Comparative efficacy of a single oral dose of ondansetron and of buspirone against cisplatin-induced emesis in cancer patients

Looking beyond 5-HT(3) receptors: a review of the wider role of serotonin in the pharmacology of nausea and vomiting

The concept that 5-hydroxytryptamine (5-HT; serotonin) is involved in the emetic reflex was revealed using drugs that interfere with its synthesis, storage, release and metabolism ahead of the discovery of selective tools to modulate specific subtypes of receptors. This review comprehensively examines the fundamental role of serotonin in emesis control and highlights data indicating association of 5-HT1-4 receptors in the emetic reflex, whilst leaving open the possibility that 5-HT5-7 receptors may also be involved. The fact that each receptor subtype may mediate both emetic and anti-emetic effects is discussed in detail for the first time. These discussions are made in light of known species differences in emesis control, which has sometimes affected the perception of the translational value of data in regard to the development of novel anti-emetic for use in man.

Intravenous buspirone for the prevention of postoperative nausea and vomiting

RATIONALE

Buspirone, a partial 5HT(1A) agonist and D₂ and D₃ antagonist, has shown promising antiemetic efficacy when given parenterally in animal models, but its efficacy for the prevention of postoperative nausea and vomiting (PONV) is unknown.

OBJECTIVE

To study the efficacy and dose-responsiveness of intravenous buspirone for the prevention of PONV.

METHODS

A randomised, double-blind, placebo-controlled study was performed in adults at moderate to high PONV risk undergoing surgery with a general anaesthetic. Patients were randomised to receive an intravenous dose of buspirone (0.3, 1.0, 2.0, 3.0 mg) or placebo at the end of surgery. The primary endpoint was the cumulative 24-h PONV incidence (i.e. any nausea and/or vomiting). Vomiting included retching. Nausea was defined as a score of ≥ 4 on an 11-point verbal rating scale running from zero (no nausea) to ten (the worst nausea imaginable).

RESULTS

A total of 257 patients received the study drug and fulfilled the criteria for inclusion in the primary efficacy and safety analyses. With placebo, the mean 24-h PONV incidence was 49.0 % (90 % confidence interval [CI] 37.5-60.5 %). With buspirone, that incidence ranged from a mean of 40.8 % (29.3-52.4 %) in the 1 mg arm to 58.0 % (46.5-69.5 %) in the 0.3 mg arm (P > 0.05 for all comparisons). There was no difference between placebo and buspirone at any dose for any other efficacy endpoint, nor in the number or severity of adverse events or any other safety measures.

CONCLUSION

We were unable to show that intravenous single-dose buspirone, at the tested dose-range, was effective at preventing PONV in surgical adult patients. The present study emphasises the difficulty in extrapolating from animal models of emesis to clinical efficacy in PONV.

Serotonin pharmacology in the gastrointestinal tract: a review

Serotonin (5-hydroxytryptamine or 5-HT) plays a critical physiological role in the regulation of gastrointestinal (GI) function. 5-HT dysfunction may also be involved in the pathophysiology of a number of functional GI disorders, such as chronic constipation, irritable bowel syndrome and functional dyspepsia. This article describes the role of 5-HT in the enteric nervous system (ENS) of the mammalian GI tract and the receptors with which it interacts. Existing serotonergic therapies that have proven effective in the treatment of GI functional disorders and the potential of drugs currently in development are also highlighted. Advances in our understanding of the physiological and pathophysiological roles of 5-HT in the ENS and the identification of selective receptor ligands bodes well for the future development of more efficacious therapies for patients with functional GI disorders.

The Partial 5-Hydroxytryptamine1A Receptor Agonist Buspirone does not Antagonize Morphine-induced Respiratory Depression in Humans

Based on experiments in rats, serotonin receptor 5-hydroxytryptamine (5-HT)(1A) agonists have been proposed as a potential therapeutic strategy for the selective treatment of opioid-induced respiratory depression. We investigated the clinical applicability of this principle in healthy volunteers. Twelve subjects received 0.43 mg/kg morphine (30 mg for 70 kg body weight) administered intravenously (i.v.) over approximately 2 h. At the start of the morphine infusion, they received in a randomized, double-blind cross-over design 60 mg p.o. buspirone or placebo. Respiratory depression (hypercapnic challenge) and pain (electrical stimuli: 5 Hz sinus 0-20 mA; chemical stimuli: 200 ms gaseous CO(2) pulses applied to the nasal mucosa) were assessed at baseline, at the end of the morphine infusion, and a third time after antagonizing the opioid effects by i.v. administration of 2 mg naloxone. The linear relationship between the minute ventilation and the CO(2) concentration in the inspired air of 1.07+/-0.27 l/mm Hg CO(2) at baseline conditions became shallower (0.45+/-0.23 l/mm Hg CO(2)) after morphine administration (P<0.001), indicating respiratory depression, which was significantly reversed by naloxone (0.95+/-0.43 l/mm Hg CO(2); P=0.001). Co-administration of buspirone had no effect on morphine-induced respiratory depression (slope 0.45+/-0.23 l/mm Hg CO(2) under morphine plus placebo versus 0.38+/-0.25 l/mm Hg CO(2) under morphine plus buspirone; P=0.7). Significant morphine-induced analgesia was observed in both pain models and was reversed by naloxone but unaffected by buspirone. Buspirone significantly increased the nausea induced by morphine (P=0.011). Oral co-administration of a high dose of the clinically available 5-HT(1A) agonist buspirone cannot be advised as a remedy for opioid-induced respiratory depression. This is indicated by its lack of anti-respiratory depressive effects and by the buspirone-associated increase of morphine-induced nausea.

Treatment of nausea and vomiting: gaps in our knowledge

The past 20 years have seen notable advances in our understanding of the physiology and pharmacology of the emetic reflex leading to the identification of the anti-emetic effects of 5-hydroxytryptamine(3) (5-HT(3)) and neurokinin(1) receptor (NK(1)) antagonists. The introduction of 5-HT(3) and NK(1) receptor antagonists into the clinic has had a major impact in alleviating the nausea and vomiting associated with the treatment of cancer and the sequelae to anaesthesia and surgery (post-operative nausea and vomiting, PONV). Despite these advances there are major gaps in our understanding. Interestingly, one of these is the relatively poor ability to treat nausea. Additional gaps in our knowledge are highlighted to provide a framework within which directions for research can be proposed. Particular attention is drawn to: lacunae in knowledge of some currently used anti-emetics such as the source of dopamine required to initiate emesis; the theoretical assumptions and mechanisms underlying the concept of a "universal anti-emetic"; the variety of receptors at which agonists act to have anti-emetic effects (GABA (B), CB(1), 5-HT(1A), ghrelin, opioid); issues of translation from animals to humans and the relationship between the pathways involved in emesis and certain gastrointestinal disorders such as dyspepsia and gastroesophageal reflux, with the latter being of particular interest as some agents affecting reflux are also anti-emetic. Together, the unmet clinical need to adequately control nausea, possibly by new drugs acting within the brainstem, and the significant gaps in understanding key aspects of the emetic reflex, suggest an important need to focus and re-direct research into the distressing and sometimes life-threatening symptoms of nausea and vomiting.

Randomized, multicenter comparison of oral granisetron and oral ondansetron for emetogenic chemotherapy

STUDY OBJECTIVES

To compare the antiemetic effectiveness and safety of oral granisetron plus dexamethasone with those of oral ondansetron plus dexamethasone administered before emetogenic chemotherapy.

DESIGN

Randomized, prospective, multicenter, open-label study.

SETTINGS

University-teaching hospital and veterans health care system.

PATIENTS

Sixty-one chemotherapy-naïve patients scheduled to receive emetogenic antineoplastic agents.

INTERVENTION

A single-dose oral granisetron 1 mg and dexamethasone 12 mg or single-dose oral ondansetron 16 mg and dexamethasone 12 mg was administered before chemotherapy.

MEASUREMENTS AND RESULTS

Twenty-four hours after administration patients were contacted to assess nausea, emesis, and adverse events. There were no statistical differences in frequency of nausea or emesis between groups. Seventy-six percent and 82% of patients receiving ondansetron and granisetron, respectively, experienced no emesis 24 hours after chemotherapy. Complete protection from nausea occurred in 58% and 46% of patients receiving the drugs, respectively. Adverse events were similar between groups.

CONCLUSION

Oral granisetron 1 mg and ondansetron 16 mg plus dexamethasone are safe and effective in preventing nausea and vomiting related to emetogenic chemotherapy.