Dopamine D2 receptor blockade and antimigraine action of flunarizine

Imaging the brain and vascular reactions to headache treatments: a systematic review

BACKGROUND

Neuroimaging studies have made an important contribution to our understanding of headache pathophysiology. This systematic review aims to provide a comprehensive overview and critical appraisal of mechanisms of actions of headache treatments and potential biomarkers of treatment response disclosed by imaging studies.

MAIN BODY

We performed a systematic literature search on PubMed and Embase databases for imaging studies investigating central and vascular effects of pharmacological and non-pharmacological treatments used to abort and prevent headache attacks. Sixty-three studies were included in the final qualitative analysis. Of these, 54 investigated migraine patients, 4 cluster headache patients and 5 patients with medication overuse headache. Most studies used functional magnetic resonance imaging (MRI) (n = 33) or molecular imaging (n = 14). Eleven studies employed structural MRI and a few used arterial spin labeling (n = 3), magnetic resonance spectroscopy (n = 3) or magnetic resonance angiography (n = 2). Different imaging modalities were combined in eight studies. Despite of the variety of imaging approaches and results, some findings were consistent. This systematic review suggests that triptans may cross the blood-brain barrier to some extent, though perhaps not sufficiently to alter the intracranial cerebral blood flow. Acupuncture in migraine, neuromodulation in migraine and cluster headache patients, and medication withdrawal in patients with medication overuse headache could promote headache improvement by reverting headache-affected pain processing brain areas. Yet, there is currently no clear evidence for where each treatment acts, and no firm imaging predictors of efficacy. This is mainly due to a scarcity of studies and heterogeneous treatment schemes, study designs, subjects, and imaging techniques. In addition, most studies used small sample sizes and inadequate statistical approaches, which precludes generalizable conclusions.

CONCLUSION

Several aspects of headache treatments remain to be elucidated using imaging approaches, such as how pharmacological preventive therapies work, whether treatment-related brain changes may influence therapy effectiveness, and imaging biomarkers of clinical response. In the future, well-designed studies with homogeneous study populations, adequate sample sizes and statistical approaches are needed.

Emerging drugs for the preventive treatment of migraine: a review of CGRP monoclonal antibodies and gepants trials

INTRODUCTION

Migraine is a leading cause of years lived with disability and preventive strategies represent a mainstay to reduce health-related disability and improve quality of life of migraine patients. Until a few years ago, migraine prevention was based on drugs developed for other clinical indications and relocated in the migraine therapeutic armamentarium, characterized by unfavourable tolerability profiles. The advent of monoclonal antibodies against Calcitonin Gene-Related Peptide (CGRP) and gepants, CGRP receptor antagonists, has been a turning point in migraine prevention owing to advantageous efficacy, safety and tolerability profiles.Nevertheless, while in an ideal scenario a drug characterized by significant greater efficacy and tolerability compared to existing therapeutic strategies should be adopted as a first-line treatment, cost-effectiveness analyses available for monoclonal antibodies against CGRP pathway tend to limit their administration to more severe migraine phenotypes.

AREAS COVERED

The present narrative review aim to provide a critical appraisal of phase II and III CGRP-mAbs and gepants trials to analyse their use in clinical practice.

EXPERT OPINION

Despite monoclonal antibodies against CGRP pathway and gepants can be undoubtedly considered top-of-the-range treatments, there are still issues deserving to be addressed in the coming years as the risk of off-target effects as well as their economic sustainability based on the considerable migraine burden.

Refractory migraine profile in CGRP-monoclonal antibodies scenario

Objective

Refractory migraine (Ref‐M) represents a conundrum that headache experts have to face with. We aim to investigate whether a peculiar profile may characterize patients with Ref‐M according to 2020 European Headache Federation criteria. Furthermore, to substantiate a dysfunctional dopaminergic pathway involvement in these patients, we explored the effectiveness of olanzapine.

Materials & Methods

Eighty‐four patients (fitting previous Ref‐M criteria of the 2014) were treated with erenumab for six months. Differences between clinical and demographic features of responder (Ref‐M according to 2014 criteria) and not‐responder (Ref‐M according to 2020 criteria) patients to CGRP‐mAbs were investigated and their predictive values assessed. In fifteen patients with Ref‐M not responders to CGRP‐mAbs, olanzapine was administered (5 mg/die) for 3 months and frequency and pain intensity of migraine attacks were estimated.

Results

Patients with Ref‐M not responsive to CGRP‐mAbs (29/84) when compared with Ref‐M responsive to CGRP‐mAbs showed higher baseline frequency of migraine attacks, medication overuse and pain catastrophizing scale (PCS) scores. Logistic regression analyses showed that frequency of attacks, medication overuse and PCS score represent independent negative predictors of CGRP‐mAbs response. A ≥50% reduction of headache days/month was observed after olanzapine treatment in 67% of patients with Ref‐M not responsive to CGRP‐mAbs.

Conclusions

We outline that higher frequency of migraine attacks, medication overuse and pain catastrophizing characterize patients with Ref‐M not responsive to CGRP‐mAbs. In this frame, olanzapine effectiveness on frequency and pain intensity of migraine attacks supports the hypothesis that migraine refractoriness may be subtended by a prominent involvement of the dopaminergic pathway.

In Silico Repositioning of Dopamine Modulators with Possible Application to Schizophrenia: Pharmacophore Mapping, Molecular Docking and Molecular Dynamics Analysis

We have performed theoretical calculations with 70 drugs that have been considered in 231 clinical trials as possible candidates to repurpose drugs for schizophrenia based on their interactions with the dopaminergic system. A hypothesis of shared pharmacophore features was formulated to support our calculations. To do so, we have used the crystal structure of the D2-like dopamine receptor in complex with risperidone, eticlopride, and nemonapride. Linagliptin, citalopram, flunarizine, sildenafil, minocycline, and duloxetine were the drugs that best fit with our model. Molecular docking calculations, molecular dynamics outcomes, blood-brain barrier penetration, and human intestinal absorption were studied and compared with the results. From the six drugs selected in the shared pharmacophore features input, flunarizine showed the best docking score with D2, D3, and D4 dopamine receptors and had high stability during molecular dynamics simulations. Flunarizine is a frequently used medication to treat migraines and vertigo. However, its antipsychotic properties have been previously hypothesized, particularly because of its possible ability to block the D2 dopamine receptors.

Medication overuse and drug addiction: a narrative review from addiction perspective

Chronic headache is particularly prevalent in migraineurs and it can progress to a condition known as medication overuse headache (MOH). MOH is a secondary headache caused by overuse of analgesics or other medications such as triptans to abort acute migraine attacks. The worsening of headache symptoms associated with medication overuse (MO) generally ameliorates following interruption of regular medication use, although the primary headache symptoms remain unaffected. MO patients may also develop certain behaviors such as ritualized drug administration, psychological drug attachment, and withdrawal symptoms that have been suggested to correlate with drug addiction. Although several reviews have been performed on this topic, to the authors best knowledge none of them have examined this topic from the addiction point of view. Therefore, we aimed to identify features in MO and drug addiction that may correlate. We initiate the review by introducing the classes of analgesics and medications that can cause MOH and those with high risk to produce MO. We further compare differences between sensitization resulting from MO and from drug addiction, the neuronal pathways that may be involved, and the genetic susceptibility that may overlap between the two conditions. Finally, ICHD recommendations to treat MOH will be provided herein.

Other Preventive Anti-Migraine Treatments: ACE Inhibitors, ARBs, Calcium Channel Blockers, Serotonin Antagonists, and NMDA Receptor Antagonists

PURPOSE OF REVIEW

Migraine causes more years of life lived with disability than almost any other condition in the world and can significantly impact the lives of individuals with migraine, their families, and society. The use of medication for the prevention of migraine is an integral component to reducing disability caused by migraine. There are many different drug classes that have been investigated and shown efficacy in migraine prophylaxis. This article examines several of the classes of medications that are used for migraine preventive treatment, specifically, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, calcium channel blockers, serotonin antagonists, alpha-adrenergic agonists, and N-methyl-D-aspartic acid receptor antagonists.

RECENT FINDINGS

There have been randomized control trials investigating medications in these drug classes since the most recent guidelines for migraine prevention in adults were published by the American Academy of Neurology, American Headache Society, and the Canadian Headache Society. In these investigations, enalapril, candesartan, and memantine all demonstrated efficacy for migraine prevention. The evidence for these and the aforementioned drug classes are reviewed. When oral medications are being selected for migraine prevention, comorbid and coexistent medical conditions, concomitant medications, patient preference, and pregnancy and breast-feeding plans should be considered. Within the drug classes discussed, memantine and candesartan have a moderate level of evidence for efficacy.

Flunarizine versus topiramate for chronic migraine prophylaxis: a randomized trial

OBJECTIVES

Chronic migraine (CM) is a prevalent and devastating disorder with limited therapeutic options. This study explored the efficacy of 10 mg/d flunarizine for CM prophylaxis as compared with 50 mg/d topiramate.

METHODS

We conducted a prospective, randomized, open-label, blinded-endpoint trial. Patients with CM were randomized to flunarizine and topiramate treatment. The primary outcomes assessed were the reductions in the total numbers of headache days and migraine days after 8 weeks of treatment. Secondary outcomes were reductions in the numbers of days of acute abortive medication intake and acute abortive medication tablets taken, and the 50% responder rate.

RESULTS

Sixty-two subjects were randomized (n=31/group). Patients treated with flunarizine showed significant reductions in the numbers of total headache days (-4.9 vs -2.3, P=.012) and migraine days (-4.3 vs -1.4, P=.001) compared with those treated with topiramate. Patients treated with flunarizine also showed significant reductions in the numbers of days of acute abortive medication intake (-2.3 vs -0.2, P=.005) and acute abortive medication tablets taken (-4.6 vs -0.5, P=.005) and had a higher 50% responder rate in terms of total headache days (58.6% vs 25.9%, P=.013) and migraine days (75.9% vs 29.6%, P=.001), compared with topiramate-treated patients. Flunarizine was generally well tolerated and had a safety profile comparable to that of topiramate.

CONCLUSIONS

Our results suggest that, in an 8-week study, 10 mg/d flunarizine is more effective than 50 mg/d topiramate for CM prophylaxis.

Dopamine and Migraine: Biology and Clinical Implications

In the last 30 years dopamine has been considered as playing a role in the pathogenesis of migraine. The literature indicates that migraineurs are hypersensitive to dopamine agonists with respect to some of the premonitory symptoms of migraine such as nausea and yawning. There are various nonspecific dopamine D2 receptor antagonists that show good clinical efficacy in migraine, and also a number of polymorphisms of dopaminergic genes related to migraine. Animal studies have also shown that dopamine receptors are present in the trigeminovascular system, the area believed to be involved in headache pain, and neuronal firing here is reduced by dopamine agonists. There appears to be little effect of dopamine on peripheral trigeminal afferents. We assess some of the limitations of the clinical studies with regard to the therapeutics, and those found in the studies that discovered differences in genetic polymorphisms in migraine, and consider the implications of this on a dopaminergic hypothesis of migraine.

Acquired equivalence and related memory processes in migraine without aura

Introduction

Interictal deficits of elementary visuo-cognitive functions are well documented in patients with migraine and are mostly explained in terms of neocortical hyperexcitability. It has been suggested that the basal ganglia and the hippocampi might also be affected in migraine. If so, a deterioration of learning and memory processes related to these structures is expected.

Methods

A visual learning paradigm thought to be capable of dissociating learning/memory processes mediated by the basal ganglia from processes mediated by the hippocampus (the Rutgers Acquired Equivalence Test) was applied to a group of patients with migraine without aura and to age- and sex-matched controls.

Results

Patients with migraine showed a significantly poorer performance in both main phases of the test and the deficit in the phase considered to be dependent on the hippocampi was especially marked.

Conclusions

These results can be interpreted as behavioural support for findings that have suggested the involvement of the basal ganglia and the hippocampi in migraine, but further research is needed to clarify these findings.

Dopaminergic symptoms in migraine

Migraine pain is often preceded, accompanied and followed by dopaminergic symptoms (premonitory yawning and somnolence, accompanying nausea and vomiting, postdromal somnolence, euphoria and polyuria). After reviewing evidence from pharmacological, biochemical, genetic and animal experimental studies on the relationship between dopamine and migraine, and matching these data with patients' clinical features, we postulate that migraine attacks could be characterized by an ictal dopamine release in a subject with dopamine receptor hypersensitivity due to a chronic dopaminergic deficit synergistic to serotoninergic impairment. Our review suggests that when the attack begins, a low dopamine plasma concentration stimulates hypersensitive central presynaptic dopamine receptors thus causing prodromal symptoms such as yawning and somnolence. Increasing dopamine levels, though still insufficient to stop trigeminovascular activation, stimulate postsynaptic dopamine receptors thus inducing nausea, vomiting and hypotension. Finally, dopamine levels slowly return to baseline, giving rise to somnolence and fatigue, but, in some cases, continue to rise triggering postdromal symptoms such as euphoria and polyuria.

Overview of diagnosis and management of paediatric headache. Part II: therapeutic management

A thorough evaluation of headache in children and adolescents is necessary to make the correct diagnosis and initiate treatment. In part 1 of this article (Özge et al. in J Headache Pain, 2010), we reviewed the diagnosis of headache in children and adolescents. In the present part, we will discuss therapeutic management of primary headaches. An appropriate management requires an individually tailored strategy giving due consideration to both non-pharmacological and pharmacological measures. Non-pharmacological treatments include relaxation training, biofeedback training, cognitive-behavioural therapy, different psychotherapeutic approaches or combinations of these treatments. The data supporting the effectiveness of these therapies are less clear-cut in children than in adults, but that is also true for the data supporting medical treatment. Management of migraine and TTH should include strategies relating to daily living activities, family relationships, school, friends and leisure time activities. In the pharmacological treatment age and gender of children, headache diagnosis, comorbidities and side effects of medication must be considered. The goal of symptomatic treatment should be a quick response with return to normal activity and without relapse. The drug should be taken as early as possible and in the appropriate dosage. Supplementary measures such as rest in a quiet, darkened room is recommended. Pharmaco-prophylaxis is only indicated if lifestyle modification and non-pharmacological prophylaxis alone are not effective. Although many prophylactic medications have been tried in paediatric migraine, there are only a few medications that have been studied in controlled trials. Multidisciplinary treatment is an effective strategy for children and adolescents with improvement of multiple outcome variants including frequency and severity of headache and school days missed because of headache. As a growing problem both children and families should be informed about medication overuse and the children's drug-taking should be checked.

Does the antimigraine action of flunarizine involve the dopaminergic system? A clinical-neuroendocrinological study

We have investigated the prolactin response to bromocriptine (BRC), a D2 dopamine receptor agonist in migrainous women before and after treatment with flunarizine. We evaluated whether this test was predictive of therapeutic efficacy of flunarizine treatment and whether the therapeutic response to flunarizine treatment was related to its effect on dopaminergic system at tuberoinfundibular level. Ten migrainous women underwent a BRC test in the late follicular phase before and after 1 and 3 months of treatment with flunarizine 10 mg at bedtime. Blood samples of prolactin (PRL), growth hormone, follicle-stimulating hormone, luteinizing hormone, estradiol and progesterone were taken at basal condition. PRL was also evaluated 1 and 2 h after BRC (2.5 mg) administration. Each patient kept a daily headache diary for 1 month prior to the test and throughout the study. The level of PRL inhibition after BRC administration, observed before flunarizine treatment, was not predictive of the therapeutic response observed after 1 and 3 months of treatment. The effect of flunarizine on PRL level was not related to the therapeutic efficacy of the drug. These data suggest that flunarizine does not attenuate the activity of dopaminergic neurons in migrainous patients, and that the antimigraine effect of flunarizine does not seem related to its action on dopaminergic system at least at tuberoinfundibular level.

Dopamine and migraine: a review of pharmacological, biochemical, neurophysiological, and therapeutic data

The dopamine theory of migraine pathogenesis, first proposed by F. Sicuteri in 1977, has attracted renewed interest after an increased frequency of the dopamine D2 receptor (DRD2) gene allele NcoI C was found in patients with migraine with aura. Therefore we reviewed the relevant literature. The most compelling argument favoring an interictal hypersensitivity of dopamine receptors in migraineurs stems from pharmacologic studies of the gastric and autonomic effects of dopaminergic agents such as apomorphine, but none of these studies was blinded and placebo-controlled. Various DRD2 antagonists abort migraine attacks after parenteral administration, while there is circumstantial evidence that dopamine agonists may be useful for prophylaxis. Most drugs used in these trials, however, lack selectivity for dopamine receptors. Both in pharmacological and therapeutic studies most patients had migraine without aura. We conclude that data suggesting a primary role for the dopaminergic system in migraine pathogenesis are unconvincing. Based on well established interactions between central amines, a reduced release of serotonin between attacks could lower dopamine release which would lead to receptor hypersensitivity.

Long-term follow-up after flunarizine or nimodipine discontinuation in migraine patients

Various open and controlled studies have confirmed the antimigraine action of flunarizine, while the antimigraine properties of nimodipine are still open to controversy. Moreover, only a few studies include an additional follow-up after discontinuation of migraine prophylaxis with either drug. We carried out a single blind evaluation of the efficacy and tolerance of flunarizine (25 patients) in comparison with nimodipine (25 patients) and the long-term effect after discontinuation of a 6-month treatment. Both medications significantly reduced migraine frequently and severity. Flunarizine was more efficacious than nimodipine in reducing migraine frequency (p < 0.001), pain severity (p < 0.05), migraine index (p < 0.05) and corrected migraine index (p < 0.05). The positive effect lasted 8.4 +/- 4.0 months after discontinuation of flunarizine and 4.9 +/- 3.5 months after nimodipine (p < 0.05). Our results suggest that flunarizine is more effective than nimodipine in the prophylactic treatment of migraine. The positive effect after drug discontinuation lasts longer with flunarizine, compared to nimodipine.

Increased density of dopamine D5 receptor in peripheral blood lymphocytes of migraineurs: a marker for migraine?

The expression of dopamine D5 receptor was investigated in peripheral blood lymphocytes of 11 migraine patients and of ten healthy control subjects using a radioligand binding technique with [3H]SCH 23390 as a ligand. [3H]SCH 23390 is a benzazepine derivative with potent antagonist properties at the dopamine D1-like receptors. [3H]SCH 23390 was specifically bound to peripheral blood lymphocytes of migraineurs and control subjects in a manner consistent with the labelling of a dopamine D5 receptor. In migraineurs a statistically significant higher density of lymphocyte dopamine D5 receptor compared with controls was noticeable, whereas the affinity of the radioligand was unchanged. The increased density of dopamine D5 receptor in peripheral blood lymphocytes may reflect the dopaminergic hypersensitivity displayed by migraineurs and may represent a relatively simple and reliable peripheral marker of altered dopaminergic function.