The Discovery and Development of the Triptans, a Major Therapeutic Breakthrough

Triptans in the Acute Migraine Management of Children and Adolescents: An Update

PURPOSE OF REVIEW

To summarize recent findings regarding triptan use in the acute treatment of pediatric migraine.

RECENT FINDINGS

Prevalence of pediatric migraine is rising. The American Headache Society and American Academy of Neurology updated guidelines to provide evidence-based recommendations for the treatment of acute migraine in youth. In the setting of a dearth of new randomized controlled trials (RCTs), we review current guidelines, triptan use in the emergency department, and an era of secondary analyses. Measuring the efficacy of triptans in pediatric migraine has been challenged by high placebo response rates. Secondary analyses, combining data from multiple RCTs, support that triptans are safe and effective in the treatment of migraine. Triptans are a vital tool and the only FDA-approved migraine-specific treatment available in pediatrics. There is a need for further studies and funding support in pediatric headache medicine.

Serotonin syndrome in the acute treatment landscape of migraine: the lasmiditan experience

Background

Serotonin syndrome (SS) symptoms overlap with adverse events associated with lasmiditan, a 5-HT (serotonin)1F receptor agonist for acute treatment of migraine. Because SS symptoms are heterogeneous, diagnosis can be challenging, and potential cases observed with lasmiditan treatment led to questions about SS pathophysiology. Here, we provide an overview of the potential risk of SS based on experience with lasmiditan.

Methods

Results of eight phase 2 and phase 3 lasmiditan trials (n = 5,916) and a controlled intravenous trial of lasmiditan (n = 88) were analyzed for symptomatology consistent with SS. Post-marketing surveillance data from lasmiditan's US launch date (January 2020) until data cut-off (April 2021) were also examined. Established Sternbach and Hunter diagnostic criteria were used for formal determination of SS.

Results

Of 6,004 lasmiditan-treated clinical trial patients, 15 reported ≥1 treatment-emergent adverse event consistent with signs and symptom(s) of SS. After review, one case met Sternbach and Hunter criteria, two cases potentially met Sternbach criteria, and three cases reported as SS had limited/no information to determine if either criterion was met. During post-marketing surveillance (approximately 13,400 lasmiditan prescriptions), 17 cases with symptom complexes consistent with SS were reported; 3/17 cases had adequate case descriptions to apply predefined criteria. Of these, two met Sternbach and Hunter criteria, and one met Sternbach criteria.

Conclusion

Awareness of clinical symptomatology and diagnostic criteria of SS can help clinicians with recognition of rare instances of SS that may occur with lasmiditan.

Clinical trial registration

NCT03670810, NCT00384774, NCT00883051, NCT02565186.

The vascular role of CGRP: a systematic review of human studies

Intravenous infusion of human alpha calcitonin gene-related peptide (h-α-CGRP) has been applied to explore migraine pathogenesis and cerebral hemodynamics during the past three decades. Cumulative data implicate h-α-CGRP in regulating the vascular tone. In this systematic review, we searched PubMed and EMBASE for clinical studies investigating the vascular changes upon intravenous infusion of h-α-CGRP in humans. A total of 386 studies were screened by title and abstract. Of these, 11 studies with 61 healthy participants and 177 participants diagnosed with migraine were included. Several studies reported hemodynamic effects including flushing, palpitation, warm sensation, heart rate (HR), mean arterial blood pressure (MABP), mean blood flow velocity of middle cerebral artery (mean V_MCA), and diameter of superficial temporal artery (STA). Upon the start of h-α-CGRP infusion, 163 of 165 (99%) participants had flushing, 98 of 155 (63%) participants reported palpitation, and 160 of 165 (97%) participants reported warm sensation. HR increased with 14%-58% and MABP decreased with 7%-12%. The mean V_MCA was decreased with 9.5%-21%, and the diameter of the STA was dilated with 41%-43%. The vascular changes lasted from 20 to >120 min. Intravenous infusion of h-α-CGRP caused a universal vasodilation without any serious adverse events. The involvement of CGRP in the systemic hemodynamic raises concerns regarding long-term blockade of CGRP in migraine patients with and without cardiovascular complications.

The association between migraine and dementia - a national register-based matched cohort study

OBJECTIVES

Migraine and dementia, two major public health challenges, are associated, but more knowledge is needed to understand their relationship. Objectives of this study were to investigate 1) the association between non-self-reported measures of migraine and dementia, and whether dementia was associated with 2) migraine without aura (MO) and with aura (MA) in combination with migraine medication use, and 3) migraine severity operationalized as the number of migraine prescriptions.

STUDY DESIGN

Matched cohort study.

METHODS

National register data were obtained from individuals born between 1934 and 1958. Migraine cases (aged 25-58 years) were identified by migraine diagnoses and redeemed migraine medication. Migraine cases were matched with non-cases (N = 340,850) and date of diagnosis or medication redemption was defined as index year. Dementia was identified by dementia diagnoses and redeemed dementia medication.

RESULTS

We observed a 1.46 (95% CI: 1.26-1.69) times higher dementia rate in individuals with a migraine diagnosis and a 0.86 (95% CI: 0.76-0.97) times lower rate when using migraine medication. We found the highest dementia rate among individuals with MA, who also used migraine medication (HR = 2.23; 95% CI: 1.19-4.17), and the lowest rate among individuals with MO, who also used medication (HR = 1.25; 95% CI: 0.75-2.10). The number of migraine medication prescriptions was not associated with dementia.

CONCLUSIONS

Being registered with a migraine diagnosis was associated with a higher dementia rate, while use of prescribed migraine medication was not. The differences in the dementia rate among migraine cases identified via diagnoses versus medications warrants further investigation.

Effectiveness of Calcitonin Gene-Related Peptide Receptor Antagonists for Migraine Treatment: A Meta-Analysis

INTRODUCTION

The pathophysiology of migraine has been researched incessantly, and it has been suggested that calcitonin gene-related peptide (CGRP) is associated with migraine attacks. CGRP receptor blockers are attracting attention as potential agents for migraine prevention and treatment of acute episodes. This meta-analysis aimed to assess the effects of available CGRP receptor antagonists, focusing on their therapeutic doses for acute migraine treatment.

METHODS

We systematically searched MEDLINE and Embase from inception to March 27, 2021, for English-language publications using the keywords "migraine" and "calcitonin gene-related peptide"; the searches were limited to human studies.

RESULTS

Five studies that focused on examining the effects of CGRP receptor antagonists on acute migraine treatment met the eligibility criteria for this meta-analysis. A pooled analysis demonstrated that CGRP receptor antagonists significantly increased freedom from pain (odds ratio [OR] = 2.066, 95% confidence interval [CI] 1.766-2.418, I2 = 0%) and from bothersome symptoms in general (OR = 1.606, 95% CI = 1.408-1.830, I2 = 0%); reduced the intensity of pain (OR = 1.791, 95% CI = 1.598-2.008, I2 = 0%); and increased freedom from nausea (OR = 1.361, 95% CI = 1.196-1.548, I2 = 0%) compared to a placebo.

CONCLUSIONS

CGRP receptor antagonists are effective for acute migraine treatment and are expected to be used clinically as emerging therapeutic agents.

Epidemiology, Demographics, Triptan Contraindications, and Prescription Patterns of Patients with Migraine: A German Claims Database Study

Introduction

Migraine is a neurological disease with a considerable economic and societal burden that negatively impacts quality of life and productivity. Triptans are potent serotonin receptor agonists widely used to treat migraine attacks. Little is known about German patients with migraine diagnosed with triptan contraindications or those who discontinue triptans.

Methods

This retrospective observational study identifies adults with migraine from a German sickness fund database (2010–2018). Migraine prevalence was calculated for the database population and extrapolated to the German Statutory Health Insurance (SHI) population. Medication use, proportion and demographics of patients with triptan contraindications, prevalence of triptan discontinuation and use of triptans by patients with contraindications were analysed.

Results

In total 120,170 patients with migraine were identified in the database population, of whom 77.7% were female; migraine prevalence was 2.0% (male) and 7.3% (female), leading to an extrapolated 2,923,979 patients with migraine in the entire German SHI population (2019); of these, 14.5% had ≥ 1 triptan contraindication. The most frequent contraindication was a history of stroke/transient ischaemic attack. However, an extrapolated 25.9% of patients who had a triptan contraindication received a triptan prescription following diagnosis. We calculated that 975,698 patients in the entire German SHI population had ever received a triptan, of whom 596,364 did not receive a triptan prescription in the follow-up year. Of these 596,364 individuals, 96.6% continued to receive a migraine diagnosis after their last triptan prescription. These ‘triptan discontinuers’ were predominantly female (82.6%). Most patients utilized only one specific triptan, with a large majority of ongoing triptan users who had used this specific triptan receiving > 4 prescriptions.

Conclusion

We confirm the existence of German patients with migraine and unmet therapeutic needs. These are patients diagnosed with triptan contraindications or patients who have discontinued triptan use despite continued migraine attacks. More research is needed to ascertain reasons for triptan discontinuation and the risk of triptan use by patients with contraindications.

Acute Care and Treatment of Migraine

OBJECTIVE

Migraine is a chronic neurological disease involving the brain and its vasculature, typically characterized by recurrent attacks of moderate or severe throbbing headache, accompanied by sensitivity to light and sound, and associated with nausea, vomiting, and inability to move due to worsening of pain. About 30% of migraineurs have some type of aura, most often visual. Migraine attacks, if untreated or suboptimally treated, usually result in significant disability, requiring bed rest and resulting in poor quality of life. Increased frequency of attacks and overuse of acute care medication are significant risks for chronification, resulting in the transformation of episodic migraine into chronic migraine. We aim to review most acute care treatments for migraine.

METHODS

Current treatment options for migraine attacks were reviewed from the selected literature and combined with our clinical experience.

RESULTS

Current acute treatment options for migraine attacks include over-the-counter analgesics, at times combined with caffeine, nonsteroidal anti-inflammatory medications, opioids, and migraine-specific medications such as triptans and ergots. In the near future, we will probably have 3 gepants (small-molecule calcitonin gene-related peptide [CGRP] receptor antagonists). The first one was just approved in the United States. A ditan acting as a stimulator of 5-HT1F receptors, was also just approved by the FDA. Stimulation of the trigeminal, vagal, occipital, and even upper arm peripheral nerves through electrical nerve stimulation devices and magnetic stimulation devices are available as alternative, nondrug treatment options. Several devices have already been FDA-allowed for treatment in the United States and/or approved elsewhere, and others will follow soon. Behavioral medicine techniques such as biofeedback training and mindfulness have been available for some time and are often helpful.

CONCLUSION

A wide variety of acute care options to treat migraine are available, and others will soon be and will herein be described in further detail. Some medications have been approved by regulatory authorities in countries other than the United States, and some devices have been given a CE Mark in Europe.

International Union of Basic and Clinical Pharmacology. CX. Classification of Receptors for 5-hydroxytryptamine; Pharmacology and Function

5-HT receptors expressed throughout the human body are targets for established therapeutics and various drugs in development. Their diversity of structure and function reflects the important role 5-HT receptors play in physiologic and pathophysiological processes. The present review offers a framework for the official receptor nomenclature and a detailed understanding of each of the 14 5-HT receptor subtypes, their roles in the systems of the body, and, where appropriate, the (potential) utility of therapeutics targeting these receptors. SIGNIFICANCE STATEMENT: This review provides a comprehensive account of the classification and function of 5-hydroxytryptamine receptors, including how they are targeted for therapeutic benefit.

Targeting the 5-HT system: Potential side effects

Targeting the serotonin (5-HT) system is no simple task: there are at least 15 5-HT receptors, in addition to a number of transporters and metabolizing enzymes. Multiple 5-HT receptor variants exist due to genetic variations and/or post translational modifications, splice variants or editing variants. Some receptors may form homo and heteromers. The 5-HT system is targeted by multiple drugs to treat a variety of diseases. Given the homology amongst the 5-HT and neighbouring receptor classes, only few drugs are actually selective for a single target. In fact, many 5-HT drugs act on a combination of targets, i.e. several receptors and/or transporters or enzymes. For instance, a number of antidepressants or antipsychotics act on 5-HT and other transmitter systems. Recently developed drugs may show target selectivity by design, based on the current state of knowledge, whereas many older compounds hit multiple targets since they were developed using phenotypic screens, as was done well into the 1980's. Ergot analogues, antipsychotics or antidepressants, fall into this category. As our knowledge developed over the last 25-30 years, some targets have very well-defined liabilities: for instance, 5HT_2B or 5-HT_2A receptor agonists, will produce valvulopathies or hallucinations, respectively, whereas 5-HT₃ receptor antagonists, may lead to constipation. This short review will be limited in scope as there are multiple targets and even more compounds to discuss. This article is part of the special issue entitled 'Serotonin Research: Crossing Scales and Boundaries'.

Children with allergic diseases have an increased subsequent risk of migraine upon reaching school age

The association between migraine and allergy has remained a subject of debate for more than a century. To systemically investigate the interaction between children with antecedent allergic diseases and their future risks of migraine on reaching school age, we recruited 16,130 children aged 7-18 with migraine diagnosed between 2000 and 2008, and 64,520 matched controls without a history of migraine. The ORs of migraine were calculated for the association with allergic diseases diagnosed before migraine diagnosis. The allergic diseases included atopic dermatitis, allergic conjunctivitis, allergic rhinitis (AR), and asthma. Children with preceding allergic diseases had a greater subsequent risk of migraine than the controls. Among the four evaluated diseases, AR had the highest adjusted OR (aOR) of 2.17 (95% CI 2.09 to 2.26). Children with all four allergic diseases had the highest aOR of 3.59 (95% CI 2.91 to 4.44). Further, an increasing trend of aORs was observed with more allergic disease-associated medical consulting. Our study indicates that children with allergic diseases are at increased subsequent risk of migraine when they reach school age, and the risk shows a cumulative effect of more allergic diseases and more allergy-related healthcare.

Triptans and CGRP blockade - impact on the cranial vasculature

The trigeminovascular system plays a key role in the pathophysiology of migraine. The activation of the trigeminovascular system causes release of various neurotransmitters and neuropeptides, including serotonin and calcitonin gene-related peptide (CGRP), which modulate pain transmission and vascular tone. Thirty years after discovery of agonists for serotonin 5-HT1B and 5-HT1D receptors (triptans) and less than fifteen after the proof of concept of the gepant class of CGRP receptor antagonists, we are still a long way from understanding their precise site and mode of action in migraine. The effect on cranial vasculature is relevant, because all specific anti-migraine drugs and migraine pharmacological triggers may act in perivascular space. This review reports the effects of triptans and CGRP blocking molecules on cranial vasculature in humans, focusing on their specific relevance to migraine treatment.

5-HT Receptor Nomenclature: Naming Names, Does It Matter? A Tribute to Maurice Rapport

The naming of 5-HT receptors has been challenging, especially in the early days when the concept of multiple receptors for a single neurotransmitter was considered to be unrealistic at best. Yet pharmacological (rank orders of potency in functional or biochemical settings) and transductional evidence (second messengers, electrophysiology) clearly indicated the existence of receptor families and subfamilies. The genetic revolution, with the cloning and study of recombinantly expressed receptors, and eventually the cloning of the human and other genomes have made such reservations obsolete. Further, the advances in structural biology, with the possibility to study ligand receptor complexes as crystals and/or using solution NMR have largely confirmed the complexity of the 5-HT receptor system: species differences, existence of multiple receptor active and inactive states, splice variants, editing variants, complexes with multiple interacting proteins and transduction bias. This is a short personal history on how advances in biochemistry, molecular biology, biophysics, imaging and medicinal chemistry, some lateral thinking, and a decent amount of collaborative spirit within the 5-HT receptor nomenclature committee and the 5-HT community at large have helped to better define the pharmacology of the 5-HT receptor family.

Characterization of a mouse model of headache

Migraine and other primary headache disorders affect a large population and cause debilitating pain. Establishing animal models that display behavioral correlates of long-lasting and ongoing headache, the most common and disabling symptom of migraine, is vital for the elucidation of disease mechanisms and identification of drug targets. We have developed a mouse model of headache, using dural application of capsaicin along with a mixture of inflammatory mediators (IScap) to simulate the induction of a headache episode. This elicited intermittent head-directed wiping and scratching as well as the phosphorylation of c-Jun N-terminal kinase in trigeminal ganglion neurons. Interestingly, dural application of IScap preferentially induced FOS protein expression in the excitatory but not inhibitory cervical/medullary dorsal horn neurons. The duration of IScap-induced behavior and the number of FOS-positive neurons correlated positively in individual mice; both were reduced to the control level by the pretreatment of antimigraine drug sumatriptan. Dural application of CGRP(8-37), the calcitonin gene-related peptide (CGRP) receptor antagonist, also effectively blocked IScap-induced behavior, which suggests that the release of endogenous CGRP in the dura is necessary for IScap-induced nociception. These data suggest that dural IScap-induced nocifensive behavior in mice may be mechanistically related to the ongoing headache in humans. In addition, dural application of IScap increased resting time in female mice. Taken together, we present the first detailed study using dural application of IScap in mice. This headache model can be applied to genetically modified mice to facilitate research on the mechanisms and therapeutic targets for migraine headache.

Insights Into the Molecular Mechanism of Triptan Transport by P-glycoprotein

The P-glycoprotein (Pgp) transporter reduces the penetration of a chemically diverse range of neurotherapeutics at the blood-brain barrier, but the molecular features of drugs and drug-Pgp interactions that drive transport remain to be clarified. In particular, the triptan neurotherapeutics, eletriptan (ETT) and sumatriptan (STT), were identified to have a >10-fold difference in transport rates despite being from the same drug class. Consistent with these transport differences, ETT activated Pgp-mediated ATP hydrolysis ∼2-fold, whereas STT slightly inhibited Pgp-mediated ATP hydrolysis by ∼10%. The interactions between them were also noncompetitive, suggesting that they occupy different binding sites on the transporter. Despite these differences, protein fluorescence spectroscopy revealed that the drugs have similar affinity to the transporter. NMR with Pgp and the drugs showed that they have distinct interactions with the transporter. Tertiary conformational changes probed by acrylamide quenching of Pgp tryptophan fluorescence with the drugs and a nonhydrolyzable ATP analog implied that the STT-bound Pgp must undergo larger conformational changes to hydrolyze ATP than ETT-bound Pgp. These results and previous transport studies were used to build a conformationally driven model for triptan transport with Pgp where STT presents a higher conformational barrier for ATP hydrolysis and transport than ETT.

Growth of Headache Research: A 1983-2014 bibliometric study

Aim This study charts the growth of the scientific journal literature on headache for 30+ years (1983-2014). Methods Using the Web of Science, articles published in four two-year periods (1983-1984, 1993-1994, 2003-2004, 2013-2014) from journals indexed in the Science Citation Index Expanded database were retrieved and analyzed. Results From 1983-1984 to 2013-2014, the scientific literature on headache increased nearly fourfold (3.8) from 468 to 1776 articles; the number of participating countries more than doubled (26 to 67); and the two most prolific countries in each period were the USA and Italy. While several European countries (Italy, Germany, UK and Denmark) were among the top 10 in each period, the notable appearance of Turkey, China and Brazil among the top 10 in 2013-2014 indicates the growing geographic spread of publications on headache research. Meanwhile, the comet-like distribution of journals has not changed: two journals, Headache and Cephalalgia, persist throughout as the nucleus, with the tail increasing more than threefold from 141 journals in 1983-1984 to 462 in 2013-2014. Conclusion Our study follows the recent growth and spread of the scientific literature on headache research and should stimulate further bibliometric investigation in this field.

Lost but making progress--Where will new analgesic drugs come from?

There is a critical need for effective new pharmacotherapies for pain. The paucity of new drugs successfully reaching the clinic calls for a reassessment of current analgesic drug discovery approaches. Many points early in the discovery process present significant hurdles, making it critical to exploit advances in pain neurobiology to increase the probability of success. In this review, we highlight approaches that are being pursued vigorously by the pain community for drug discovery, including innovative preclinical pain models, insights from genetics, mechanistic phenotyping of pain patients, development of biomarkers, and emerging insights into chronic pain as a disorder of both the periphery and the brain. Collaborative efforts between pharmaceutical, academic, and public entities to advance research in these areas promise to de-risk potential targets, stimulate investment, and speed evaluation and development of better pain therapies.

Structure and function of serotonin G protein-coupled receptors

Serotonin receptors are prevalent throughout the nervous system and the periphery, and remain one of the most lucrative and promising drug discovery targets for disorders ranging from migraine headaches to neuropsychiatric disorders such as schizophrenia and depression. There are 14 distinct serotonin receptors, of which 13 are G protein-coupled receptors (GPCRs), which are targets for approximately 40% of the approved medicines. Recent crystallographic and biochemical evidence has provided a converging understanding of the basic structure and functional mechanics of GPCR activation. Currently, two GPCR crystal structures exist for the serotonin family, the 5-HT1B and 5-HT2B receptor, with the antimigraine and valvulopathic drug ergotamine bound. The first serotonin crystal structures not only provide the first evidence of serotonin receptor topography but also provide mechanistic explanations into functional selectivity or biased agonism. This review will detail the findings of these crystal structures from a molecular and mutagenesis perspective for driving rational drug design for novel therapeutics incorporating biased signaling.

Cranioselectivity of sumatriptan revisited: pronounced contractions to sumatriptan in small human isolated coronary artery

BACKGROUND

Initial concerns about the coronary side-effect potential of the anti-migraine drug sumatriptan and second-generation triptans initiated cranioselectivity studies using proximal human coronary arteries. However, myocardial ischaemia may originate from both large and small human coronary arteries.

METHODS

We investigated the contractions to sumatriptan in proximal (internal diameter 2-3 mm), distal (internal diameter 1,000-1,500 μm) and small (internal diameter 500-1,000 μm) human epicardial coronary arteries and compared these with contractions in the human middle meningeal artery. Concentration response curves to sumatriptan in human coronary arteries were constructed in the absence or presence of the 5-hydroxytryptamine1B (5-HT1B) receptor antagonist SB224289 and the 5-HT1D receptor antagonist BRL15572. The effect of sumatriptan on increased cyclic adenosine monophosphate (cAMP) levels induced by forskolin in proximal and distal coronary artery segments was investigated using a biochemical assay. Western blotting was used to analyse the 5-HT1B receptor density in the human arteries.

RESULTS

Contractions in the proximal human coronary artery were significantly smaller than those in the human meningeal artery, as we showed previously. In contrast, contractions to sumatriptan in distal and small human coronary arteries were not different from those in the human meningeal artery. The 5-HT1B receptor antagonist SB224289, but not the 5-HT1D receptor antagonist BRL15572, inhibited the contraction induced by sumatriptan in the coronary arteries. Moreover, in distal, but not in proximal, coronary arteries, sumatriptan inhibited the increase in cAMP levels induced by forskolin. Contrary to our expectations, the 5-HT1B receptor expression was more pronounced in the proximal human coronary artery than in the distal and small human coronary artery.

CONCLUSIONS

Based on functional experiments in distal and small human coronary arteries, contractions to sumatriptan are not as cranioselective as previously assumed. However, the vast clinical experience with sumatriptan and other triptans has proven that these drugs are cardiovascularly safe when contraindications are taken into account.

Understanding the pharmacology of headache

Migraine continues to be the most common of the debilitating headaches. Existing acute headache treatments are not always satisfactory, and current research is focussed on targeting neuroinflammatory pathways with drugs that are devoid of vascular action. Current prophylactic drugs are largely centred around antihypertensive, anticonvulsant and antidepressant drugs, although not all drugs of all sub-classes in these categories are effective. Selective agents which target the neuroinflammatory process including targets such as calcitonin gene related peptide, and PANNEXIN 1 may have clinical utility.

Pediatric migraine: abortive management in the emergency department

Studies suggest that headache accounts for approximately 1% of pediatric emergency department (ED) visits. ED physicians must distinguish between primary headaches, such as a tension or migraine, and secondary headaches caused by systemic disease including neoplasm, infection, or intracranial hemorrhage. A recent study found that 40% of children presenting to the ED with headache were diagnosed with a primary headache, and 75% of these were migraine. Once the diagnosis of migraine has been made, the ED physician is faced with the challenge of determining appropriate abortive treatment. This review summarizes the most recent literature on pediatric migraine with an emphasis on diagnosis and abortive treatment in the ED.

Studies on the pathophysiology and genetic basis of migraine

Migraine is a neurological disorder that affects the central nervous system causing painful attacks of headache. A genetic vulnerability and exposure to environmental triggers can influence the migraine phenotype. Migraine interferes in many facets of people's daily life including employment commitments and their ability to look after their families resulting in a reduced quality of life. Identification of the biological processes that underlie this relatively common affliction has been difficult because migraine does not have any clearly identifiable pathology or structural lesion detectable by current medical technology. Theories to explain the symptoms of migraine have focused on the physiological mechanisms involved in the various phases of headache and include the vascular and neurogenic theories. In relation to migraine pathophysiology the trigeminovascular system and cortical spreading depression have also been implicated with supporting evidence from imaging studies and animal models. The objective of current research is to better understand the pathways and mechanisms involved in causing pain and headache to be able to target interventions. The genetic component of migraine has been teased apart using linkage studies and both candidate gene and genome-wide association studies, in family and case-control cohorts. Genomic regions that increase individual risk to migraine have been identified in neurological, vascular and hormonal pathways. This review discusses knowledge of the pathophysiology and genetic basis of migraine with the latest scientific evidence from genetic studies.

Activation of 5-hydroxytryptamine1B/1D/1F receptors as a mechanism of action of antimigraine drugs

INTRODUCTION

The introduction of the triptans (5-hydroxytryptamine (5-HT)1B/1D receptor agonists) was a great improvement in the acute treatment of migraine. However, shortcomings of the triptans have prompted research on novel serotonergic targets for the treatment of migraine.

AREAS COVERED

In this review the different types of antimigraine drugs acting at 5-HT receptors, their discovery and development are discussed. The first specific antimigraine drugs were the ergot alkaloids, consisting of ergotamine, dihydroergotamine and methysergide, which are agonists at 5-HT receptors, but can also bind α-adrenoceptors and dopamine receptors. In the 1990s, the triptans became available on the market. They are 5-HT1B/1D receptor agonists, showing fewer side effects due to their receptor specificity. In the last years, compounds that bind specifically to 5-HT1D, 5-HT1F and 5-HT7 receptors have been explored for their antimigraine potential. Furthermore, the serotonergic system seems to act in tight connection with the glutamatergic as well as the CGRP-ergic systems, which may open novel therapeutic avenues.

EXPERT OPINION

Although the triptans are very effective in treating migraine attacks, their shortcomings have stimulated the search for novel drugs. Currently, the focus is on 5-HT1F receptor agonists, which seem devoid of vascular side effects. Moreover, novel compounds that affect multiple transmitter and/or neuropeptide systems that are involved in migraine could be of therapeutic relevance.

Sumatriptan: a review of its pharmacokinetics, pharmacodynamics and efficacy in the acute treatment of migraine

INTRODUCTION

Sumatriptan was developed more than 20 years ago as a 5-HT1B/1D receptor agonist, the first drug in a new class of specific anti-migraine drugs, the triptans. A large amount of information and experience has been gained from the clinical trials undertaken as well the various formulations of sumatriptan used over this period of time.

AREAS COVERED

This evaluation specifically reviews the pharmacokinetics, pharmacodynamics, clinical efficacy, and safety of different formulations and dosages of sumatriptan used for the acute treatment of migraines. Special clinical trials of the timing of dosage and sumatriptan in combination with other triptans as well as non-triptan drugs are also included.

EXPERT OPINION

Oral sumatriptan is effective, but not in a convincing majority (60%) of patients in clinical trials. Sumatriptan has failed to show superiority over more standard and cheaper treatment such as aspirin or aspirin plus metoclopramide. In addition, migraine patients want to quickly become pain free, and to remain pain free, but oral sumatriptan at 100 mg managed to keep patients pain free for 24 h is only 20% of cases. Even though sumatriptan has been a major step forward in providing a new specific therapy for the treatment of migraines, there are still are limitations in its use. There is still an unmet need to develop new non-triptan, anti-migraine drugs which act as effective treatment for those who suffer with migraines.

Drug interactions with triptans : which are clinically significant?

The triptans are a group of compounds with high efficacy for the acute treatment of migraine and cluster headache. They have a relatively wide therapeutic index, and although a number of minor pharmacokinetic interactions have been observed, few are likely to be clinically significant. Given the differences in principal elimination pathways, potentially interacting drugs on a pharmacokinetic basis are not common across all compounds. Of more concern than pharmacokinetic interactions are pharmacodynamic interactions. Of most concern, additive vasoconstrictor effects are likely to occur with other vasoconstrictors, especially the ergots used for migraine. Serotonin syndrome has been observed due to coadministration of triptans with selective serotonin reuptake inhibitors (SSRIs), but the absolute rate of such a clinical response to coadministration is probably low. Most patients can take triptans with other medications without dose alteration, although vigilance is required for pharmacodynamic interactions.

One hundred years of migraine research: major clinical and scientific observations from 1910 to 2010

Pain research, and headache research in particular, during the 20th century, has generated an enormous volume of literature promulgating theories, questions, and temporary answers. This narrative review describes the most important events in the history of migraine research between 1910 and 2010. Based on the standard textbooks of headache: Wolff's Headache (1948 and 1963) and The Headaches (1993, 2000, and 2006) topics were selected for a historical review. Most notably these included: isolation and clinical introduction of ergotamine (1918); further establishment of vasodilation in migraine and the constrictive action of ergotamine (1938); identification of pain-sensitive structures in the head (1941); Lashley's description of spreading scotoma (1941); cortical spreading depression (CSD) of Leão (1944); serotonin and the introduction of methysergide (1959); spreading oligemia in migraine with aura (1981); oligemia in the wake of CSD in rats (1982); neurogenic inflammation theory of migraine (1987); a new headache classification (1988); the discovery of sumatriptan (1988); migraine and calcitonin gene-related peptide (1990); the brainstem "migraine generator" and PET studies (1995); migraine as a channelopathy, including research from the genetic perspective (1996); and finally, meningeal sensitization, central sensitization, and allodynia (1996). Pathophysiological ideas have evolved within a limited number of paradigms, notably the vascular, neurogenic, neurotransmitter, and genetic/molecular biological paradigm. The application of various new technologies played an important role within these paradigms, in particular neurosurgical techniques, EEG, methods to measure cerebral blood flow, PET imaging, clinical epidemiological, genetic, and molecular biological methods, the latter putting migraine (at least hemiplegic migraine) within a completely new classification of diseases.

Paradoxical pharmacology: turning our pharmacological models upside down

Paradoxical pharmacology is a term first suggested by Richard Bond to refer to intriguing observations that chronic use of some drug types can have the opposite biological effect(s) to those seen following acute administration of the same drug. A good example of 'paradoxical pharmacology' is the research Richard has pioneered showing that whereas acute administration of β-blockers is contraindicated in the treatment of asthma, chronic use of certain β-blockers can have therapeutic benefit. It would appear that those β-blockers that can act as inverse agonists at the β2 receptor particularly show this paradoxical effect and the findings of Richard's research not only challenge the dogma of the treatment of asthma but also challenge many of the pharmacological principles of ligand/receptor interactions established by Sir James Black and others. In this paper, I discuss Richard's efforts to evaluate the chronic effects of β-blockers in the airways and how this research caught the imagination of Sir James Black.

Capillary endothelial Na(+), K(+), ATPase transporter homeostasis and a new theory for migraine pathophysiology

BACKGROUND

Cerebrospinal fluid sodium concentration ([Na(+)](csf)) increases during migraine, but the cause of the increase is not known.

OBJECTIVE

Analyze biochemical pathways that influence [Na(+)](csf) to identify mechanisms that are consistent with migraine.

METHOD

We reviewed sodium physiology and biochemistry publications for links to migraine and pain.

RESULTS

Increased capillary endothelial cell (CEC) Na(+), K(+), -ATPase transporter (NKAT) activity is probably the primary cause of increased [Na(+)](csf). Physiological fluctuations of all NKAT regulators in blood, many known to be involved in migraine, are monitored by receptors on the luminal wall of brain CECs; signals are then transduced to their abluminal NKATs that alter brain extracellular sodium ([Na(+)](e)) and potassium ([K(+)](e)).

CONCLUSIONS

We propose a theoretical mechanism for aura and migraine when NKAT activity shifts outside normal limits: (1) CEC NKAT activity below a lower limit increases [K(+)](e), facilitates cortical spreading depression, and causes aura; (2) CEC NKAT activity above an upper limit elevates [Na(+)](e), increases neuronal excitability, and causes migraine; (3) migraine-without-aura may arise from CEC NKAT over-activity without requiring a prior decrease in activity and its consequent spreading depression; (4) migraine triggers disturb, and treatments improve, CEC NKAT homeostasis; (5) CEC NKAT-induced regulation of neural and vasomotor excitability coordinates vascular and neuronal activities, and includes occasional pathology from CEC NKAT-induced apoptosis or cerebral infarction.

Migraine pain: reflections against vasodilatation

The original Wolff’s vascular theory of migraine was supported by the discovery of a class of drugs, the triptans, developed as a selective cephalic vasoconstrictor agents. Even in the neurovascular hypothesis of Moskowitz, that is the neurogenic inflammation of meningeal vessels provoked by peptides released from trigeminal sensory neurons, the vasodilatation provoked by calcitonin gene-related peptide (CGRP) is considered today much more important than oedema. The role of cephalic vasodilatation as a cause of migraine pain was recently sustained by studies showing the therapeutic effect of CGRP receptor antagonists. We discuss the evidence against vasodilatation as migraine pain generator and some findings which we suggest in support of a central (brain) origin of pain.