L-683,877: Pharmacological profile of a novel 5-HT3 receptor antagonist

Cisplatin-induced emesis: systematic review and meta-analysis of the ferret model and the effects of 5-HT₃ receptor antagonists

Purpose

The ferret cisplatin emesis model has been used for ~30 years and enabled identification of clinically used anti-emetics. We provide an objective assessment of this model including efficacy of 5-HT₃ receptor antagonists to assess its translational validity.

Methods

A systematic review identified available evidence and was used to perform meta-analyses.

Results

Of 182 potentially relevant publications, 115 reported cisplatin-induced emesis in ferrets and 68 were included in the analysis. The majority (n = 53) used a 10 mg kg⁻¹ dose to induce acute emesis, which peaked after 2 h. More recent studies (n = 11) also used 5 mg kg⁻¹, which induced a biphasic response peaking at 12 h and 48 h. Overall, 5-HT₃ receptor antagonists reduced cisplatin (5 mg kg⁻¹) emesis by 68% (45–91%) during the acute phase (day 1) and by 67% (48–86%) and 53% (38–68%, all P < 0.001), during the delayed phase (days 2, 3). In an analysis focused on the acute phase, the efficacy of ondansetron was dependent on the dosage and observation period but not on the dose of cisplatin.

Conclusion

Our analysis enabled novel findings to be extracted from the literature including factors which may impact on the applicability of preclinical results to humans. It reveals that the efficacy of ondansetron is similar against low and high doses of cisplatin. Additionally, we showed that 5-HT₃ receptor antagonists have a similar efficacy during acute and delayed emesis, which provides a novel insight into the pharmacology of delayed emesis in the ferret.

Selective potentiating effect of RS14203 on a serotoninergic pathway in anesthetized rats

The usefulness of selective inhibitors of type 4 phosphodiesterase (PDE4) in the treatment of inflammation and pulmonary diseases is limited by their side effects: nausea and vomiting. We studied the effect of three structurally diverse PDE4 inhibitors on the vagal nerve afferent and efferent fibers in anesthetized rats. The effects of RS14203, (R)-rolipram, and CT-2450 were evaluated on the von Bezold-Jarisch reflex (vagal afferent fibers) and in a model of vagal electrical stimulation (vagal efferent fibers). All three PDE4 inhibitors were administered at 1, 10, or 100 µg/kg (iv) 15 min prior to the induction of bradycardia by an iv injection of 2-methyl-5-HT (von Bezold-Jarisch reflex) or by vagal electrical stimulation. At 100 µg/kg, RS14203 significantly potentiated the 2-methyl-5-HT response. No statistically significant effects were observed with (R)-rolipram or CT-2450 at the doses studied. RS14203, (R)-rolipram, or CT-2450 (1-100 µg/kg iv) did not affect the bradycardia induced by vagal electrical stimulation. Consequently, our results show that RS14203 selectively facilitates serotoninergic neurotransmission in vagal afferent fibers. The emetic action of RS14203 may be mediated by this mechanism.Key words: PDE4 inhibitors, von Bezold-Jarisch reflex, emesis, vagal afferent and efferent fibres, bradycardia.

Pharmacology of serotonin as related to anesthesia

Serotonin (5-hydroxytryptamine) is an important biogenic amine that fulfills the role of neurotransmitter and neuromodulator. It has been a focus of interest during the last decade. Its diversity of pharmacologic actions is related to a wide variety of receptors and effector mechanisms. Seven serotonin receptor families have been identified thus far. They are genetically different transmembrane proteins composed of several hundred amino acids. The majority of these are G-protein-coupled, except the 5-HT3 receptors, which are directly ligand gated to fast ion channels. Serotonin is widely distributed in the body within the central and peripheral nervous systems, smooth muscles, and platelets, in particular. Consequently, its effects manifest mainly in these organs and influence a wide variety of neural, vascular, smooth muscle, and platelet functions. (Melatonin, a physiologically active metabolite of serotonin, is also instrumental in affecting many neural and hormonal functions.) Several selective agonists and particularly many selective antagonists have been developed for serotonin, which helped the serotonin receptor subtype classification. Some of these drugs are also used therapeutically in the treatment of migraine (eg, sumatriptan, which is a 5-HT1 receptor agonist), vascular disorders (5-HT2 antagonists), and nausea and vomiting (5-HT3 antagonists, eg, dolasetron, granisetron, ondansetron, and tropisetron), and have been investigated in gastrointestinal motility disorders (5-HT4 antagonists) and behavioral psychopathologies (5-HT1 agonists and 5-HT2-4 antagonists). Serotonin reuptake inhibitors are of particular clinical importance in the treatment of psychological illness. Future use of these drugs is also envisioned in the treatment of certain types of pain syndromes. Awareness of the serotonergic drugs and the recognition of possible drug interactions among drugs that influence serotonergic mechanisms in humans are becoming increasingly important in the practice of anesthesiology.