Correlation of anti-emetic efficacy and plasma levels of ondansetron

Optimizing a therapy for opiate use disorders: Characterizing ondansetron pharmacokinetics in blood and brain

Administration of a widely used 5-hydroxytryptamine receptor (5HT_3A R) antagonist (ondansetron) potently inhibited the development of experimentally induced opioid dependence and withdrawal responses in mice and humans. However, in several studies examining withdrawal symptoms in subjects with chronic opioid use disorders (OUDs), ondansetron exhibited reduced or absent efficacy. Because attenuation of opioid withdrawal symptomatology is mediated within the brain, this study examined single-dose ondansetron pharmacokinetics in the blood and brain of mice. We demonstrate that ondansetron concentrations in the brain (C_brain ng/mg) are 1000-fold lower than the blood concentrations (C_blood ng/ml) and decrease rapidly after ondansetron administration; and that a large percentage of brain ondansetron remains in the ventricular fluid. These results indicate that the ondansetron dose, and the time window between ondansetron and opioid administration, and when withdrawal is assessed are critical considerations for clinical studies involving subjects with chronic OUD. The pharmacokinetic results and the dosing considerations discussed here can be used to improve the design of subsequent clinical trials, which will test whether a more prolonged period of ondansetron administration can provide a desperately needed therapy that can prevent the development of neonatal opioid withdrawal syndrome in babies born to mothers with chronic OUD.

Antiemetics of the 5-hydroxytryptamine 3A antagonist class inhibit muscle nicotinic acetylcholine receptors

Antagonists of the serotonergic 5-hydroxytryptamine 3A receptor (5-HT(3A)R) and muscle nicotinic acetylcholine receptors (nAChR) are widely used in anesthesia practice. Both 5-HT(3A)R and nAChR are ligand-gated ion channels with known pharmacological overlap between some of their agonists and antagonists. We studied the actions of clinically used 5-HT(3A)R antagonist antiemetics and nondepolarizing muscle blockers on ionic currents elicited by the activation of mammalian 5-HT(3A)R and muscle nAChR, expressed in Xenopus laevis oocytes. Currents were recorded using a whole-cell two-electrode voltage clamp technique. Dolasetron, ondansetron, and granisetron reversibly inhibited 5-HT(3A)R function at nanomolar concentrations with 50% inhibitory concentrations (IC(50)) of 11.8, 6.4, and 0.2 nM; the rank order of inhibition correlated well with their clinical antiemetic potencies. The principal metabolite of dolasetron, hydrodolasetron, was 40 times more potent than the parent compound on 5-HT(3A)R (IC(50) = 0.29 nM). The potency of the nondepolarizing muscle blocker d-tubocurarine in blocking 5-HT(3A)R was similar to that of the antiemetics and significantly more than vecuronium and rapacuronium (IC(50) = 11.4 nM, 18.9 microM, 60.5 microM). Conversely, ondansetron, dolasetron, and granisetron also reversibly inhibited nAChR currents in a dose-dependent manner with IC(50)s of 14.2, 7.8, and 4.4 microM for the adult nAChR and 16.0, 18.6, and 13.9 microM for the embryonic nAChR. Again, hydrodolasetron showed significantly (10 times) more inhibitory potency on the adult nAChR than the parent compound dolasetron. These results indicate that drugs that target specific ligand-gated ion channels may also affect other ion channel types.

Options for the prevention and management of acute chemotherapy-induced nausea and vomiting in children

The current standard of care with respect to preventing acute chemotherapy-induced nausea and vomiting (CINV) in children includes the administration of a 5-HT(3) antagonist with or without a corticosteroid, depending on the emetogenicity of the chemotherapy to be given. Problems in assessing the emetogenicity of chemotherapy regimens and nausea severity in children may influence the degree of success of CINV prophylaxis. Nevertheless, the majority of children who receive chemotherapy today experience moderate to complete control of acute CINV when given appropriate antiemetic prophylaxis. If children vomit or experience nausea despite appropriate prophylaxis, then measures must be taken to treat these symptoms since these children are likely to go on to experience delayed or anticipatory CINV. However, appropriate selection of interventions to treat acute CINV in children is limited by the lack of rigorous evidence to support one approach over another. Lorazepam is suggested as an immediate agent for the treatment of acute CINV. Doses and frequencies of the 5-HT(3) antagonist and corticosteroid administered for initial prophylaxis should also be maximized. Further treatment must be tailored to the circumstances and preferences of each child and family. Options include crossover to another 5-HT(3) antagonist, or administration of an adjunctive antiemetic such as metopimazine, low dose metoclopramide, domperidone, alizapride, nabilone, scopolamine, prochlorperazine, or chlorpromazine. Complementary interventions such as acupuncture, hypnosis, counseling, or ginger may also be of benefit. Further study is required to establish optimal antiemetic strategies in children.

Benefits and risks of newer treatments for chemotherapy-induced and postoperative nausea and vomiting

Nausea and vomiting are common adverse effects of chemotherapy, radiation therapy, anaesthesia and surgery. The incidence of chemotherapy-induced nausea and vomiting (CINV) is estimated to vary from 30 to 90%, depending on the type of chemotherapeutic agent used. Radiation-induced emesis varies with anatomical site radiated but is estimated to have an overall incidence of approximately 40%. The incidence of postoperative nausea and vomiting (PONV) depends on the type of anaesthesia and surgery, but overall is estimated to be 20-30%. Evidence-based medicine and meta-analysis have been used to direct medical therapy to help determine equivalence, optimal dose, timing, safety and efficacy of antiemetic medications. Concepts such as the number needed to treat and number needed to harm are helpful to guide the clinician regarding the benefits and risks of a particular treatment. The serotonin 5-HT(3) receptor antagonists ondansetron, granisetron, tropisetron and dolasetron have been important additions to the antiemetic armamentarium. The 5-HT(3) receptor antagonists are similar in chemical structure, efficacy and adverse effect profile. They appear to have no important differences among themselves in clinical outcomes for CINV and PONV. Headache, dizziness, constipation and diarrhoea are their most common adverse effects, and when they occur they are usually mild and easily managed. Haemodynamic changes and extrapyramidal adverse effects are uncommon. ECG changes such as prolonged corrected QT (QTc) interval are infrequent, dose-related and overall judged to be clinically insignificant. As most studies with the 5-HT(3) antagonists have been conducted on relatively healthy patients, caution should be exercised when these drugs are used in susceptible patients with co-morbidities. The clinician must weigh the benefit of administering an antiemetic for CINV or PONV against the risk of occurrence of an adverse event.

Single 8 mg dose of oral ondansetron failed to prevent FAC chemotherapy-induced acute nausea and vomiting

The aim of this open, nonrandomized, monocentric study was to evaluate the efficacy of a single daily dose of 8 mg oral ondansetron in the prophylaxis of acute nausea and vomiting in chemotherapy-naive breast cancer patients receiving their first cycle of chemotherapy with 5-fluorouracil, doxorubicin and cyclophosphamide (FAC). Forty-five female patients were recruited, median age 42 years. The number of emetic episodes and the grade of nausea were recorded. 51% of patients achieved complete, and 9% major control of acute emesis. 33% of patients experienced no acute nausea, and in 18% nausea was mild. Complete protection from nausea and vomiting (complete prophylaxis) was obtained in 12/45 (27%) of patients. Treatment success (no vomiting with no more than mild nausea) was achieved in 18/45 (40%) of patients. We conclude that the efficacy of a single dose of 8 mg oral ondansetron in controlling acute nausea and vomiting induced by FAC chemotherapy is not high enough to justify its use as a sole antiemetic agent in outpatients.

Clinical pharmacokinetics of ondansetron. A review

5-HT3 receptors are ubiquitous in the enteric, sympathetic, parasympathetic and sensory nervous systems and in the central nervous system (CNS) (Kilpatrick et al 1990). In man 5-HT3 receptors are mainly situated on enterochromaffin cells in the gastrointestinal mucosa, which are innervated by vagal afferents (Reynolds et al 1989), and the area postrema of the brain stem, which forms the chemoreceptor trigger zone. Ondansetron is a selective antagonist at 5-HT3 receptors. It is 100 times more potent than metoclopramide at this site (Tyers 1992). It shows limited binding to other receptors and has a wide therapeutic window. Ondansetron is a useful antiemetic which probably has both central and peripheral actions in patients undergoing radiotherapy, cytotoxic chemotherapy or general anaesthesia (Naylor & Rudd 1992). This paper reviews the pharmacokinetics of ondansetron in health and disease to provide information for clinicians; it might alter prescribing and alert them to possible drug interactions.

Oral granisetron with or without methylprednisolone versus metoclopramide plus methylprednisolone in the management of delayed nausea and vomiting induced by cisplatin-based chemotherapy. A prospective randomized trial

BACKGROUND

A single-institution, randomized open trial was prospectively performed to compare orally administered granisetron with or without intramuscularly administered methylprednisolone to metoclopramide plus methylprednisolone in the prevention of delayed nausea and vomiting induced by cisplatin-based chemotherapy. The effects of antiemetic treatments were evaluated from days 2 to 5 of the first cycle after cisplatin administration among patients who had never before received chemotherapy.

METHODS

All patients were treated with chemotherapeutic regimens containing cisplatin greater than or equal to 80 mg/m2 and received antiemetic therapy with granisetron 3 mg intravenously for the control of acute emesis. Patients who responded to treatment during the first 24 hours were randomized to receive (1) metoclopramide (0.5 mg/kg) intramuscularly three times daily plus methylprednisolone (125 mg) intramuscularly once a day or (2) granisetron (1 mg) orally twice daily or (3) oral granisetron (1 mg) orally plus methylprednisolone (125 mg) intramuscularly from days 2 to 5.

RESULTS

Of the patients treated with metoclopramide plus methylprednisolone (n = 92), 53% had complete protection from delayed emesis, 16% a major response, 15% a minor response, and 15% no response. Of the patients treated with granisetron alone (n = 84), 33% had a complete response, 21% a major response, 23% a minor response, and 21% no response. In the patients treated with orally administered granisetron plus intramuscularly administered methylprednisolone (n = 86), 47% had a complete response, 17% a major response, 23% a minor response, and 13% no response. These differences reached statistical significance only when the complete response rate achieved in the metoclopramide plus methylprednisolone group was compared with that recorded in the oral granisetron group (P = 0.012). Moreover, the metoclopramide plus methylprednisolone and the orally administered granisetron plus corticosteroid arms were superior to the orally administered granisetron alone arm in preventing nausea (P < 0.038 and P < 0.002, respectively). No extrapyramidal side effects were noted for the granisetron alone and the granisetron plus methylprednisolone arms, whereas 6% of patients treated with metoclopramide had extrapyramidal adverse effects. Headache was recorded in 8% of patients treated with granisetron alone, in 9% treated with granisetron plus methylprednisolone, and in 3% treated with metoclopramide plus methylprednisolone.

CONCLUSIONS

These data suggest that orally administered granisetron with or without methylprednisolone may be given safely to patients with cancer as prophylactic therapy against delayed emesis after high dose cisplatin therapy. Orally administered granisetron alone was less active than a standard combination of metoclopramide plus methylprednisolone. However, the addition of corticosteroid to orally administered granisetron improved the control of delayed emesis. The efficacy of the combination of metoclopramide plus methylprednisolone and oral granisetron with or without methylprednisolone against delayed emesis still is not entirely satisfactory.

Serotonin receptors: subtypes, functional responses and therapeutic relevance

Recent, rapid progress in the molecular biology of serotonin (5-HT) receptors requires conceptual re-thinking with respect to receptor classification. Thus, based on operational criteria (agonist and antagonist rank order), as well as transduction mechanisms involved and the structure of the receptor protein, the Nomenclature Committee of the Serotonin Club has proposed the following classification and nomenclature: the main receptor types 5-HT1 to 5-HT4, recombinant receptors (e.g. 5-ht5 to 5-ht7) and 'orphan' receptors. The aim of the present review is to discuss the events leading to this classification, the criteria for and functional responses mediated by various 5-HT receptors, as well as the therapeutic possibilities with 5-HT ligands.

Prevention of emesis after strabismus repair in children: a prospective, double-blinded, randomized comparison of droperidol versus ondansetron

STUDY OBJECTIVE

To compare the effectiveness of ondansetron with droperidol in preventing postoperative emesis in children after strabismus repair.

DESIGN

Randomized, double-blind study.

PATIENTS AND SETTING

57 ASA physical status I and II children aged 3 to 14 years, undergoing outpatient strabismus repair in two separate study centers.

INTERVENTIONS

Patients were randomized to receive either 0.15 mg/kg intravenous (i.v.) ondansetron or 0.075 mg/kg i.v. droperidol shortly after induction of anesthesia.

MEASUREMENTS AND MAIN RESULTS

Number of episodes of emesis and times to discharge from the recovery room and ambulatory center were assessed. Twenty-nine (94%) of 31 children who received ondansetron and 21 (81%) of 26 children who received droperidol were emesis-free (p = NS). There were no significant differences in the number of episodes of emesis on the day after surgery or times to discharge.

CONCLUSIONS

Ondansetron is at least as effective as droperidol in reducing the frequency of emesis in children after strabismus repair, and it did not shorten times to discharge home. The low number of patients in our study may have masked a difference in effect between the two groups. The clinician should decide whether the increased cost of ondansetron justifies its use over other antiemetics.

An open study to assess the safety, tolerance and pharmacokinetics of an intravenous infusion of granisetron given at 3 mg over 30 s in patients receiving chemotherapy for malignant disease

Granisetron is a highly potent and selective 5-hydroxytryptamine3 (5-HT3) receptor antagonist indicated for the prevention of cytotoxic-induced nausea and vomiting. Clinical trials have demonstrated granisetron to be effective and well tolerated at a standard dose of 40 micrograms/kg or 3 mg given i.v. as a 5-min infusion. In this study, the efficacy and safety of granisetron given as a 30-s infusion was assessed. A total of 21 patients, scheduled to undergo chemotherapy, received a single 3-mg i.v. dose of granisetron over 30 s, completed at 1 h before chemotherapy administration. Patients were allowed two further i.v. doses of granisetron at 3 mg within the 24-h assessment period. Changes from baseline values in vital signs were analysed prior to granisetron administration and at 30 s as well as 1, 10, 15, 30 and 60 min after granisetron administration. Holter ECG recordings were taken for 6 h prior to and 1 h after administration. No significant change was found in vital signs at 30 s or 1 min after granisetron infusion. There was a small but statistically significant fall in diastolic blood pressure as compared with baseline and a non-significant trend in favour of a reduction in heart rate at 10 and 15 min. No ECG abnormality was recorded post-infusion that had not been present pre-infusion. None of these changes was considered to be clinically relevant. The treatment was well tolerated. The most frequently reported adverse events were constipation (n = 6) and headache (n = 5). Maximal plasma levels of granisetron were within the range of 44.57-410 ng/ml except in one patient. The median values recorded for peak concentration (Cmax) and area under the curve (AUC) were 195 ng/ml and 71.2 ng h ml-1, respectively. In conclusion, granisetron at 3 mg was shown to be safe and well tolerated when given as a 30-s i.v. infusion to patients receiving chemotherapy for malignant disease.

Ondansetron versus granisetron in the prevention of chemotherapy-induced nausea and vomiting. Results of a prospective randomized trial

BACKGROUND

A single-institution, prospective, randomized open trial was performed to compare ondansetron and granisetron in the prevention of chemotherapy-related nausea and vomiting. The effect of antemetic drugs was analyzed indipendently for patients treated with highly emetogenic chemotherapy (Study 1), and those treated with moderately emetogenic regimens (Study 2).

METHODS

In Study 1, 182 patients treated with chemotherapeutic regimens containing high dose cisplatin (more than 70 mg/m2) were randomized to receive 24 mg of ondasentron intravenously (i.v.) or 3 mg of granisetron i.v. for the control of acute emesis. Patients treated with fractionated chemotherapy and those followed-up for delayed emesis also received 8 mg of ondansetron orally twice a day or 3 mg of granisetron i.v. on the days after Day 1. In Study 2, 164 patients were randomized to receive either 16 mg of ondansetron i.v. or 3 mg of granisetron i.v. to prevent emesis in the first 24 hours.

RESULTS

In the ondansetron group in Study 1, a complete response (CR) (i.e., no vomiting, nausea possible) from acute emesis was achieved in 52% of cases, a major response (MR) in 29%, and a minor response (MiR) in 14%. In the granisetron group in Study 1, a CR was seen in 49% of patients, an MR in 24%, and an MiR in 12%. Failure was recorded in 5% and 15% of cases in the ondansetron and granisetron groups, respectively. No statistically significant difference in any response category was seen between the two groups. In the ondansetron group, a complete protection from delayed emesis was recorded in 39% of cases, an MR in 32%, an MiR in 21%, and failure in 16%. In the granisetron arm, 36% of the patients had a CR, 22% had an MR, 14% had an MiR, and 14% experienced treatment failure. Again, these differences did not reach statistical significance. In Study 2, no statistical significant difference was observed between the ondansetron arm and the granisetron arm, both for acute and delayed emesis. Both ondansetron and granisetron were tolerated very well by most patients, with no severe side effects. In the group of patients treated with ondansetron, however, the incidence of headache (9%) was higher than in the group treated with granisetron (4%).

CONCLUSIONS

These data suggest that although both ondansetron and granisetron are very effective drugs for the control of acute emesis, their efficacy against delayed emesis is still not entirely satisfactory.

Are all 5-HT3 receptor antagonists the same?

A number of 5-HT3 receptor antagonists are currently in clinical development as antiemetics. In this paper we focus on two of these antagonists, granisetron and ondansetron, and compare their antimetic activity against cisplatin (10 mg/kg i.v.)- or whole body X-irradiation (200 rads)-induced emesis in the conscious ferret. The results presented here have been discussed in the light of the recently published literature. Our data suggest that in comparison to ondansetron, granisetron is a more potent, longer acting and pharmacologically "cleaner" compound with a more conventional dose-response profile. The possible impact of these features upon the performance of these compounds in the clinic is discussed particularly with respect to dosing regimens and clinical efficacy. Differences appear to be emerging between granisetron and ondansetron in both these respects, although a direct head-to-head clinical comparison has yet to be carried out. This would involve studies monitoring a sufficiently high number of patients receiving severely emetogenic regimes to allow real clinical differences to be detected with the appropriate statistical power.

5-HT3 receptor antagonists. An overview of their present status and future potential in cancer therapy-induced emesis

The serotonin (5-hydroxytryptamine, 5-HT) antagonists, which bind at the type 3 receptor (5-HT3 receptor), have been evaluated in several preclinical models and found to be effective in alleviating cancer therapy-related emesis. The antiemetic efficacy of ondansetron (GRF-38032F, odanserin), granisetron (BRL-43694), tropisetron (ICS-205930), MDL-72222 and MDL-73147EF, batanopride (BMY-25801-01) and several others is at various stages of investigation. Ondansetron is currently marketed in several countries and the same will soon be true for granisetron. At this stage it is not yet possible to evaluate the comparative efficacy of each of these compounds, although recent preclinical data reveal some differences in the affinity of these compounds, for other receptors. Side effects related to these agents have been minor, consisting mainly of slight headaches; possible rises in liver enzymes related to some compounds need further evaluation. Future studies will need to determine the exact role of 5-HT3 antagonists, although their cost may confine their use to patients at high risk for side effects from metoclopramide.

Ondansetron. Therapeutic use as an antiemetic

Ondansetron (GR 38032F) is a highly selective 5-HT3 receptor antagonist, one of a new class of compounds which may have several therapeutic applications. Animal and clinical studies show that ondansetron reduces the 24-hour incidence and severity of nausea and vomiting induced by cytotoxic drugs, including cisplatin, and by single exposure, high dose radiation. Ondansetron is more effective than high dose metoclopramide in the 24 hours following chemotherapy, and preliminary clinical evidence suggests that it is equally effective in the following 4 days. It is also more effective than the 'moderate' doses of metoclopramide used to suppress emesis following radiotherapy. The antiemetic efficacy of ondansetron is enhanced by dexamethasone in cisplatin-treated patients. Importantly, extrapyramidal effects have not been reported with ondansetron. Further comparisons are required with standard combination antiemetic therapy to complement the data presently available. Thus, ondansetron is a promising new agent for prophylaxis against nausea and vomiting in chemotherapy and radiotherapy. It may be particularly useful in young and elderly patients who are more susceptible to extrapyramidal symptoms induced by high dose metoclopramide. With its improved tolerability and clinical response profiles, ondansetron represents an important advance in a difficult area of therapeutics.