The clinical pharmacology, pharmacokinetics and metabolism of sumatriptan

Intranasal creatine administration increases brain creatine level and improves Barnes maze performance in rats

While skeletal muscle creatine levels can be enhanced by exogenous creatine supplementation, the elevation of brain creatine levels with oral creatine administration remains a challenge due to a lack of effective transportation of creatine through the blood-brain barrier. Intranasal administration can bypass the blood-brain barrier and deliver drugs directly to the brain. The purpose of this study was to assess the effect of intranasal administration of creatine on brain creatine level and cognitive performance. Rats were randomly assigned into three groups intranasal administration group, oral administration group, and control group. The intranasal group exhibited fewer errors and shorter primary latency compared to the control and oral groups, respectively, during the acquisition phase of the Barnes maze. The intranasal group spent a higher percentage of time in the target quadrant during the probe trial compared to the control group. Biochemical measurements showed that the concentration of creatine in the olfactory bulbs, medial prefrontal cortex, and hippocampus of the rats in the intranasal group was higher than in the oral, and control groups. These results indicate that intranasal administration of creatine hydrochloride increases the creatine level in the rat's brain's and improves their performance in the Barnes maze.

Neuroimaging in the pre-ictal or premonitory phase of migraine: a narrative review

BACKGROUND

The premonitory phase, or prodrome, of migraine, provides valuable opportunities to study attack initiation and for treating the attack before headache starts. Much that has been learned about this phase in recent times has come from the outcomes of functional imaging studies. This review will summarise these studies to date and use their results to provide some feasible insights into migraine neurobiology.

MAIN BODY

The ability to scan repeatedly a patient without radiation and with non-invasive imaging modalities, as well as the recognition that human experimental migraine provocation compounds, such as nitroglycerin (NTG) and pituitary adenylate cyclase activating polypeptide (PACAP), can trigger typical premonitory symptoms (PS) and migraine-like headache in patients with migraine, have allowed feasible and reproducible imaging of the premonitory phase using NTG. Some studies have used serial scanning of patients with migraine to image the migraine cycle, including the 'pre-ictal' phase, defined by timing to headache onset rather than symptom phenotype. Direct observation and functional neuroimaging of triggered PS have also revealed compatible neural substrates for PS in the absence of headache. Various imaging methods including resting state functional MRI (rsfMRI), arterial spin labelling (ASL), positron emission tomography (PET) and diffusion tensor imaging (DTI) have been used. The results of imaging the spontaneous and triggered premonitory phase have been largely consistent and support a theory of central migraine attack initiation involving brain areas such as the hypothalamus, midbrain and limbic system. Early dysfunctional pain, sensory, limbic and homeostatic processing via monoaminergic and peptidergic neurotransmission likely manifests in the heterogeneous PS phenotype.

CONCLUSION

Advances in human migraine research, including the use of functional imaging techniques lacking radiation or radio-isotope exposure, have led to an exciting opportunity to study the premonitory phase using repeated measures imaging designs. These studies have provided novel insights into attack initiation, migraine neurochemistry and therapeutic targets. Emerging migraine-specific therapies, such as those targeting calcitonin gene-related peptide (CGRP), are showing promise acutely when taken during premonitory phase to reduce symptoms and prevent subsequent headache. Therapeutic research in this area using PS for headache onset prediction and early treatment is likely to grow in the future.

Metabolism of sumatriptan revisited

Scientific literature describes that sumatriptan is metabolized by oxidative deamination of its dimethylaminoethyl residue by monoamine oxidase A (MAO A) and not by cytochrome P450 (CYP)-mediated demethylation, as is usual for such structural elements. Using recombinant human enzymes and HPLC-MS analysis, we found that CYP enzymes may also be involved in the metabolism of sumatriptan. The CYP1A2, CYP2C19, and CYP2D6 isoforms converted this drug into N-desmethyl sumatriptan, which was further demethylated to N,N-didesmethyl sumatriptan by CYP1A2 and CYP2D6. Otherwise, sumatriptan and its two desmethyl metabolites were metabolized by recombinant MAO A but not by MAO B to the corresponding acetaldehyde, with sumatriptan being only a poor substrate for MAO A compared to the N-demethylated and the N,N-didemethylated derivatives.

Progress in the Treatment of Migraine Attacks: From Traditional Approaches to Eptinezumab

Migraine is the second cause of disability and of lost years of healthy life worldwide. Migraine is characterized by recurrent headache attacks and accompanying disabling symptoms lasting 4–48 h. In episodic migraine, attacks occur in less than 15 days per month and in chronic migraine, in more than 15 monthly days. Whilst successful translation of pharmacological discoveries into efficacious therapeutics has been achieved in the preventative therapy of chronic migraine, treatment of acute migraine suffers the lack of effective advancements. An effective treatment affords complete freedom from pain two hours after therapy and provides the absence of the most bothersome symptom (MBS) associated with migraine after 2 h. However, available anti-migraine abortive treatments for acute attacks do not represent an effective and safe treatment for all the populations treated. In particular, the most used specific treatment is represented by triptans that offer 2-h sustained freedom from pain achieved in 18–50% of patients but they are contraindicated in coronary artery disease, stroke and peripheral vascular disease due to the vasoconstriction at the basis of their pharmacologic action. The most novel therapies, i.e., gepants and ditans, are without sufficient post-marketing data for secure use. Here, an attempt is proposed to analyse the rational basis and evidence in favour of investigating the efficacy and safety in acute migraine attacks of eptinezumab, i.e., monoclonal antibody (mAb) directed towards calcitonin gene-related peptide (CGRP) unique for intravenous infusion administration.

Genetics, pathophysiology, diagnosis, treatment, management, and prevention of migraine

Migraine is a neurological ailment that is characterized by severe throbbing unilateral headache and associated with nausea, photophobia, phonophobia and vomiting. A full and clear mechanism of the pathogenesis of migraine, though studied extensively, has not been established yet. The current available information indicates an intracranial network activation that culminates in the sensitization of the trigemino-vascular system, release of inflammatory markers, and initiation of meningeal-like inflammatory reaction that is sensed as headache. Genetic factors might play a significant role in deciding an individual's susceptibility to migraine. Twin studies have revealed that a single gene polymorphism can lead to migraine in individuals with a monogenic migraine disorder. In this review, we describe recent advancements in the genetics, pathophysiology, diagnosis, treatment, management, and prevention of migraine. We also discuss the potential roles of genetic and abnormal factors, including some of the metabolic triggering factors that result in migraine attacks. This review will help to accumulate current knowledge about migraine and understanding of its pathophysiology, and provides up-to-date prevention strategies.

Pharmacokinetics of Organic Cation Transporter 1 (OCT1) Substrates in Oct1/2 Knockout Mice and Species Difference in Hepatic OCT1-Mediated Uptake

Organic cation transporter 1 (OCT1) plays a role in hepatic uptake of drugs, affecting in vivo exposure, distinguished primarily through pharmacogenetics of the SLC22A1 gene. The role of OCT1 in vivo has not been confirmed, however, via drug-drug interactions that similarly affect exposure. In the current research, we used Oct1/2 knockout mice to assess the role of Oct1 in hepatic clearance and liver partitioning of clinical substrates and assess the model for predicting an effect of OCT1 function on pharmacokinetics in humans. Four OCT1 substrates (sumatriptan, fenoterol, ondansetron, and tropisetron) were administered to wild-type and knockout mice, and plasma, tissue, and urine were collected. Tissue transporter expression was evaluated using liquid chromatography-mass spectrometry. In vitro, uptake of all compounds in human and mouse hepatocytes and human OCT1- and OCT2-expressing cells was evaluated. The largest effect of knockout was on hepatic clearance and liver partitioning of sumatriptan (2- to 5-fold change), followed by fenoterol, whereas minimal changes in the pharmacokinetics of ondansetron and tropisetron were observed. This aligned with uptake in mouse hepatocytes, in which inhibition of uptake of sumatriptan and fenoterol into mouse hepatocytes by an OCT1 inhibitor was much greater compared with ondansetron and tropisetron. Conversely, inhibition of all four substrates was evident in human hepatocytes, in line with reported clinical pharmacogenetic data. These data confirm the role of Oct1 in the hepatic uptake of the four OCT1 substrates and elucidate species differences in OCT1-mediated hepatocyte uptake that should be considered when utilizing the model to predict effects in humans. SIGNIFICANCE STATEMENT: Studies in carriers of SLC22A1 null variants indicate a role of organic cation transporter 1 (OCT1) in the hepatic uptake of therapeutic agents, although OCT1-mediated drug-drug interactions have not been reported. This work used Oct1/2 knockout mice to confirm the role of Oct1 in the hepatic clearance and liver partitioning in mice for OCT1 substrates with reported pharmacogenetic effects. Species differences observed in mouse and human hepatocyte uptake clarify limitations of the knockout model for predicting exposure changes in humans for some OCT1 substrates.

A systematic review of rescue analgesic strategies in acute exacerbations of primary trigeminal neuralgia

BACKGROUND

Trigeminal neuralgia (TN) can have a significant impact on wellbeing and quality of life. Limited data exist for treatments that improve TN pain acutely, within 24 h of administration. This systematic review aims to identify effective treatments that acutely relieve TN exacerbations.

METHODS

We searched Medline and Cochrane Central Register of Controlled Trials (CENTRAL) for relevant English language publications. The reference list for all articles was searched for other relevant publications. All studies that satisfied the following PICO criteria were included: (i) Population-adults with acute exacerbation of primary TN symptoms; (ii) Intervention-any medication or intervention with the primary goal of pain relief within 24 h; (iii) Comparator-usual medical care, placebo, sham or active treatment; (iv) Outcome-more than 50% reduction in pain intensity within 24 h of administration.

RESULTS

Of 431 studies, 17 studies were identified that reported immediate results of acute treatment in TN. The evidence suggests that the following interventions may be beneficial: local anaesthetic, mainly lidocaine (ophthalmic, nasal or oral mucosa, trigger point injection, i.v. infusion, nerve block); anticonvulsant, phenytoin or fosphenytoin (i.v. infusion); serotonin agonist, sumatriptan (s.c. injection, nasal). Other referenced interventions with very limited evidence include N-methyl-d-aspartate receptor antagonist (magnesium sulphate infusion) and botulinum toxin (trigger point injection).

CONCLUSIONS

Several treatment options exist that may provide fast and safe relief of TN. Future studies should report on outcomes within 24 h to improve knowledge of the acute analgesic TN treatments.

Is selective 5-HT1F receptor agonism an entity apart from that of the triptans in antimigraine therapy?

Migraine is a neurovascular disorder that involves activation of the trigeminovascular system and cranial vasodilation mediated by release of calcitonin gene-related peptide (CGRP). The gold standard for acute migraine treatment are the triptans, 5-HT1B/1D/(1F) receptor agonists. Their actions are thought to be mediated through activation of: (i) 5-HT1B receptors in cranial blood vessels with subsequent cranial vasoconstriction; (ii) prejunctional 5-HT1D receptors on trigeminal fibers that inhibit trigeminal CGRP release; and (iii) 5-HT1B/1D/1F receptors in central nervous system involved in (anti)nociceptive modulation. Unfortunately, coronary arteries also express 5-HT1B receptors whose activation would produce coronary vasoconstriction; hence, triptans are contraindicated in patients with cardiovascular disease. In addition, since migraineurs have an increased cardiovascular risk, it is important to develop antimigraine drugs devoid of vascular (side) effects. Ditans, here defined as selective 5-HT1F receptor agonists, were developed on the basis that most of the triptans activate trigeminal 5-HT1F receptors, which may explain part of the triptans' antimigraine action. Amongst the ditans, lasmiditan: (i) fails to constrict human coronary arteries; and (ii) is effective for the acute treatment of migraine in preliminary Phase III clinical trials. Admittedly, the exact site of action is still unknown, but lasmiditan possess a high lipophilicity, which suggests a direct action on the central descending antinociceptive pathways. Furthermore, since 5-HT1F receptors are located on trigeminal fibers, they could modulate CGRP release. This review will be particularly focussed on the similarities and differences between the triptans and the ditans, their proposed sites of action, side effects and their cardiovascular risk profile.

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.

Vasoreactivity of the Intracranial Internal Carotid Artery

The vasoreactivity of the intracranial segment of the internal carotid artery to transmitters, present in the perivascular sympathetic, parasympathetic and sensory nerves, as well as to other vasoactive agents of relevance for headache, was tested in man and monkey. The total arterial segment from both species is equipped with contractile receptors for noradrenaline, serotonin, prostaglandin F2a, ergotamine and sumatriptan. Further, the total arterial segment dilated upon exposure to calcitonin gene-related peptide in both species. Other vascoactive transmitters, acetylcholine, substance P and neurokinin A, caused only weak dilatation, restricted to the proximal extracavernous segment in the monkey. The findings are discussed in relation to the pathogenesis and treatment of cluster headache.

Comparison of Rizatriptan 5 mg and 10 mg Tablets and Sumatriptan 25 mg and 50 mg Tablets

This randomized, double-blind, two-attack, placebo-controlled, crossover study explored the efficacy and tolerability of rizatriptan 10 mg compared with sumatriptan 50 mg as well as rizatriptan 5 mg compared with sumatriptan 25 mg in the acute treatment of migraine. Following randomization to one of six possible treatment sequences, patients ( n = 1447) treated two sequential attacks, of moderate or severe intensity, separated by at least 5 days. Patients assessed pain severity, migraine-associated symptoms, and functional disability at 0.5, 1, 1.5, and 2 h post treatment. Compared with placebo, all treatments were effective. On the primary endpoint of time to pain relief, rizatriptan 10 mg was not statistically different from sumatriptan 50 mg [odds ratio (OR) 1.10, P = 0.161], and rizatriptan 5 mg was statistically superior to sumatriptan 25 mg (OR 1.22, P = 0.007). In general, rizatriptan 10 mg and 5 mg treatment resulted in improvement compared with the corresponding doses of sumatriptan on measures of pain severity, migraine symptoms, and functional disability and the 5-mg dose reached statistical significance on almost all measures. All treatments were generally well tolerated.

Migraine in the era of precision medicine

Migraine is a common neurovascular disorder in the neurologic clinics whose mechanisms have been explored for several years. The aura has been considered to be attributed to cortical spreading depression (CSD) and dysfunction of the trigeminovascular system is the key factor that has been considered in the pathogenesis of migraine pain. Moreover, three genes (CACNA1A, ATP1A2, and SCN1A) have come from studies performed in individuals with familial hemiplegic migraine (FHM), a monogenic form of migraine with aura. Therapies targeting on the neuropeptids and genes may be helpful in the precision medicine of migraineurs. 5-hydroxytryptamine (5-HT) receptor agonists and calcitonin gene-related peptide (CGRP) receptor antagonists have demonstrated efficacy in the acute specific treatment of migraine attacks. Therefore, ongoing and future efforts to find new vulnerabilities of migraine, unravel the complexity of drug therapy, and perform biomarker-driven clinical trials are necessary to improve outcomes for patients with migraine.

Calcitonin Gene-Related Peptide Modulates Heat Nociception in the Human Brain - An fMRI Study in Healthy Volunteers

Background

Intravenous infusion of calcitonin-gene-related-peptide (CGRP) provokes headache and migraine in humans. Mechanisms underlying CGRP-induced headache are not fully clarified and it is unknown to what extent CGRP modulates nociceptive processing in the brain. To elucidate this we recorded blood-oxygenation-level-dependent (BOLD) signals in the brain by functional MRI after infusion of CGRP in a double-blind placebo-controlled crossover study of 27 healthy volunteers. BOLD-signals were recorded in response to noxious heat stimuli in the V1-area of the trigeminal nerve. In addition, we measured BOLD-signals after injection of sumatriptan (5-HT_1B/1D antagonist).

Results

Brain activation to noxious heat stimuli following CGRP infusion compared to baseline resulted in increased BOLD-signal in insula and brainstem, and decreased BOLD-signal in the caudate nuclei, thalamus and cingulate cortex. Sumatriptan injection reversed these changes.

Conclusion

The changes in BOLD-signals in the brain after CGRP infusion suggests that systemic CGRP modulates nociceptive transmission in the trigeminal pain pathways in response to noxious heat stimuli.

OCT1 mediates hepatic uptake of sumatriptan and loss-of-function OCT1 polymorphisms affect sumatriptan pharmacokinetics

The low bioavailability of the anti-migraine drug sumatriptan is partially caused by first-pass hepatic metabolism. In this study, we analyzed the impact of the hepatic organic cation transporter OCT1 on sumatriptan cellular uptake, and of OCT1 polymorphisms on sumatriptan pharmacokinetics. OCT1 transported sumatriptan with high capacity and sumatriptan uptake into human hepatocytes was strongly inhibited by the OCT1 inhibitor MPP(+) . Sumatriptan uptake was not affected by the Met420del polymorphism, but was strongly reduced by Arg61Cys and Gly401Ser, and completely abolished by Gly465Arg and Cys88Arg. Plasma concentrations in humans with two deficient OCT1 alleles were 215% of those with fully active OCT1 (P = 0.0003). OCT1 also transported naratriptan, rizatriptan, and zolmitriptan, suggesting a possible impact of OCT1 polymorphisms on the pharmacokinetics of other triptans as well. In conclusion, OCT1 is a high-capacity transporter of sumatriptan and polymorphisms causing OCT1 deficiency have similar effects on sumatriptan pharmacokinetics as those observed in subjects with liver impairment.

Anti-migraine effect of Areca Catechu L. nut extract in bradykinin-induced plasma protein extravasation and vocalization in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Areca catechu Linn. (Arecaceae) nut is a popular folk remedy for the treatment of migraine in Kerala and Tamil Nadu states of India.

AIM OF THE STUDY

This study was designed to investigate the effect of hydroalcoholic extract of A. catechu L. nut (ANE) treatment on migraine pain in rat models to strengthen its use as an anti-migraine therapy.

MATERIALS AND METHODS

Bradykinin (0.1 μmol/kg) injection in to left femoral vein of rat produced PPE which was measured with luminescence spectrometer. Vocalizations were produced in rats with 10 μg of bradykinin infusion into common carotid artery. Phonogram was recorded before, during and for 5min after bradykinin injection and sumatriptan was used as a standard anti-migraine drug. In both models, the ANE was orally administered at doses of 250 and 500 mg/kg, 60 min before bradykinin infusion.

RESULTS

The PPE was reduced in both ANE treated groups of rats. The percent fluorescein was significantly increased in positive control group (97.00±1.7%; p<0.0001) compared to negative control (63.87±1.2%). With ANE treatments (250 and 500 mg/kg) PPE was significantly decreased to 88.88±1.4% (p<0.01) and 83.55±0.1% (p<0.0001) compared to positive control group, respectively. On the other hand in the model of vocalization, with 250 and 500 mg/kg ANE treatment, vocalization was significantly reduced to 33.33% and 16.66%, respectively, compared to saline treated rats. The reduction in vocalization is comparable to the reference drug sumatriptan.

CONCLUSION

The findings provide the strong evidence for anti-migraine potential of ANE in rat models of migraine. In summary, therapeutic intervention with ANE treatment could be a promising strategy for prevention of migraine.

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.

Microdosing and drug development: past, present and future

INTRODUCTION

Microdosing is an approach to early drug development where exploratory pharmacokinetic data are acquired in humans using inherently safe sub-pharmacologic doses of drug. The first publication of microdose data was 10 years ago and this review comprehensively explores the microdose concept from conception, over the past decade, up until the current date.

AREAS COVERED

The authors define and distinguish the concept of microdosing from similar approaches. The authors review the ability of microdosing to provide exploratory pharmacokinetics (concentration-time data) but exclude microdosing using positron emission tomography. The article provides a comprehensive review of data within the peer-reviewed literature as well as the latest applications and a look into the future, towards where microdosing may be headed.

EXPERT OPINION

Evidence so far suggests that microdosing may be a better predictive tool of human pharmacokinetics than alternative methods and combination with physiologically based modelling may lead to much more reliable predictions in the future. The concept has also been applied to drug-drug interactions, polymorphism and assessing drug concentrations over time at its site of action. Microdosing may yet have more to offer in unanticipated directions and provide benefits that have not been fully realised to date.

In Vivo Disintegration Profiles of Encapsulated and Nonencapsulated Sumatriptan: Gamma Scintigraphy in Healthy Volunteers

The goal of this exploratory pilot study was to use gamma scintigraphy to evaluate, under physiological conditions, disintegration profiles of encapsulated and nonencapsulated formulations of 100 mg sumatriptan. Using a crossover design, healthy volunteers (n = 10) ingested 100-mg doses of sumatriptan tablets radiolabeled with 111Indium, as well as encapsulated sumatriptan tablets that were prepared similarly, then placed within a gelatin capsule and backfilled with an excipient blend radiolabeled with 99mTechnetium. A gamma camera recorded scintigraphic images until 5 hours postdose. Initial disintegration of the gelatin capsule was observed at a mean (range) of 5 minutes (1-11 minutes); disintegration was complete within 14 minutes (5-24 minutes). For nonencapsulated versus encapsulated tablets, the mean (+/- standard deviation) time to initial disintegration (6 +/- 5 minutes vs 8 +/- 5 minutes) and time to complete disintegration (18 +/- 14 minutes vs 16 +/- 7 minutes) were comparable. Results of this study demonstrate that encapsulated and nonencapsulated sumatriptan have equivalent in vivo dissolution rates.

Epigallocatechin gallate, cerebral blood flow parameters, cognitive performance and mood in healthy humans: a double-blind, placebo-controlled, crossover investigation

OBJECTIVE

The aim of the study was to assess the effects of oral ingestion of the 'green tea' polyphenol epigallocatechin gallate (EGCG) on cognitive performance, mood and localised cerebral blood flow (CBF) parameters in healthy human adults.

METHOD

In this double-blind, placebo-controlled, crossover study, 27 healthy adults received placebo and two doses (135 and 270 mg) of EGCG in counterbalanced order on separate days. Following a 45-min resting absorption period, participants performed a selection of computerised cognitive tasks that activate the frontal cortex for a further 42 min. CBF and haemodynamics, as indexed by concentration changes in oxygenated and deoxygenated haemoglobin, were assessed in the frontal cortex throughout the post-treatment period using Near-infrared spectroscopy (NIRS).

RESULTS

During the post-dose task performance period, the administration of 135 mg EGCG resulted in reduced CBF in the frontal cortex, as indexed by significantly lower concentrations of both oxygenated and total haemoglobin, in comparison with placebo. Heart rate was significantly reduced from pre dose to post dose across all treatments. No significant differences were observed for the level of deoxygenated haemoglobin or on any of the cognitive performance/mood measures.

CONCLUSIONS

These results demonstrate that a single dose of orally administered EGCG can modulate CBF parameters in healthy humans but that this is not associated with changes in cognitive performance or mood.

Why pharmacokinetic differences among oral triptans have little clinical importance: a comment

Triptans, selective 5-HT1B/1D receptor agonists, are specific drugs for the acute treatment of migraine that have the same mechanism of action. Here, it is discussed why the differences among kinetic parameters of oral triptans have proved not to be very important in clinical practice. There are three main reasons: (1) the differences among the kinetic parameters of oral triptans are smaller than what appears from their average values; (2) there is a large inter-subject, gender-dependent, and intra-subject (outside/during the attack) variability of kinetic parameters related to the rate and extent of absorption, i.e., those which are considered as critical for the response; (3) no dose-concentration–response curves have been defined and it is, therefore, impossible both to compare the kinetics of triptans, and to verify the objective importance of kinetic differences; (4) the importance of kinetic differences is outweighed by non-kinetic factors of variability of response to triptans. If no oral formulations are found that can allow more predictable pharmacokinetics, the same problems will probably also arise with new classes of drugs for the acute treatment of migraine.

Sumatriptan-naproxen fixed combination for acute treatment of migraine: a critical appraisal

Nonsteroidal anti-inflammatory drugs (NSAIDs), including naproxen and naproxen sodium, are effective yet nonspecific analgesic and anti-inflammatory drugs, which work for a variety of pain and inflammatory syndromes, including migraine. In migraine, their analgesic effect helps relieve the headache, while their anti-inflammatory effect decreases the neurogenic inflammation in the trigeminal ganglion. This is the hypothesized mechanism by which they prevent the development of central sensitization. Triptans, including sumatriptan, work early in the migraine process at the trigeminovascular unit as agonists of the serotonin receptors (5-HT receptors) 1B and 1D. They block vasoconstriction and block transmission of signals to the trigeminal nucleus and thus prevent peripheral sensitization. Therefore, combining these two drugs is an attractive modality for the abortive treatment of migraine. Sumatriptan-naproxen fixed combination tablet (Treximet [sumatriptan-naproxen]) proves to be an effective and well tolerated drug that combines these two mechanisms; yet is far from being the ultimate in migraine abortive therapy, and further research remains essential.

Amine oxidases and monooxygenases in the in vivo metabolism of xenobiotic amines in humans: has the involvement of amine oxidases been neglected?

In this review, the major enzyme systems involved in vivo in the oxidative metabolism of xenobiotic amines in humans are discussed, i.e. the monooxygenases [cytochrome P450 system (CYPs) and flavin-containing monooxygenases (FMOs)] and the amine oxidases (AOs). Concerning the metabolism of xenobiotic amines (drugs in particular) by monoamine oxidases (MAOs), this aspect has been largely neglected in the past. An exception is the extensive investigation carried out on the inhibition of the metabolism of tyramine, when tyramine-containing food is ingested by subjects taking inhibitors of MAO A or of both MAO A and B. Moreover, investigations in humans on the metabolism of drug amines on the market by AOs, such as semicarbazide-sensitive amine oxidases (SSAOs) and polyamine oxidases (PAOs), are practically nonexistent, with the exception of amlodipine. In contrast to MAOs, monooxygenases (CYP isoenzymes more than FMOs) have been extensively investigated concerning their involvement in the metabolism of xenobiotics. It is possible that the contribution of AOs to the overall metabolism of xenobiotic amines in humans is underestimated or erroneously estimated, as most investigations of drug metabolism are performed using in vitro test systems optimized for CYP activity, such as liver microsomes, and most investigations of drug metabolism in vivo in humans carry out only the identification of the final, stable metabolites. However, for some drugs on the market, the involvement of MAOs in their in vivo metabolism in humans has been demonstrated recently, among these drugs citalopram, sertraline and the triptans are examples that can be mentioned.

Nasal delivery of antimigraine drugs: clinical rationale and evidence base

The intranasal route of administration for antimigraine drugs offers many theoretical and practical advantages. A drug that is administered intranasally is absorbed by the highly vascular mucous membranes of the nose, which allows for rapid delivery of un-metabolized drug to the central nervous system. The onset of action is thus considerably earlier than with oral administration requiring gastrointestinal absorption. The intranasal route also provides several practical advantages, such as greater acceptability to patients because of the noninvasive mode of delivery, the ability to take medication when severe nausea or vomiting is present, and a better adverse event profile. Three antimigraine drugs are available in intranasal formulation: dihydroergotamine, sumatriptan, and zolmitriptan. This article reviews the pharmacology, efficacy, safety, and tolerability of these agents. All are well tolerated by patients and have demonstrated efficacy in the treatment of migraine headache. Each of these drugs has a unique pharmacokinetic and pharmacodynamic profile, which may support a clinical preference for one intranasal agent over another in treating patients with specific headache features.

Sumatriptan: update and review

Sumatriptan is the first of a novel class of medications referred to as triptans. Since its approval for migraine in the 1990s, six other triptan products have received FDA approval. Despite the proliferation of triptans, sumatriptan remains the most frequently prescribed product in this therapeutic class. Sumatriptan has been instrumental in defining a biological basis for migraine. It is effective in treating migraine with or without aura, well tolerated and, when properly prescribed, safe. Sumatriptan injection is the only member of the triptan class approved for treatment of cluster headache. Studies with sumatriptan have also advanced the therapeutic intervention paradigm that permits patients to treat earlier and avoid substantial disability. Numerous pharmacoeconomic studies have demonstrated that sumatriptan decreases work loss productivity and improves quality of life.

Sumatriptan alleviates pain in patients with trigeminal neuralgia

OBJECTIVES

Arterial compression of the trigeminal root may lead to trigeminal neuralgia. 5-HT1B/1D receptor agonists may inhibit vasodilation and inflammation near the irritated trigeminal root. A recent study showed attenuation of mechanical allodynia by a 5-HT1A receptor agonist in a rat model of trigeminal neuralgia. The present study examined the effectiveness of a 5-HT1A/1B/1D receptor agonist, sumatriptan, on pain relief in patients with trigeminal neuralgia.

METHODS

The study was conducted in 15 patients with idiopathic trigeminal neuralgia. The patients had been suffering from painful paroxysms for at least 1 month. Each patient was injected with 1 mL of saline subcutaneously (placebo), followed 15 minutes later with subcutaneous sumatriptan (3 mg in 1 mL saline). This was followed the next day by oral sumatriptan (50 mg twice daily) for 1 week.

RESULTS

The visual analog scale did not change after saline, but significantly decreased after subcutaneous sumatriptan. Both 1 week after oral sumatriptan and 1 week after discontinuation of the drug, visual analog scale scores resulted in a significant decrease from the baseline. Adverse events after subcutaneous sumatriptan occurred in 4 patients: fatigue in 4 and nausea in 2. Side effects from the oral medication appeared in 4 patients: fatigue in 2, nausea in 1 and chest discomfort in 1. These side effects subsided soon after discontinuation of sumatriptan.

CONCLUSIONS

Our results indicate that subcutaneous injection followed by oral administration of sumatriptan produces prompt and continuous analgesia in patients with trigeminal neuralgia.

Subcutaneous sumatriptan for refractory trigeminal neuralgia

BACKGROUND

Mechanical compression of the trigeminal root by an artery is thought to cause trigeminal neuralgia. The 5-HT(1B/1D) receptor agonist may inhibit neurogenic inflammation and vasodilation near the irritated trigeminal root.

OBJECTIVE

To examine the effectiveness of a 5-HT(1B/1D) receptor agonist, sumatriptan, on a paroxysmal pain in trigeminal neuralgia.

METHODS

Twenty-four patients with trigeminal neuralgia refractory to previous treatment were randomized to receive subcutaneously either 3 mg (1 mL) of sumatriptan or 1 mL of saline placebo. Following a 7-day period, patients crossed over to receive the alternative treatment. Paroxysmal pain triggered by touching or moving the face was assessed with VAS before and 15 minutes after the treatment. Patients used a descriptive scale to pain-grade outcome, and asked to note whether the pain returned and how long after therapy it recurred.

RESULTS

Subcutaneous sumatriptan, but not placebo, significantly decreased VAS from 8.3 +/- 2.1 to 2.4 +/- 3.0 cm (mean +/- SD). The number of patients who described their pain as moderately or slightly better was 20 in the sumatriptan group and 1 in the placebo group. The effect of subcutaneous sumatriptan persisted for a median period of 7.9 hours (range: 1-20 hours).

CONCLUSIONS

Subcutaneous sumatriptan produced prompt analgesia without serious adverse reactions in patients with trigeminal neuralgia refractory to previous treatment.

Thermoreversible-mucoadhesive gel for nasal delivery of sumatriptan

The purpose of the present study was to develop intranasal delivery systems of sumatriptan using thermoreversible polymer Pluronic F127 (PF127) and mucoadhesive polymer Carbopol 934P (C934P). Formulations were modulated so as to have gelation temperature below 34 degrees C to ensure gelation at physiological temperature after intranasal administration. Gelation temperature was determined by physical appearance as well as by rheological measurement. The gelation temperatures of the formulations decreased by addition of increasing concentrations of Carbopol (ie, from 29 degrees C for 18% PF127 to 23.9 degrees C for 18% PF127, 0.5% Carbopol). The mucoadhesive force in terms of detachment stress, determined using sheep nasal mucosal membrane, increased with increasing concentration of Carbopol. The results of in vitro drug permeation studies across sheep nasal mucosa indicate that effective permeation coefficient could be significantly increased by using in situ gelling formulation with Carbopol concentration 0.3% or greater. Finally, histopathological examination did not detect any damage during in vitro permeation studies. In conclusion, the PF127 gel formulation of sumatriptan with in situ gelling and mucoadhesive properties with increased permeation rate is promising for prolonging nasal residence time and thereby nasal absorption.

Sumatriptan: a decade of use and experience in the treatment of migraine

The migraine-specific triptans have revolutionized the treatment of migraine and are usually the drugs of choice to treat a migraine attack in progress. Sumatriptan (Imitrex) has been available for the longest time within the class, is most flexible in form and has been given successfully to the most number of patients. It is useful for the full range of attacks experienced by a migraine suffer. The aim of this review is to provide an overview of the first 10 years of the use of sumatriptan.

Zolmitriptan Intranasal: A Review of the Pharmacokinetics and Clinical Efficacy

Migraine is a common disabling neurological disorder, associated with headache, nausea, and on occasions vomiting. Zolmitriptan is a widely available serotonin 5HT(1B/1D) receptor agonist with a long track record in clinical studies and in the treatment of acute migraine. A nasal formulation has been developed that has clear evidence for local absorption, resulting in plasma drug concentrations within 2 minutes of dosing, central nervous system penetration 3 minutes later, and a significant efficacy benefit versus placebo 10 to 15 minutes after dosing. Intranasal zolmitriptan offers advantages to migraineurs, particularly those seeking a more rapid onset of effect without wishing to self-inject, or those with gastrointestinal upset. The comparison of pharmacokinetic and clinical data available from different formulations of zolmitriptan contributes both to the understanding of its mode of action and the characteristics required of an acute migraine treatment if it is to meet patient needs.

Triptan-induced contractile (5-HT1B receptor) responses in human cerebral and coronary arteries: relationship to clinical effect

Triptans are agonists at 5-HT1B and 5-HT1D (where 5-HT is 5-hydroxytryptamine; serotonin) receptors and cause vasoconstriction of isolated blood vessels. The aim of the present study was to determine vasoconstrictor potency (EC50) of triptans in human coronary and cerebral arteries and to examine whether there was any relationship with the maximal plasma concentrations (Cmax; nM) of the drugs achieved following oral administration of clinically relevant doses to man using values reported in the literature. We also examined the expression of 5-HT1B receptors in atherosclerotic and normal coronary arteries. The vasocontractile responses to sumatriptan, rizatriptan or eletriptan were characterized by in vitro pharmacology. The ratio of Cmax/EC50 was calculated. 5-HT1B and 5-HT1D receptors were visualized by immunohistochemical techniques in coronary arteries. Sumatriptan, rizatriptan and eletriptan were powerful vasoconstrictors in cerebral artery. The rank order of agonist potency was eletriptan=rizatriptan=sumatriptan. In the coronary artery, the triptans were weaker vasoconstrictors. The rank order of potency was similar. In cerebral artery the ratio of Cmax/EC50 was not significantly different from unity, indicating a relationship between these two parameters. In general for the coronary artery, the ratios were significantly less than unity, indicating no direct relationship. Immunohistochemistry showed expression of 5-HT1B receptors in the medial layer, but did not reveal any obvious difference in 5-HT1B receptor expression between normal and atherosclerotic coronary arteries. The results support the notion that triptans are selective vasoconstrictors of cerebral arteries over coronary arteries and that there is a relationship between vasoconstrictor potency in cerebral arteries and clinically relevant plasma levels.

Pilot Study Evaluating Preference for 3‐mg Versus 6‐mg Subcutaneous Sumatriptan

BACKGROUND

Subcutaneous sumatriptan (6 mg) is undeniably an excellent treatment of migraine. However, some patients have avoided using 6 mg sumatriptan because of unpleasant or unwanted side effects.

OBJECTIVE

To evaluate the efficacy of subcutaneous sumatriptan (3 mg) during a moderate or severe migraine attack.

METHODS

Thirty subcutaneous sumatriptan-naive patients with a history of migraine with and without aura treated their next two moderate or severe migraines with either 3-mg or 6-mg sumatriptan injection. The primary endpoint was whether patients preferred the low-dose (3 mg) or the high-dose (6 mg) subcutaneous sumatriptan. Other objectives included percentage of patients pain free at 15 and 30 minutes, 1 and 2 hours; a pain-free response lasting between 2 and 24 hours, patient satisfaction, and acceptability of formulation. A new combination endpoint (efficacy and lack of significant side effects) was also evaluated.

RESULTS

Eighty percent of patients preferred 3-mg over 6-mg subcutaneous sumatriptan. At 1 hour postdose 57% of patients were pain free with 3 mg and 53% with 6 mg. At 2 hours postdose 87% were pain free with 3 mg and 80% with 6 mg. A sustained pain-free response was obtained by 70 to 80% of patients. When combining a pain-free response at 2 hours and a sustained pain-free response at 24 hours with no significant side effects, more patients met the endpoint with 3 mg (63 to 67%) than with 6 mg (33 to 50%).

CONCLUSIONS

Combining efficacy and tolerability endpoints may be clinically meaningful and reflective of real-world expectations. In some patients, a lower dose of sumatriptan injection may be beneficial.

Evaluating the triptans

The debilitating effect of migraine has fueled the search for more specific agents to treat its characteristic and associated symptoms. Second-generation oral triptans have shown an improved efficacy profile in comparison with the pioneer sumatriptan and with the over-the-counter medications and prescription analgesics that have been staples of migraine treatment. Although all triptans exert effects through the 5-hydroxytryptamine 1B/1D receptors, each triptan has distinctive pharmacokinetic properties that determine its efficacy and tolerability profile. Empirical findings based on clinical trials have led to associations between triptan pharmacology and efficacy. With the expanded treatment choices, the onus is on healthcare providers (especially primary care physicians, who see the majority of patients with migraine) to determine which treatment has an efficacy profile that best suits the individual patient's needs. Patients prefer pharmacotherapy with a rapid onset of action that facilitates complete pain relief and no recurrence. Data from published comparator trials, based on commonly used efficacy end points and pharmacokinetic properties underlying patient-preferred outcomes, are reviewed in this article.