Neurochemical Investigations into the Human Area Postrema

The Benefits of Olanzapine in Palliating Symptoms

OPINION STATEMENT

Olanzapine has become a major drug in the management of chemotherapy-induced nausea and vomiting as a prophylactic agent. In addition, a recent randomized trial has demonstrated its benefits in treating nausea and vomiting associated with advanced cancer. The added benefit to olanzapine is that it also stimulates appetite. As a result, since it treats multiple symptoms associated with advanced cancer, it is likely to become the antiemetic of choice in palliative care at least in the USA. The added benefit of treating insomnia and the avoidance of benzodiazepines should place olanzapine in at the top of the list of drugs to use for patients who do complain of insomnia. There is no good evidence that it potentiates the respiratory depression of opioids unlike benzodiazepines. The evidence is weak that olanzapine in as an adjuvant analgesic. Hopefully, future trials will explore this in greater depth. The benefits of adding olanzapine to potent opioids are that it may reduce craving, drug cues, and opioid misuse. Other symptoms like anxiety and depression may be addressed by the addition of olanzapine to standard antidepressants.

Long-Term Safety and Clinical Effectiveness of Controlled-Release Metoclopramide in Cancer-Associated Dyspepsia Syndrome: A Multicentre Evaluation

Patients with cancer frequently report gastrointestinal symptoms such as anorexia, early satiety, nausea, vomiting, and bloating. A reduction of the severity of some of these symptoms would benefit the patient by enhancing quality of life and improving their treatment. Forty-eight patients (25 female and 23 male; mean age 63 ±11 years) with a minimum two-week history of cancer-associated gastrointestinal symptoms were assigned to a single, open-label treatment group and received controlled-release metoclopramide 20 mg–80 mg q12h for a maximum period of 12 weeks (mean 46 ±35 days). There was a 40%-60% decrease in the severity of nausea over the first two weeks of treatment, and an approximate 50% reduction in severity of vomiting over the first four weeks of treatment. Appetite and bloating also improved, although smaller and less consistent changes were observed. Patient ratings of overall clinical effectiveness with respect to relief from symptoms and tolerability of side effects indicated that controlled-release metoclopramide was highly and moderately effective in 36% and 30% of the patients, respectively. Controlled-release metoclopramide is a useful treatment for the management of gastrointestinal symptoms associated with the cancer-associated dyspepsia syndrome including nausea, vomiting, loss of appetite, and bloating.

Efficacy of a Scheduled IV Cocktail of Antiemetics for the Palliation of Nausea and Vomiting in a Hospice Population

This is a retrospective analysis of 10 mg metoclopramide, 25 mg diphenhydramine, and 4 mg dexamethasone given intravenous piggyback every 6 hours for nausea or vomiting. Outcome measures were rapidity of symptom relief based on the self-report of the patient and nursing documentation of relief from symptoms of nausea or vomiting. Seven hundred and ninety seven patients were admitted to the inpatient hospice unit during a 2-year period. Sixty-three patients developed nausea or vomiting requiring the cocktail. Fifty-seven patients (90%) had objective response as reflected in nursing notes. Symptom relief was usually noted within 2 days with improvement in oral intake and enjoyment in activities, such as parties and family interactions. Partial relief was noted in patients with gastrointestinal malignancies and peritoneal carcinomatosis even with the addition of other antiemetics to the cocktail.

Subcellular localization of nitric oxide synthase in the cerebral ventricular system, subfornical organ, area postrema, and blood vessels of the rat brain

The distribution of neuronal nitric oxide synthase (nNOS) has been studied in the more rostral portion of the lateral ventricle, subfornical organ, area postrema and blood vessels of the rat central nervous system. nNOS was located by means of a specific polyclonal antibody, by using light and electron microscopy. Light microscopy showed immunoreactive varicose nerve fibers and terminal boutons-like structures in the lateral ventricle, positioned in supra- and subependimal areas. The spatial relationships between immunoreactive neuronal processes and the wall of the intracerebral blood vessels were studied. Electron microscopy showed numerous nerve fibers in the wall of the lateral ventricle; many were nNos-immunoreactive and established very close contact with ependymal cells. Immunoreactive neurons and processes were found in the subependymal plate of the ventricular wall, the subfornical organ, the area postrema, and the circularis nucleus of the hypothalamus. In these last three areas, the immunoreactive neurons were found close to the perivascular space of fenestrated and nonfenestrated blood vessels. The nNOS immunoreactivity was localized to the endoplasmic reticulum, cisterns, ribosomes, neurotubules, and in the inner part of the external membrane. In the terminal boutons, the reaction product was found surrounding the vesicle membranes. This distribution showed nNOS as a predominantly membrane-bound protein. The nitrergic nerve fibers present in the wall of the ventricular system might regulate metabolic functions as well as neurotransmission in the subfornical organ, area postrema and circularis nucleus of the hypothalamus.

Increased incidence of retching and vomiting during periovulatory phase after middle ear surgery

PURPOSE

To assess the effect of the menstrual cycle on postoperative retching and vomiting (R&V) after middle ear surgery, and the efficacy of prophylaxis against R&V in female patients with transdermal scopolamine during either general or local anaesthesia and with intravenous ondansetron during general anaesthesia.

METHOD

A post hoc analysis of the data on 85 female patients with normal menstrual cycles from three prospective studies on the prophylaxis of postoperative nausea and vomiting after middle ear surgery on 205 patients.

RESULTS

Periovulatory period (menstrual dates 11-24) and history of motion sickness were predictors for R&V. During 2-24hr, both the percentage of patients needing droperidol and the mean number of doses were lower in the perimenstrual group (menstrual dates 25-10) than in the periovulatory group 27 vs 51% (P < 0.05) and 0.2 vs 0.7 (P < 0.01), respectively. Prophylaxis with transdermal scopolamine was a predictor for lowered R&V (P < 0.05) and resulted in fewer doses of droperidol (0.4 +/- 0.7 vs 1.4 +/- 1.5, P < 0.01). This reduction was significant during the periovulatory period (from 1.4 +/- 1.3 to 0.3 +/- 0.5, P < 0.005). Ondansetron reduced the mean need for droperidol from 1.4 +/- 1.5 to 0.6 +/- 0.8, (P < 0.05).

CONCLUSION

The incidence of R&V after middle ear surgery was lower during the perimenstrual phase. In the periovulatory phase, transdermal scopolamine was more efficient as prophylaxis against R&V than ondansetron. All female patients scheduled for middle ear surgery should be considered individually to receive prophylaxis against R&V.

Oral administration of NNC 756--a placebo controlled PET study of D1-dopamine receptor occupancy and pharmacodynamics in man

NNC 756 is a new benzazepine with high affinity and selectivity for D1-dopamine receptors. In a double-blind, placebo controlled, cross-over study, positron emission tomography and the radioligand [11C]SCH 23390 were used to determine central D1-dopamine receptor occupancy after a single oral dose of 80 mg NNC 756 in three healthy men. NNC 756 induced 75, 66 and 47% occupancy of D1-dopamine receptors in the putamen of at 1.5 h after drug administration and 46, 36 and 24% after 7.5 h. There was a hyperbolic relationship between the occupancy values and the serum concentrations. The Ki value for the hyperbola was 6.4 ng/ml (+/- SD 1.4). The occupancy at 1.5 h is on the same level as that shown to induce effects in animal models for prediction of antipsychotic effect. Restlessness (akathisia) appeared in two subjects and nausea in one subject at time of peak drug concentration in serum. The oral dose level of 80 mg should be appropriate to investigate the potential antipsychotic effect of NNC 756.

Control of chemotherapy-induced emesis

The development of antiemetic drugs has been one of the most rewarding areas of oncologic research, since therapeutic advances in this area can result in immediate improvement in the quality of life for patients undergoing chemotherapy. Antiemetic therapy has progressed dramatically during the past decade and a half. Fifteen years ago, patients receiving cisplatin for the first time had a median of 12 vomiting episodes within the first 24 hours, whereas now more than 50 percent of such patients have no vomiting episodes at all. Theoretical and clinical challenges remain, however, in the effort to control chemotherapy-induced emesis. The mechanisms of anticipatory vomiting and delayed vomiting are still not understood, and consistently effective therapeutic approaches to these problems have yet to be developed.

Supersensitivity psychosis with concurrent episodic vomiting

A patient with a 15-year history of psychiatric illness treated with neuroleptics presented with vomiting, thought alienation, auditory hallucinations and self-neglect. Dopaminergic supersensitivity was diagnosed and increased doses of neuroleptics caused cessation of vomiting. The patient is currently attempting discontinuation of neuroleptics.

Antiparkinsonian dopamine agonists: a review of the pharmacokinetics and neuropharmacology in animals and humans

With the intention of compensating for the deficit of endogenous dopamine (DA) in the basal ganglia of Parkinsonian patients by substitution with agents which directly stimulate central DA receptors, synthetic DA agonists have been introduced almost 20 years ago for the symptomatic treatment of Parkinson's disease. The original expectation that DA agonists would be able to completely restore extrapyramidal motor function in Parkinsonian patients has turned out as too mechanistic and simplicative. However, undoubtedly DA agonists have improved therapeutic possibilities in Parkinson's disease. Thus, clinical evidence from controlled chronic studies in patients indicates that the therapeutic results following the early application of DA agonists in combination with L-DOPA on a long-term base are superior to the respective monotherapy. However, none of the DA agonists currently employed for antiparkinsonian treatment i.e. apomorphine and the ergoline derivatives bromocriptine, lisuride and pergolide, is optimal with respect to pharmacokinetic properties (poor oral bioavailability with considerable intra- and interindividual variation) or pharmacological profiles (low selectivity for DA receptors in case of the ergot agonists). The pathophysiology underlying Parkinson's disease which turned out more complex than initially expected might provide another explanation for the limited therapeutic potential of DA agonists. Therefore, apart from summarizing the pharmacokinetics, biotransformation, neuropharmacology and neurobiochemistry of the DA agonists employed clinically, the present article also reviews physiological aspects of (a) central dopaminergic neurotransmission including the topographical distribution of DA receptor subtypes and their functional significance, (b) the intracellular signal processing in striatal output neurons and (c) the intraneuronal mechanisms which integrate the various neurotransmitter signals converging on the striatal output neuron to a demand-adjusted effector cell response via the cross-talk between the different second messenger systems. Based on these considerations, potential pharmacological approaches for the development of improved antiparkinsonian drugs are outlined. There is a therapeutic demand for more selective and better bioavailable DA agonists. In particular, selective D-1 receptor agonists are highly desirable to provide a more specific probe than SKF 38 393 for clarifying the current controversy on the disparate findings in nonprimate species and monkeys or Parkinsonian patients, respectively, regarding the functional significance of D-1 receptors for the antiparkinsonian action of DA agonists or L-DOPA. The therapeutic importance of D-2 receptor activation is generally accepted; whether DA agonists combining a balanced affinity to both D-1 and D-2 receptors within one molecule (to some extent a property of apomorphine) might be superior to subtype-specific DA agonists remains to be tested clinically.(ABSTRACT TRUNCATED AT 400 WORDS)

Neuropharmacologic correlates of deglutition: lessons from fictive swallowing

Pharmacologic investigations into the transmission processes underlying fictive swallowing in the rat have disclosed the potential diversity of chemical signals used in central deglutitive pathways. Monoaminergic mechanisms appear to serve as links between subcortical structures and the medullary pattern generator of swallowing (PGS), and may play a critical role in maintaining internal facilitatory drive, required by the PGS for optimal responsivity to peripheral sensory input. Cholinergic bulbar interneurons form an integral component of the PGS subnetwork controlling esophageal peristalsis. Local GABA neurons exert a tonic inhibition of the buccopharyngeal stage, may regulate buccopharyngeal-esophageal coupling, and may contribute to peristaltic rhythmic generation at both the premotoneuronal and motoneuronal level. Receptor subtypes for excitatory amino acids (glutamate, aspartate) are differentially associated with deglutitive premotoneurons for both the buccopharyngeal and esophageal stage, as well as with ambiguus motoneurons. Preliminary evidence suggests the existence of excitatory peptidergic mechanisms involving thyrotropin-releasing hormone, vasopressin, oxytocin, and somatostatin, a probable candidate for excitatory transmitter in the solitarioambigual internuncial projection to motoneurons innervating esophageal striated musculature. Further validation of this experimental model may ultimately help to establish a framework for the clinical recognition, management, and exploitation of drug actions on central deglutitive neuroeffectors.

Pathophysiology of cytotoxic drug-induced emesis: far from crystal-clear

Both radiotherapy and chemotherapy for cancer are capable of causing severe nausea and vomiting, which formerly often interfered with the patient's compliance to treatment. The basic pathway and pharmacological mechanisms involved in this are still poorly understood. The recent discovery, however, that 5-HT3 receptor antagonists can prevent or greatly reduce chemotherapy-induced emesis led to a re-evaluation of the sequence of events occurring in the protective emetic reflex, which are reviewed in this paper. The vomiting centre co-ordinates the incoming and outgoing information, and is thought to be represented by complex interactions between different adjacent areas in the brainstem. Whether the main role in the emetic reflex arch is accomplished by either the central part (chemoreceptor trigger zone) or the peripheral part (gastro-intestinal tract) needs further confirmation A more important role, however, of the vagal nerve and the gastro-intestinal tract is generally accepted. The neurotransmitter serotonin (5-HT) appears to play a major role in chemotherapy-induced emesis via the 5-HT receptor. These indications could form the basis for further investigations into the involvement of other neurotransmitters, and the character of their interactions.

Area postrema: cholinergic and noradrenergic regulation of emesis. A new concept

In unanaesthetized cats the biochemical mechanisms and the functional characteristics of the emetic action of injection of noradrenaline and McN-A-343, a ganglionic muscarinic stimulant into the cerebral ventricle (i.c.v.) through chronically implanted cannulae were investigated. Both produced dose-dependent and shortlasting emetic response. The emesis evoked by noradrenaline was abolished, whereas the emesis induced by McN-A-343 was not completely blocked after ablation of the area postrema. Further, the emetic response to noradrenaline as well as to McN-A-343 was attenuated or blocked in cats pretreated with 6-hydroxydopamine (i.c.v.) and hemicholinium (i.c.v.); it was abolished in cats pretreated with reserpine (i.c.v.). On the other hand, the emetic response to i.c.v. noradrenaline and to i.c.v. McN-A-343 was not virtually altered in cats pretreated with bretylium (i.c.v.), alpha-methyl-p-tyrosine (i.c.v.) and 5,6-dihydroxytryptamine (i.c.v.). It is postulated that noradrenergic neurones as well as cholinergic axon terminals within the area postrema are necessary for the emetic action of noradrenaline, whereas cholinergic axon terminals within the area postrema subserve the emetic response to McN-A-343. A functional link between cholinergic terminals and noradrenergic neurones as well as a modulatory role of noradrenergic afferents on cholinergic afferents mediating emesis within the area postrema is further proposed. Thus, noradrenergic neurones might represent a common site of confluence of different inputs subserving the emesis in the area postrema. Finally, cholinergic terminals sometimes bypass this area and synapse in the emetic regions of the brainstem regulating emesis.