Pizotifen (BC-105): a review of its pharmacological properties and its therapeutic efficacy in vascular headaches

Sustainable, Green, and Sensitive Spectrofluorimetric Approach for Pizotifen Maleate Detection in Tablets and Human Plasma via Photo-Induced Electron Transfer Inhibition

Pizotifen maleate (PZM) is an anti-migraine drug. Effective treatment requires accurate measurement of PZM levels in patients and constant medication concentrations in tablets. This paper presents a new spectrofluorimetric approach for detecting PZM in tablets and human blood plasma (spiked with PZM). The detection mechanism depends on the inhibition of the PZM molecule's photoinduced electron transfer (PET), resulting in a bright fluorescent intensity from PZM. Acetic acid (2.0 M) acidifies the reaction environment and causes PET inhibition. This approach detects PZM at concentrations ranging from 100 to 700 ng mL-1. Furthermore, the approach has outstanding detection and quantification limits of 30.95 and 93.78 ng mL-1, respectively. Also, the approach accurately measured PZM content homogeneity in each tablet and spiked human plasma samples without any interference. This new strategy represents a new and sensitive method for accurate PZM monitoring in different samples. Furthermore, the established fluorimetric method's greenness was evaluated.

Current advances in the management of cluster headaches

Introduction: Cluster headache (CH) is probably the most severe idiopathic pain condition, yet its current medical management remains poor.Areas covered: Only repurpose medicines are currently in use for the prevention of CH, partially because the pathophysiology of the condition is still elusive. In this article we performed a systematic review to evaluate the evidence for efficacy of the currently available or emerging treatments for CH.Expert opinion: We found several ongoing randomized clinical trials testing prophylactic treatments for CH and only few for the standard ones. Recent data from randomized trials with monoclonal antibodies targeting the calcitonin gene related peptide pathway (anti-CGRP mAbs) are controversial, although its role in the pathogenesis of the condition is well documented. This inconsistency may depict inadequacies in clinical trial designing. Anti-CGRP mAbs and antagonists of pituitary adenylate cyclase-activating polypeptide (PACAP) along with neuromodulation techniques, are curing the necessary valuable evidence that could illuminate the therapeutical future for cluster headache. Orexin pathway is another attractive target for CH treatment. To improve the evidence for efficacy, we further propose that the design of the clinical trials for CH needs to be radically reviewed to allow more patients to participate.

Pizotifen inhibits the proliferation and invasion of gastric cancer cells

Gastric cancer is the fifth most common malignancy and the third highest cause of cancer-associated mortality worldwide. Therefore, research on the pathogenesis of gastric cancer is of utmost importance. It has been reported that aberrant activation of the Wnt/β-catenin signaling pathway is involved in the occurrence and development of gastric cancer. In the present study, it was found that pizotifen could inhibit the viability of gastric cancer cell lines MNK45 and AGS cells in a dose-dependent manner. Pizotifen treatment suppressed cell migration and invasion in MNK45 and AGS cells, whilst also inducing apoptosis. Western blot analysis demonstrated that pizotifen blocked the expression of Wnt3a, β-catenin and N-cadherin, whilst increasing E-cadherin expression. In addition, BML-284, a pharmacological Wnt signaling activator, partially reversed the changes in the expression levels of β-catenin, N-cadherin and E-cadherin in MNK45 and AGS cells induced by pizotifen. Collectively, these findings suggested that pizotifen demonstrates potential as a novel anti-cancer drug for the treatment of gastric cancer by inhibiting the Wnt/β-catenin pathway.

Cluster headache: present and future therapy

Cluster headache is characterized by severe, unilateral headache attacks of orbital, supraorbital or temporal pain lasting 15-180 min accompanied by ipsilateral lacrimation, rhinorrhea and other cranial autonomic manifestations. Cluster headache attacks need fast-acting abortive agents because the pain peaks very quickly; sumatriptan injection is the gold standard acute treatment. First-line preventative drugs include verapamil and carbolithium. Other drugs demonstrated effective in open trials include topiramate, valproic acid, gabapentin and others. Steroids are very effective; local injection in the occipital area is also effective but its prolonged use needs caution. Monoclonal antibodies against calcitonin gene-related peptide are under investigation as prophylactic agents in both episodic and chronic cluster headache. A number of neurostimulation procedures including occipital nerve stimulation, vagus nerve stimulation, sphenopalatine ganglion stimulation and the more invasive hypothalamic stimulation are employed in chronic intractable cluster headache.

Putative role of 5-HT2B receptors in migraine pathophysiology

Objective

In this review we attempt to characterize the acute and chronic role of 5-HT2B receptors with regard to meningeal nociception in animal experiments and clinical data targeting migraine therapy.

Background

Migraine is a common disabling neurovascular primary headache disease, the pathomechanism of which is still unclear. Serotonin (5-HT) and its receptors might play an important role in some aspects of migraine pathogenesis. The ability of the unselective 5-HT2B receptor agonist m-chlorophenylpiperazine to induce migraine attacks in migraine sufferers, the high affinity of prophylactic antimigraine drugs to this receptor and its expression in migraine-relevant structures like the dura mater argue for a role of 5-HT2B receptors in the pathogenesis of migraine attacks.

Methods

For this review, the relevant databases such as PubMed, MEDLINE®, Cochrane Library and EMBASE, respectively, were searched to December 2015 using the keywords “migraine, 5-HT2, trigeminal, neurogenic inflammation, nitric oxide, nitroxyl, vasodilatation, plasma protein extravasation” and combinations thereof.

Conclusion

Our literature review suggests an important role of 5-HT2B receptor activation in meningeal nociception and the generation of migraine pain.

Evidence-based treatments for cluster headache

Cluster headache (CH), one of the most painful syndromes known to man, is managed with acute and preventive medications. The brief duration and severity of the attacks command the use of rapid-acting pain relievers. Inhalation of oxygen and subcutaneous sumatriptan are the two most effective acute therapeutic options for sufferers of CH. Several preventive medications are available, the most effective of which is verapamil. However, most of these agents are not backed by strong clinical evidence. In some patients, these options can be ineffective, especially in those who develop chronic CH. Surgical procedures for the chronic refractory form of the disorder should then be contemplated, the most promising of which is hypothalamic deep brain stimulation. We hereby review the pathogenesis of CH and the evidence behind the treatment options for this debilitating condition.

Cluster headache: focus on emerging therapies

Cluster headache is a strictly unilateral headache that occurs in association with cranial autonomic features. It is an excruciating syndrome and is probably one of the most painful conditions known to mankind with female patients describing each attack as being worse than childbirth. In most patients, it has a striking circannual and circadian periodicity. This disorder has a highly stereotyped clinical phenotype and responds to specific therapies, thereby underlying the importance of distinguishing it from other primary headache syndromes. In this review, the clinical manifestations, differential diagnosis, diagnostic workup and treatment options for this syndrome have been outlined.

Cluster headache: pharmacological treatment and neurostimulation

Cluster headache is a primary headache syndrome that is characterized by excruciatingly severe, strictly unilateral attacks of orbital, supraorbital or temporal pain, which last 15-180 min and are accompanied by ipsilateral autonomic manifestations (e.g. lacrimation and rhinorrhea). The attacks typically occur with circadian rhythmicity, being experienced at fixed hours of the day or night. In episodic cluster headache, attacks usually occur daily in 6-12-week bouts (cluster periods) followed by remission periods. In chronic cluster headache there is no notable remission. Cluster headache attacks reach full intensity very quickly and abortive agents need to be administered without delay. The pathophysiology of cluster headache is imperfectly understood and treatment has so far been mainly empirical. However, neuroimaging studies have prompted the successful use of hypothalamic stimulation to treat the condition. More recently, the less invasive technique of occipital nerve stimulation has shown promise in drug-refractory chronic cluster headache. This Review discusses both acute and preventive treatments for cluster headache and includes suggestions of how to use the available medications. The rationale, study results and selection criteria for neurostimulation procedures are also summarized, as are the disadvantages of these procedures.

Management of migraine in Australian general practice

OBJECTIVES

To determine the proportion of patients who have a diagnosis of migraine in a sample of Australian general practice patients, and to review the prophylactic and acute drug treatments used by these patients.

DESIGN, SETTING AND PARTICIPANTS

A cohort of general practitioners collected data from about 30 consecutive patients each as part of the BEACH (Bettering the Evaluation and Care of Health) program; this is a continuous national study of general practice activity in Australia. The migraine substudy was conducted in June-July 2005 and December 2005-January 2006.

MAIN OUTCOME MEASURES

Proportion of patients with a current diagnosis of migraine; frequency of migraine attacks; current and previous drug treatments; and appropriateness of treatment assessed using published guidelines.

RESULTS

191 GPs reported that 649 of 5663 patients (11.5%) had been diagnosed with migraine. Prevalence was 14.9% in females and 6.1% in males. Migraine frequency in these patients was one or fewer attacks per month in 77.1% (476/617), two per month in 10.5% (65/617), and three or more per month in 12.3% (76/617) (missing data excluded). Only 8.3% (54/648) of migraine patients were currently taking prophylactic medication. Patients reporting three or more migraines or two migraines per month were significantly more likely to be taking prophylactic medication (19.7% and 25.0%, respectively) than those with less frequent migraine attacks (3.8%) (P < 0.0001). Prophylactic medication had been used previously by 15.0% (96/640). The most common prophylactic agents used currently or previously were pizotifen and propranolol; other appropriate agents were rarely used, and inappropriate use of acute medications accounted for 9% of "prophylactic treatments". Four in five migraine patients were currently using acute medication as required for migraine, and 60.6% of these medications conformed with recommendations of the National Prescribing Service. However, non-recommended drugs were also used, including opioids (38% of acute medications).

CONCLUSIONS

Migraine is recognised frequently in Australian general practice. Use of acute medication often follows published guidelines. Prophylactic medication appears to be underutilised, especially in patients with frequent migraine. GPs appear to select from a limited range of therapeutic options for migraine prophylaxis, despite the availability of several other well documented efficacious agents, and some use inappropriate drugs for migraine prevention.

Trigeminal-autonomic headaches in daily clinical practice

Following the revised International Headache Society criteria, a group of short-lasting headaches associated with autonomic symptoms, the so called trigeminal autonomic cephalgias, were newly recognized. The trigeminal autonomic cephalgias include cluster headache, paroxysmal hemicranias and a syndrome involving short-lasting unilateral neuralform cephalgias with conjunctival injection and tearing (SUNCT) syndrome. In all of these syndromes, the half-sided head pain and cranial autonomic symptoms are prominent. All of the trigeminal autonomic cephalgias differ in duration, frequency and rhythmicity of the attacks, the intensity of pain and autonomic symptoms, as well as treatment options. This review gives a brief clinical description of the headache disorders and recent pathophysiological findings, as well as an overview of the treatment of cluster headache, paroxysmal hemicranias and SUNCT syndrome.

EFNS guidelines on the treatment of cluster headache and other trigeminal-autonomic cephalalgias

Cluster headache and the other trigeminal-autonomic cephalalgias [paroxysmal hemicrania, short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT) syndrome] are rare but very disabling conditions with a major impact on the patient's quality of life. The objective of this study was to give evidence-based recommendations for the treatment of these headache disorders based on a literature search and consensus amongst a panel of experts. All available medical reference systems were screened for any kind of studies on cluster headache, paroxysmal hemicrania and SUNCT syndrome. The findings in these studies were evaluated according to the recommendations of the European Federation of Neurological Societies resulting in level A, B or C recommendations and good practice points. For the acute treatment of cluster headache attacks, oxygen (100%) with a flow of at least 7 l/min over 15 min and 6 mg subcutaneous sumatriptan are drugs of first choice. Prophylaxis of cluster headache should be performed with verapamil at a daily dose of at least 240 mg (maximum dose depends on efficacy or tolerability). Although no class I or II trials are available, steroids are clearly effective in cluster headache. Therefore, the use of at least 100 mg methylprednisone (or equivalent corticosteroid) given orally or at up to 500 mg i.v. per day over 5 days (then tapering down) is recommended. Methysergide, lithium and topiramate are recommended as alternative treatments. Surgical procedures, although in part promising, require further scientific evaluation. For paroxysmal hemicranias, indomethacin at a daily dose of up to 225 mg is the drug of choice. For treatment of SUNCT syndrome, large series suggest that lamotrigine is the most effective preventive agent, with topiramate and gabapentin also being useful. Intravenous lidocaine may also be helpful as an acute therapy when patients are extremely distressed and disabled by frequent attacks.

Cluster headache: pathogenesis, diagnosis, and management

Cluster headache is a stereotyped primary pain syndrome characterised by strictly unilateral severe pain, localised in or around the eye and accompanied by ipsilateral autonomic features. The syndrome is characterised by the circadian rhythmicity of the short-lived attacks, and the regular recurrence of headache bouts, which are interspersed by periods of complete remission in most individuals. Headaches often start about 1-2 h after falling asleep or in the early morning, and show seasonal variation, suggesting that the hypothalamus has a role in the illness. Consequently, the vascular theory has been superseded by recognition that neurovascular factors are more important. The increased familial risk suggests that cluster headache has a genetic component in some families. Neuroimaging has broadened our pathophysiological view and has led to successful treatment by deep brain stimulation of the hypothalamus. Although most patients can be treated effectively, some do not respond to therapy. Fortunately, time to diagnosis of cluster headache has improved. This is probably the result of a better understanding of the pathophysiology in combination with efficient treatment strategies, leading to a broader acceptance of the syndrome by doctors.

Management of trigeminal autonomic cephalgias and hemicrania continua

The trigeminal autonomic cephalgias (TACs) are a group of primary headache disorders characterised by unilateral trigeminal distribution pain that occurs in association with ipsilateral cranial autonomic features. This group of headache disorders includes cluster headache, paroxysmal hemicrania and short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT syndrome). Although hemicrania continua has previously been classified amongst the TACs, its nosological status remains unclear. Despite their similarities, these disorders differ in their clinical manifestations and response to therapy, thus underpinning the importance of recognising them. We have outlined the clinical manifestations, differential diagnoses, diagnostic workup and the treatment options for each of these syndromes.

Cluster headache: aetiology, diagnosis and management

Cluster headache is characterised by repeated attacks of strictly unilateral pain in the orbital region associated with local autonomic symptoms or signs. The attacks are brief but of a very severe, almost excruciating intensity. For unknown reasons males are affected more often than females. Recent studies suggest that an autosomal dominant gene has a role in some families with cluster headache. Hormonal studies indicate a dysfunction in the central nervous system. Neuroimaging has revealed primary defects in the hypothalamic grey matter. Local homolateral dilatation in the intracranial segment of the internal carotid and ophthalmic arteries during attacks is the result of a generic neurovascular activation, probably mediated by trigeminal parasympathetic reflexes. Sumatriptan 6mg subcutaneously is the drug of choice in the treatment of acute attacks. Inhalation of 100% oxygen can also be recommended. In the prophylactic treatment, verapamil is the first option. Other drugs that can be considered are corticosteroids, which may induce a remission of frequent, severe attacks, and lithium. Oral ergotamine tartrate may be sufficient for patients with night attacks and/or short, rather mild to moderately severe cluster headache periods. Third line drugs are serotonin inhibitors (methysergide and pizotifen) and valproic acid. Patients should be encouraged to keep headache diaries and be carefully instructed about the nature and treatment of the headaches. Alcohol can bring on extra attacks and should not be consumed during active periods of cluster headache.

Migraine: helping clients choose treatment and identify triggers

Migraine is a common complaint causing untold difficulties or aggravation for the sufferer. Clients with migraine can have very real fears of possible pathologies and the nurse is in a strong position to dispel these fears with information and reassurance. This article discusses information and knowledge which nurses can use to enable clients to take control over their migraine: from the range of choices about treatment to the identification of triggers that precipitate migraine or identification of factors to inhibit attacks. Treatments may be broad ranging from non-pharmacological to pharmacological approaches, which may be either symptomatic or prophylactic. Pharmacological treatments are presented in detail indicating the range of types from analgesia to antidepressants.

A review of the treatment of primary headaches. Part I: Migraine

Finding the best treatment for a patient's migraine is often a problem in clinical practice since the condition is very common, often debilitating and may prove refractory to therapy. Over recent years, more effective migraine treatments have been found and validated, and the traditional remedies have undergone controlled testing. This article reviews the various therapies available for both the acute treatment and prevention of migraine. Treatments often effective against migraine attacks are: aspirin, analgesics, non steroid anti-inflammatory drugs (NSAIDs), ergot derivatives and sumatriptan. Five main classes of prophylactic drug are currently used: beta-blockers, calcium antagonists, serotonin modulators, NSAIDs and ergot compounds. Biofeedback, one of the most efficacious non-pharmacological preventive treatments of migraine, is also discussed. The variables influencing the choice of acute and preventive treatments, including contraindications and drug availability, are also described in order to provide a practical and up-to-date guide to migraine therapy.

The antiserotonin agent pizotifen does not increase endurance performance in humans

This study investigated the effect of the serotonin receptor antagonist pizotifen on endurance performance during treadmill exercise in humans. Eight healthy men exercised to exhaustion on a treadmill at an intensity corresponding to 70% of their maximal oxygen uptake (VO2max). Pizotifen was administered orally in a 1-mg dose 5 h before the start of exercise. The study was double blind, using a randomized, placebo-controlled crossover design. Oxygen uptake, heart rate, and ratings of perceived exertion were measured and blood samples taken for determination of concentrations of lactate, glucose, amino acids, ammonia, and haematocrit. Measurements were made at intervals of 30 min during the run and at exhaustion. There was no significant difference between the placebo and the pizotifen trials for any of the variables except for the plasma free-tryptophane: branched chain amino acid ratio which was somewhat lower after pizotifen at postexercise. Pizotifen did not increase exercise time to exhaustion, which was even shorter after pizotifen than after placebo in seven out of the eight subjects; the difference between pizotifen and placebo did not reach the level of statistical significance [109.4 (SD 6.7) min after pizotifen versus 119.8 (SD 12.5) min after placebo]. The results do not support the hypothesis that there is a central component to fatigue which is mediated by the serotoninergic neurones.

Is migraine related to the eating disorders?

Migraine and the eating disorders, particularly bulimia nervosa, share some common demographics, phenomenology, psychopathology, and treatments. Bulimics also appear to be more sensitive to the induction of severe migrainous headaches than controls following challenge with the 5-HT agonist, m-chlorophenylpiperazine (m-CPP), but not placebo or L-tryptophan. This supports a common pathophysiological relationship involving postsynaptic 5-HT dysfunction between these disorders. In order to further explore the possible relationship between eating disorders and migraine, we administered a modified version of the Diagnostic Survey of the Eating Disorders (DSED) and the Eating Disorders Inventory (EDI) to a group of female migraine patients attending the Medical University of South Carolina (MUSC) Neurology Clinic (n = 34). Of the 34 migraine patients surveyed, 88% reported dieting behavior, 59% reported binge eating, and 26% reported self-induced vomiting during their lifetimes. Compared to the responses of a group of normal female controls (n = 577), patients with migraine had elevated scores on four of the eight subscales of the EDI: Body Dissatisfaction (p < or = .02), Perfectionism (p < or = .01), Interpersonal Distrust (p < or = .02), and Ineffectiveness (p < or = .06). These findings support the hypothesis that common pathophysiological mechanisms, perhaps involving 5-HT dysregulation, may be involved in these two disorders.

Affinity profiles of pizotifen, ketotifen and other tricyclic antimuscarinics at muscarinic receptor subtypes M1, M2 and M3

The affinity of pizotifen, ketotifen and other tricyclic antimuscarinic drugs for different muscarinic receptor subtypes was investigated in vitro in functional experiments with field-stimulated vas deferens of the rabbit (M1 and M2 receptors) and with ileum and trachea of the guinea-pig (M3 receptors). All compounds were competitive antagonists in the three tissues. Like the close analogue cyproheptadine (pA2 = 7.99-8.08), pizotifen (pA2 = 7.23-7.81) and ketotifen (pA2 = 6.34-6.99) were devoid of selectivity for the receptor subtypes studied. Thiazinamium, although exhibiting high affinity for muscarinic receptors (pA2 = 7.83-8.51), was found to be non-selective. In contrast, the novel pirenzepine analogue nuvenzepine was selective for M1 receptors (pA2 = 6.63-7.74). The lack of selectivity of cyproheptadine, pizotifen and ketotifen is reflected in the chemical structures of these drugs. All three antagonists are composed of a very similar tricyclic ring system linked to a 1-methyl-4-piperidylene ring. The finding that thiazinamium, pizotifen and cyproheptadine were potent muscarinic antagonists and possessed non-selective affinity characteristics may have therapeutic implications.

Pharmacology of antimigraine drugs

The drugs used in migraine therapy can be divided into two groups: agents that abort an established migraine attack and agents used prophylactically to reduce the number of migraine attacks. Both groups have drugs that are specific for migrainous headaches and that are non-specific, and are used to treat the accompanying headache (analgesics), vomiting (anti-emetics), anxiety (sedatives and anxiolytics), or depression (antidepressants). The main drugs with specific action on migraine include ergot alkaloids (ergotamine, dihydroergotamine), agonists (sumatriptan) or partial agonists (methysergide) at a specific subtype of 5-HT1-like receptors, beta-adrenoceptor antagonists (propranolol, metoprolol), calcium antagonists (flunarizine) and anti-inflammatory agents (indomethacin). The pharmacological basis of therapeutic action of several of these drugs is not well understood. In the case of the ergot alkaloids and 5-HT1-like receptor agonists, however, it is likely that the antimigraine effect is related to the potent and rather selective constriction of the large arteries and arteriovenous anastomoses in the scalp and dural regions. In addition, these drugs inhibit plasma extravasation into the dura in response to trigeminal ganglion stimulation, but it is possible that this effect is related to the selective vasoconstriction in the extracerebral vascular bed. The selectivity of the pharmacological effects of these antimigraine drugs (constriction of the extracerebral arteries and arteriovenous anastomoses, poor penetration into the central nervous system and the absence of an antinociceptive effect even after intrathecal administration) strongly suggests that excessive dilatation in the extracerebral cranial vasculature, probably initiated by a neuronal event, is an integral part of the pathophysiology of migraine.

Behavioural changes on diet selection and serotonin (5-HT) turnover in rats under pizotifen treatment

The effects of pizotifen on protein and carbohydrate self-selection in rats over a seven-day period, and on 5-HT turnover was studied. Four groups of male Wistar rats were individually caged and ad lib fed with a standard (SD) and (50%) carbohydrate-enriched diet (CED), sweet (diet group I) or not (diet group II). Food intake was measured daily 4 hr after IP injection of pizotifen (2.5 mg/kg) or vehicle. 5-HT and 5-HIAA in the hypothalamus (Hy), striatum (St) and hippocampus (Hi) were assayed on the 8th day of the experiment. Pizotifen increased the consumption of SD. The absolute intake of CED remained totally and daily unchanged, while the percentage proportion was reduced. Total food intake was increased by the drug which seemed to affect the proportion rather than the absolute amounts of carbohydrate and protein consumed. This effect was independent of the carbohydrate taste. There was a decrease of 5-HT levels in the Hi, while 5-HIAA/5-HT ratio was increased in the Hy and in the Hi of animals that consumed sweet carbohydrate. The above data suggest a role of pizotifen on 5-HT central metabolism and diet selection and support the view that changes of 5-HT metabolism in the Hy and Hi are responsible for protein selection and the regulation of SD/CED ratio, but they cannot explain drug's effect on total food intake.

Failure of serotonin antagonist pizotifen to stimulate feeding or weight gain in free-feeding rats

The serotonin antagonist pizotifen (BC-105) is prescribed as an appetite and weight enhancer (Mosegor--Wander, also commercialized under brand names Sanmigran or Sandomigran--Sandoz, Switzerland) for anorectic and convalescent humans. There has been, however, difficulty in demonstrating any orexigenic effect of pizotifen in laboratory animals. In the present report, the influence of chronic administration of pizotifen (0.1-30.0 mg/kg b.wt. per day, SC) on food intake and body weight gains was studied in rats given a standard diet (SD-energy content 14.5 kJ/g, 9% fibre), and in rats either habituated to a low energy content, carbohydrate-free diet (DD-7.3 kJ/g, 45% fibre), or given the DD after habituation to the SD. Pizotifen failed to increase food intake or weight gain. Nor did it shorten a period of initial depression of intake of the unfamiliar DD. On the contrary, pizotifen seemed to diminish food intake and weight gain in rats fed the low energy content diet. Since it has been reported that other 5-HT antagonists, e.g., cyproheptadine, methysergide, and ritanserin can enhance feeding, it is of some interest that pizotifen failed to affect food intake or weight gain in rats. The results suggest that the effects of pizotifen (and, possibly, of serotonin) in rats may differ from those in man. The possibility that feeding in the rat is mediated by 5-HT1 rather than 5-HT2 receptors is discussed.

Reduction of negative alliesthesia for sweet gustatory stimuli by cyproheptadine, a serotonin antagonist

Cyproheptadine (CH) is a serotonin antagonist that increases food intake and body weight. In order to elucidate its mechanism of action on the control of food intake, hunger ratings, pleasure-displeasure to sweet gustatory stimuli and negative alliesthesia induced by a 50 g glucose load were compared in 14 healthy subjects after they had received a placebo or 16 mg of CH. Cyproheptadine did not affect the hunger rating, nor the affective rating in fasted subjects, but it reduced significantly the negative alimentary alliesthesia induced by the glucose load. It was concluded that CH increases food intake more by reducing satiation than by increasing hunger. This is in line with the anti-serotoninergic properties of CH, and the action of serotonin on the control of food intake.

Serotonergic modulation of ingestive behavior in pigeons

The effects of peripheral administration of the serotonin agonist zimeldine and the serotonin antagonist cyproheptadine on food and water consumption were evaluated in domestic pigeons. Injections of zimeldine reduced the amount of feeding and drinking dose-dependently in 24-hr fasted animals. Administration of cyproheptadine enhanced food and water consumption dose-dependently up to a dose of 160 micrograms per 100 g body weight in nondeprived pigeons. Higher doses reduced ingestion probably due to a general behavioral depression. The effect of zimeldine was antagonized by cyproheptadine. It is concluded that, as in mammals, serotonin participates as an inhibitor in the regulation of feeding in birds. Contrary to the situation in mammals it has no activating effect on drinking but leads to a reduction of water consumption in pigeons.

Inhibition of passive cutaneous anaphylaxis by several histamine (H1) and serotonin antagonists in the rat

Drugs of the pizotifen type (pizotifen, cyproheptadine), possessing high H1-antihistamine and high antiserotonin activities in animal experiments, exert potent inhibitory actions on the passive cutaneous anaphylaxis (PCA) reaction in the rat. The drug pipethiadene, a 4,9-dihydrothieno(2,3-c)-2-benzothiepin derivative also belongs to this group. Selective histamine H1-antagonists alone are unable to cause pronounced reduction of the intensity of the PCA reaction in the rat, but in local reactions induced in rats by compound 48/80, histamine H1-receptors seem to play major role.

Efficacy of nimodipine in comparison with pizotifen in the prophylaxis of migraine

The efficacy of nimodipine in comparison with that of pizotifen was assessed in the prophylaxis of migraine in a double-blind cross-over study, in which a double-dummy technique was also utilized. The study was carried out on 43 migraine patients, of whom 15 had classic and 28 had common migraine. A 4-week run-in placebo period preceded the drug treatments, the drug treatments lasted 12 weeks, and there was a washout placebo period of 4 weeks between nimodipine and pizotifen treatments. The dosages used were 40 mg three times daily for nimodipine and 0.5 mg three times daily for pizotifen. Both nimodipine and pizotifen proved to be better than placebo, the number of migraine attacks showing a significant reduction. There was no difference between nimodipine and pizotifen in antimigrainous efficacy, but there were fewer side effects during the nimodipine period. The results suggest that nimodipine is an effective drug for the prophylaxis of migraine, with few side effects and therapeutic efficacy equal to that of pizotifen.

Abdominal migraine: a childhood syndrome defined

It has long been recognized that some cases of recurrent abdominal pain in children are related to migraine, but the diagnostic criteria for abdominal migraine have not been defined. We have identified a group of children with recurrent abdominal pain who had a family history of migraine--in over half the cases in a first-degree relative--and who obtained marked relief from their symptoms from specific anti-migraine therapy. These children had a well-defined syndrome comprising episodes of midline abdominal pain of sufficient severity to interfere with normal activities and lasting for prolonged periods, frequently accompanied by pallor, headache, anorexia, nausea, and vomiting. It is proposed that these children have "abdominal migraine".

Further studies on the dose-dependent stimulus properties of 5-methoxy-N,N-dimethyltryptamine

Twenty-two rats were trained to discriminate either 1.5 mg/kg of 5-methoxy-N,N-dimethyltryptamine (5-OMe DMT) from saline in a standard two-lever operant procedure. Once responding was stable, various doses of several serotonin (5-HT) antagonists, i.e., cyproheptadine (CYP), methysergide (UML), cinanserin (CIN), and methergoline (MCE), were administered in combination with 5-OMe DMT, to assess the ability of each antagonist to attenuate each 5-OMe DMT-stimulus. The 5-OMe DMT-stimulus at 1.5 mg/kg was completely antagonized by CYP, and was partially attenuated by CIN and MCE. UML had negligible effects on 5-OMe DMT-appropriate responding. In the 3.0 mg/kg 5-OMe DMT-trained rats, UML and MCE partially blocked the 5-OMe DMT-stimulus; CYP and CIN had no significant effect on 5-OMe DMT-appropriate responding. The results suggest that until the in vivo effects and mechanism of action of 5-OMe DMT and certain 5-HT antagonists are better understood, caution is advised when conclusions are drawn from studies employing these agents.

Antagonism of a peripheral vascular but not an apparently central serotonergic response by xylamidine and BW 501C67

Xylamidine and BW501C67 (alpha-anilino-N-2-m-chlorophenoxypropylacetamidine), serotonin antagonists that have been reported not to cross the blood-brain barrier, were compared to other serotonin antagonists: mianserin, ketanserin, metergoline and LY 53857. All six compounds were potent inhibitors of the binding of tritiated spiperone to 5HT2 receptors in rat frontal cortex membranes in vitro and were less potent inhibitors of the binding of tritiated serotonin to 5HT1 receptors in rat brain membranes. All were potent antagonists of the 5HT2 receptor-mediated contractile response to serotonin in the rat jugular vein in vitro. At doses of 0.1 and 0.3 mg/kg i.p., xylamidine and BW501C67 antagonized the pressor response to intravenously injected serotonin in pithed rats. In contrast, neither xylamidine nor BW501C67 at doses of 1 or 3 mg/kg i.p. antagonized the elevation of serum corticosterone concentration by quipazine in rats, although the other compounds antagonized this effect with ED50 values between 0.03 and 0.9 mg/kg. These data corroborate the previously reported antiserotonin activity of xylamidine and BW501C67. Since xylamidine and BW501C67 were potent antagonists of a peripheral serotonergic response in vivo, their inability to antagonize the elevation of serum corticosterone concentration by quipazine suggests that this effect results from activation of central serotonin receptors.

Pizotifen (BC-105) attenuates orienting and Pavlovian heart rate conditioning in rabbits

The cardiac component of the orienting reflex (OR) was elicited in rabbits by 75 dB, 4-sec duration tones of either 304 or 1216 Hz. The conditioned cardiac response was also studied using the same tones and paraorbital electric shock as conditioned and unconditioned stimuli, respectively, using a differential Pavlovian conditioning paradigm. Subcutaneous injections of the central 5-HT antagonist pizotifen (BC-105), the peripheral 5-HT antagonist xylamidine, the central 5-HT agonist d-lysergic acid diethylamide (LSD), and LSD in conjunction with BC-105 were administered 15 min prior to behavioral assessment. Both the heart rate (HR) conditioned response (CR) and the OR consisted of bradycardia. BC-105 attenuated, but xylamidine had no effect on, OR habituation. LSD reduced the magnitude of the OR, an effect which was blocked by BC-105. BC-105 also produced a dose-related attenuation of the bradycardiac HR CR; however, xylamidine had no effect on HR conditioning, suggesting that the attenuation of the HR CR by BC-105 was central rather than peripheral in origin. LSD potentiated the bradycardiac HR CR, but BC-105 in conjunction with LSD attenuated this response. These results suggest that central 5-HT neurons may modulate the magnitude of bradycardiac responses during orienting and aversive Pavlovian conditioning.

The pharmacotherapy of migraine

The relative importance of neural and humoral components in the pathogenesis of migraine has yet to be determined, but there is circumstantial evidence that implicates noradrenaline and serotonin as neural or humoral mediators in the recurrent headache, neurological and gastrointestinal symptoms that comprise the migraine syndrome. The treatment of migraine includes the avoidance of precipitating factors when possible, psychological counselling and relaxation training. Pharmacotherapy can be considered rationally in terms of agents acting on receptors that may possibly play a part in the mechanism of migraine.

Neurochemical mechanism of action of drugs which modify feeding via the serotoninergic system

The neurochemical mechanisms by which drugs acting on central serotoninergic system modify feeding were reviewed. Fenfluramine, a clinically effective appetite suppressant, releases serotonin from nerve terminals and inhibits its reuptake, and considerable evidence suggests that these effects mediate its anorectic activity. The D isomer of fenfluramine is particularly specific in affecting serotonin mechanisms and causing anorexia. Transmitters other than serotonin such as acetylcholine, catecholamines and GABA are also affected by systemic administration of fenfluramine, but some of these effects are secondary to fenfluramine's action on serotoninergic mechanisms. Moreover, there is no evidence that these brain substances are involved in fenfluramine's ability to cause anorexia. Several studies with drugs affecting different serotonin mechanisms such as release and uptake or mimicking the action of serotonin at post-synaptic receptors suggest that increase serotonin release and direct stimulation of postsynaptic receptors are the most effective mechanisms for causing depression of food intake, although inhibition of serotonin uptake may also contribute in appropriate conditions. Development of serotonin receptor hyposensitivity and, in some instances, decreased serotonin levels may lead to tolerance to the anorectic activity of drugs enhancing serotonin transmission, the degree of this depending critically on the type of effect on serotonin mechanisms and intensity and duration of serotonin receptor activation. Recent evidence suggests that a decrease in serotonin function causes stimulation of feeding. This may lead to development of new strategies for the treatment of clinical anorexias.

Mechanisms involved in the vasodilator action of 5-hydroxytryptamine in the dog femoral arterial circulation in vivo

The possibility that the vasodilator effect of 5-hydroxytryptamine (5-HT) in vivo involves a presynaptic inhibitory effect on sympathetic nerve activity was investigated in the femoral arterial circulation of pentobarbitone-anaesthetized dogs. The vasodilator effect of intraarterial (i.a.) 5-HT was abolished following ganglion blockade with mecamylamine, and remained inhibited after restoration of femoral vascular tone with i.a. ornipressin. These procedures had no effect on the vasodilator response to i.a. acetylcholine. The vasoconstrictor response to i.a. noradrenaline was not inhibited by mecamylamine. These findings suggest that a presynaptic inhibition of sympathetic neurotransmission is responsible for 5-HT-induced vasodilatation in vivo. Pizotifen (0.1-0.4 mg/kg i.v.) inhibited the 5-HT dilator response, but the doses required were too high to be commensurate with an action at 'D' type 5-HT receptors. Ketanserin (0.1-0.4 mg/kg i.v.) specifically inhibited the dilator response to 5-HT; higher doses (1-4 mg/kg i.v.) also inhibited noradrenaline-induced vasoconstriction. Ketanserin, at all doses used, reduced systemic blood pressure and femoral vascular resistance. The effects of the lower doses of ketanserin (0.1-0.4 mg/kg) cannot be due to peripheral alpha-adrenoceptor antagonism; blockade of the dilator effect of 5-HT may simply be due to inhibition of sympathetic nerve activity by ketanserin itself.

Calcium channel antagonism by pizotifen

Pizotifen is a clinically effective anti-migraine agent with potent anti-serotonin and anti-histamine properties. Pizotifen is equipotent in blocking contractions of the canine basilar artery induced by serotonin, norepinephrine or calcium chloride. As a result, the primary action of pizotifen in the canine basilar artery system appears to be calcium channel blockade and not selective antagonism of serotonin or norepinephrine. Calcium channel blocking ability may be related to the clinical efficacy of pizotifen in the treatment of migraine.

Metoprolol and pizotifen in the prophylactic treatment of classical and common migraine. A double-blind investigation

The prophylactic anti-migraine effect of the serotonin antagonist pizotifen and the beta 1-selective beta-adrenoceptor antagonist metoprolol was compared in a double-blind cross-over study. The dosage of pizotifen was 0.5 mg t.i.d. and that of metoprolol 50 mg b.i.d. Thirty-five patients with classical or common migraine were included in the investigation. Five patients withdrew during the course of the study; four because of side effects (three on pizotifen, one on metoprolol) and one because of unassociated illness. The results show that there was no statistically significant difference in efficacy between metoprolol and pizotifen. The tolerance, especially regarding weight gain, was the major drawback with pizotifen, while metoprolol was generally well tolerated.

Redistribution of carotid artery blood flow by 5-HT: effects of the 5-HT2 receptor antagonists ketanserin and Wal 1307

The study concerned effects of ketanserin and a new 5-HT2 receptor antagonist, Wal 1307, on the responses to 5-hydroxytryptamine (5-HT) in the porcine common carotid vascular bed. More than 80% of the total carotid blood flow (208 +/- 18 ml; n = 12) bypassed the tissues via arteriovenous anastomoses. Intracarotid infusions of 5-HT (2 micrograms X kg-1 X min-1) reduced the total carotid blood flow by about 50% and arteriovenous anastomotic flow by 85% but extracerebral tissue (nutrient) blood flow more than tripled. The cerebral component did not change. Thus, 5-HT appears to constrict large conducting arteries and arteriovenous anastomoses but dilates arterioles. Ketanserin and Wal 1307 did not affect carotid blood flow distribution but completely blocked the amine-induced reduction of total carotid blood flow. The constriction of arteriovenous anastomoses was only slightly reduced but the 5-HT-induced arteriolar, vasodilation was enhanced. We conclude that vasoconstriction in the main trunk of the carotid artery and, to a smaller degree, in the arteriovenous anastomoses and arterioles, is mediated by mediated by 5-HT2 receptors. The major part of the constriction of arteriovenous anastomoses and arteriolar dilation elicited by 5-HT is, however, not mediated by 5-HT2 receptors. It is argued that these 'atypical' 5-HT receptors may be related to 5-HT1 binding sites.

Serotonin antagonists

The realisation that serotonin plays a role not only in the carcinoid syndrome but also in migraine, nociception, dumping syndrome, vascular disease and hypertension, has led to an enormous amount of activity in search of serotonin antagonists. Numerous such pharmacological agents have been identified but only few have found their way into clinical use. All of them are competitive serotonin inhibitors, in that they vie for the same receptor as the amine itself and are thus able to block its action as well as imitate its effects. By far the widest use of such inhibitors is in the prevention of migraine, where they have effectively eliminated the dread of an attack from the life of the majority of patients. Whilst useful in the control of diarrhea in patients with carcinoid and dumping syndromes, their role in these diseases is limited. However, the possible role of serotonin in hypertension and nociception opens new avenues in the use of existing serotonin antagonists and calls for the discovery of a new generation of such pharmacological agents for the control of these conditions.

Discriminative stimulus properties of pizotifen maleate (BC105): a putative serotonin antagonist

Rats were trained to discriminate the putative serotonin (5-HT) antagonist, pizotifen maleate (BC105), from saline using a two-lever drug discrimination paradigm. Pizotifen maleate (6 mg/kg, 14.6 mumol/kg, IP) or saline was administered 55 min prior to the operant training session. The pizotifen discriminative stimulus (DS) had a rapid onset (less than 7 min) and was of long duration. The pizotifen DS was dose dependent. The pizotifen DS did not generalize to the putative 5-HT antagonists, methiothepin, xylamidine, and cinanserin. Partial generalization was observed to methysergide and metergoline, and complete generalization to cyrproheptadine and the phenothiazine antihistamine, promethazine. The pizotifen DS failed to generalize to the antipsychotic chlorpromazine, the ethanolamine antihistamine diphenhydramine, the CNS stimulant, d-amphetamine, and the putative 5-HT agonists, LSD and quipazine. LSD and quipazine failed to antagonize the pizotifen DS. The results of this study suggest that different DS properties are associated with the different putative 5-HT antagonists and that pizotifen and cyproheptadine, in addition to their reported 5-HT antagonist properties, share a common property that is also associated with promethazine, probably involving antihistaminergic activity.