no further seizures in the next 4 years. CONCLUSION: Infants have the risk to develop dimenhydrinate intoxication, especially in cases where suppositories were given repeatedly because of intermittent defecation.

Investigation of developmental toxicity and teratogenicity of antiemetics on rat embryos cultured in vitro.

In this study, we aimed to investigate and compare the direct toxic and teratogenic effects of dimenhydrinate, metoclopramide and trimethobenzamide HCl, antiemetic drugs on embryonic growth and development in cultured rat embryos. Embryos were explanted on day 9.5 of gestation and cultured. Whole rat serum was used as a culture medium for the control group while different concentrations of dimenhydrinate (2.5-20 µg/ml), metoclopramide (10-50 µg/ml) and trimethobenzamide HCl (25-100 µg/ml) were added to serum for the experimental groups. Effects of antiemetics on embryonic developmental parameters were compared, and embryos were evaluated for the presence of any malformations. Also, the total DNA was extracted from the cells to determine the fragmentation of nuclear DNA of embryonic cells. Compared with the control embryos, the antiemetics significantly decreased all growth and developmental parameters dose dependently. There was no difference regarding the fragmentation of nuclear DNA of the all used agents and controls. Amongst the agents, trimethobenzamide HCl was found to have more toxic and teratogenic potential, and metoclopramide appears to be the least toxic antiemetic and therefore could be more safely used and might be preferred for the treatment of nausea and vomiting in pregnancy.

Anti-emetic and emetic effects of erythromycin in Suncus murinus: role of vagal nerve activation, gastric motility stimulation and motilin receptors.

Paradoxically, erythromycin is associated with nausea when used as an antibiotic but at lower doses erythromycin activates motilin receptors and is used to treat delayed gastric emptying and nausea. The aim of this study was to characterise pro- and anti-emetic activity of erythromycin and investigate mechanisms of action. Japanese House musk shrews (Suncus murinus) were used. Erythromycin was administered alone or prior to induction of emesis with abnormal motion or subcutaneous nicotine (10mg/kg). The effects of erythromycin and motilin on vagal nerve activity and on cholinergically mediated contractions of the stomach (evoked by electrical field stimulation) were studied in vitro. The results showed that erythromycin (1 and 5mg/kg) reduced vomiting caused by abnormal motion (e.g., from 10.3 ± 1.8 to 4.0 ± 1.1 emetic episodes at 5mg/kg) or by nicotine (from 9.5 ± 2.0 to 3.1 ± 2.0 at 5mg/kg), increasing latency of onset to emesis; lower or higher doses had no effects. When administered alone, erythromycin 100mg/kg induced vomiting in two of four animals, whereas lower doses did not. In vitro, motilin (1, 100 nM) increased gastric vagal afferent activity without affecting jejunal afferent mesenteric nerve activity. Cholinergically mediated contractions of the stomach (prevented by tetrodotoxin 1 µM or atropine 1 µM, facilitated by l-NAME 300 µM) were facilitated by motilin (1-100 nM) and erythromycin (10-30 µM). In conclusion, low doses of erythromycin have anti-emetic activity. Potential mechanisms of action include increased gastric motility (overcoming gastric stasis) and/ or modulation of vagal nerve pathways involved in emesis, demonstrated by first-time direct recording of vagal activation by motilin.

Epidemiological evidence in forensic pharmacovigilance.

Until recently epidemiological evidence was not regarded as helpful in determining cause and effect. It generated associations that then had to be explained in terms of bio-mechanisms and applied to individual patients. A series of legal cases surrounding possible birth defects triggered by doxylamine (Bendectin) and connective tissue disorders linked to breast implants made it clear that in some instances epidemiological evidence might have a more important role, but the pendulum swung too far so that epidemiological evidence has in recent decades been given an unwarranted primacy, partly perhaps because it suits the interests of certain stakeholders. Older and more recent epidemiological studies on doxylamine and other antihistamines are reviewed to bring out the ambiguities and pitfalls of an undue reliance on epidemiological studies.

Evaluation of teratogenic effects of risperidone following simultaneous administration with antihypertensive and antiemetic drugs.

Multiple drug administration is an important aspect of clinical practice particularly in specific physiological situation such as in neonates, elderly or pregnancy, since in all such situations, possibility of unwanted effects increases due to altered body physiology. In present study, the teratogenic effects of multiple drug administration risperidone, meclizine/pyridoxine and hydralazine have been compared with the teratogenic effects of individual drugs in pregnant mice. Moreover the role of folic acid and α-tocopherol if any had also been investigated in reducing the teratogenic effects of these drugs in combinations.

E-cadherin and caveolin-1 alterations in the heart of rats having undergone chlorpromazine-induced toxicity.

Heart damage induced by chlorpromazine (CPZ) toxicity is associated with changes in the expression of various enzymes and proteins. This study aimed to investigate CPZ­induced alterations in cardiac E-cadherin and caveolin-1 (cav-1) after CPZ administration. Male Wistar rats were randomly divided into two groups: a control group and a CPZ group. The CPZ group was administered CPZ intraperitoneally at a single dose of 10 mg/kg for 21 days; the controls were given the same amount of saline via the same route. On Day 22, the rats were anesthetized, and a thoracotomy was performed in all animals. Immunohistochemical analysis was performed to evaluate protein expression of E-cadherin and cav-1. Sections were analyzed by digital image analysis. Results of the present study revealed that cardiac protein expression of E-cadherin and cav-1 was altered after CPZ-induced toxicity in the rat. The expression of E-cadherin was significantly reduced, while expression of cav-1 was significantly increased after CPZ treatment, as supported by integrated optical density analysis, compared with the control (P<0.05). The current findings indicate that such changes in the expression of E-cadherin and cav-1 may be reflected in abnormal cardiac function, and these proteins may be useful in revealing the mechanisms underlying CPZ-induced toxicity and may also provide additional insight for further research.

Casopitant, a neurokinin-1 receptor antagonist with anti-emetic and anti-nausea activities.

Casopitant, an inhibitor of the neurokinin-1 receptor, and its mesylate salt, are being developed by GlaxoSmithKline plc for the potential treatment of chemotherapy-induced nausea and vomiting (CINV), post-operative nausea and vomiting (PONV), as well as for anxiety, depression and insomnia. Phase II trials are ongoing for anxiety, depression and insomnia, and further results are awaited from phase III trials of CINV and PONV. At the time of publication, it was expected that applications to the FDA for regulatory approval for CINV and PONV would be filed in 2008. Casopitant was previously being developed for the treatment of overactive bladder; however, in September 2007, this indication was no longer listed on the company's product pipeline.

Comparison of the effects of metoclopramide and domperidone on HERG channels.

Torsades de pointes (TdP) is a potentially fatal form of ventricular arrhythmia that occurs under conditions where cardiac repolarization is delayed (as indicated by prolonged QT intervals from electrocardiographic recordings). A likely mechanism for QT prolongation and TdP is blockade of the rapid component of the cardiac delayed rectifier K(+) current (I(Kr)), which is encoded by HERG (human ether-a-go-go-related gene). The gastroprokinetic agent cisapride is a potent blocker of HERG currents and serious cardiac arrhythmias and deaths from TdP and ventricular fibrillation have been reported in patients taking cisapride. The aim of the present study was to compare the effects of the gastroprokinetic agents domperidone and metoclopramide on HERG channels transiently expressed in human embryonic kidney (HEK 293) cells using the whole-cell configuration of the patch-clamp technique. Both domperidone and metoclopramide concentration-dependently blocked HERG currents, and the following values were calculated for IC(50) (the concentrations causing half-maximal inhibition) and n (the Hill coefficient): 57.0 nmol/l and 0.99 for domperidone, 5.4 micromol/l and 0.95 for metoclopramide. The observation that the extent of block of HERG currents by domperidone increased at more positive membrane potentials whereas block of HERG currents by metoclopramide displayed a smaller degree of voltage dependency seems to indicate that domperidone and metoclopramide have distinct binding sites on HERG channels. In conclusion, the potency for block of HERG currents is about 100-fold lower for metoclopramide when compared to domperidone.

BNP-7787 (BioNumerik/Baxter Oncology/Grelan).

BioNumerik Pharmacology Inc, Baxter Oncology GmbH (formerly ASTA Medica AG) and Grelan Pharmaceutical Co Ltd are developing BNP-7787 for the potential reduction of toxicity associated with cisplatin and carboplatin treatment in cancer patients.