Effects of the novel high-affinity 5-HT(1B/1D)-receptor ligand frovatriptan in human isolated basilar and coronary arteries

Lasmiditan for Patients with Migraine and Contraindications to Triptans: A Post Hoc Analysis

INTRODUCTION

As 5-HT1B receptor agonists, triptans produce vasoconstriction and have cardiovascular contraindications and precautions. Lasmiditan, a selective 5-HT1F receptor agonist, has a low affinity for 5-HT1B receptors, does not cause vasoconstriction, and is free of cardiovascular contraindications and precautions. The objective of this post hoc analysis was to evaluate the efficacy and safety of lasmiditan in patients with and without at least one triptan contraindication.

METHODS

Patient subgroups, with and without triptan contraindications, were analyzed from pooled patient data from four randomized, double-blind, placebo-controlled clinical trials (SAMURAI, SPARTAN, CENTURION, and MONONOFU). Patients experiencing a single migraine attack of moderate or severe intensity were treated with lasmiditan 50 mg (SPARTAN and MONONOFU only), 100 mg, 200 mg, or placebo, and efficacy data were recorded in an electronic diary.

RESULTS

Of 5704 patients, 207 (3.6%) patients had at least one contraindication to triptans. Overall subgroup analysis revealed that the effects of lasmiditan on pain freedom, pain relief, freedom from most bothersome symptom, disability freedom, and Patient Global Impression of Change at 2 h post-dose did not differ in patient groups with and without triptan contraindications. These outcomes generally showed a similar benefit pattern for lasmiditan in both subgroups, with all results being statistically significant in patients without contraindications, and pain relief being statistically significant in patients with contraindications. The safety and tolerability profiles of patients with triptan versus without triptan contraindications were similar, including dizziness in 18.3 to 22.8% and somnolence in 7.9 to 9.9% of patients at the highest dose of lasmiditan.

CONCLUSIONS

In pooled analyses from four trials, patients with and without triptan contraindications did not differ in their patterns of lasmiditan efficacy. Lasmiditan may be a treatment option in patients with contraindications to triptans.

TRIAL REGISTRATION NUMBERS

SAMURAI, NCT:02439320; SPARTAN, NCT:02605174; CENTURION, NCT:03670810; and MONONOFU, NCT:03962738.

Characterization of binding, functional activity, and contractile responses of the selective 5-HT1F receptor agonist lasmiditan

BACKGROUND AND PURPOSE

Triptans are 5-HT1B/1D receptor agonists (that also display 5-HT1F receptor affinity) with antimigraine action, contraindicated in patients with coronary artery disease due to their vasoconstrictor properties. Conversely, lasmiditan was developed as an antimigraine 5-HT1F receptor agonist. To assess the selectivity and cardiovascular effects of lasmiditan, we investigated the binding, functional activity, and in vitro/in vivo vascular effects of lasmiditan and compared it to sumatriptan.

EXPERIMENTAL APPROACH

Binding and second messenger activity assays of lasmiditan and other serotoninergic agonists were performed for human 5-HT1A , 5-HT1B , 5-HT1D , 5-ht1E , 5-HT1F , 5-HT2A , 5-HT2B , and 5-HT7 receptors, and the results were correlated with their potency to constrict isolated human coronary arteries (HCAs). Furthermore, concentration-response curves to lasmiditan and sumatriptan were performed in proximal and distal HCA, internal mammary, and middle meningeal arteries. Finally, anaesthetized female beagle dogs received i.v. infusions of lasmiditan or sumatriptan in escalating cumulative doses, and carotid and coronary artery diameters were measured.

KEY RESULTS

Lasmiditan showed high selectivity for 5-HT1F receptors. Moreover, the functional potency of the analysed compounds to inhibit cAMP increase through 5-HT1B receptor activation positively correlated with their potency to contract HCA. In isolated human arteries, sumatriptan, but not lasmiditan, induced contractions. Likewise, in vivo, sumatriptan decreased coronary and carotid artery diameters at clinically relevant doses, while lasmiditan was devoid of vasoconstrictor activity at all doses tested.

CONCLUSIONS AND IMPLICATIONS

Lasmiditan is a selective 5-HT1F receptor agonist devoid of vasoconstrictor activity. This may represent a cardiovascular safety advantage when compared to the triptans.

Effect of High-Dose Intravenous Eletriptan on Coronary Artery Diameter

The goal of this study was to evaluate the coronary vasoconstrictive effects of high doses of eletriptan compared with a standard dose of sumatriptan. Patients with no clinically significant coronary artery disease were randomized to receive high-dose intravenous eletriptan ( n = 24) vs a standard dose of sumatriptan ( n = 18; 6 mg subcutaneously) vs placebo ( n = 18). Serial angiograms were obtained. The primary non-inferiority analysis found equivalence between the mean maximum change in left anterior descending coronary artery diameter for eletriptan, -22% [95% confidence interval (CI) -26, -19], and sumatriptan, -19% (95% CI -22, -16). The change due to placebo was -16% (95% CI -20, -12). No individual cases of clinically significant vasoconstriction were observed. The results confirm that eletriptan has a broad cardiovascular safety margin, with plasma concentrations comparable to three to five times the Cmax of an oral 80-mg dose associated with modest vasoconstriction equivalent to standard therapeutic doses of sumatriptan.

Triptans and Chest Symptoms: The Role of Pulmonary Vasoconstriction

Triptans are effective and well tolerated in the treatment of acute migraine. Chest symptoms are a common adverse effect unrelated to coronary vasoconstriction in most patients. Although the aetiology of chest symptoms remains to be fully defined, pulmonary vasoconstriction is a possible underlying mechanism. Preclinical studies of isolated human blood vessels were used to identify the cerebral selectivity of triptans and ascertain if selectivity vs the pulmonary vasculature predicts a lower rate of chest symptoms. Controlled clinical trials and post-marketing surveillance studies were reviewed to document the incidence of chest symptoms after triptan therapy. In clinical trials, the incidence of chest symptoms at usual therapeutic doses ranged from 1 to 4% depending on the triptan and study design, whereas in post-marketing surveillance studies, up to 41% of patients specifically asked about chest symptoms reported them. A comparative clinical trial showed that almotriptan was associated with lower incidence of chest symptoms than sumatriptan (0.3 vs 2.2%). The intrinsic activity of almotriptan, a second-generation triptan, on human pulmonary arteries and veins was lower than that of sumatriptan. Pre-clinical studies of isolated pulmonary blood vessels may predict the clinical likelihood of chest symptoms; however, additional comparisons are needed.

Managing migraine by patient profile: role of frovatriptan

For the last quarter of a century, triptans have been available for acute treatment of migraine but with little guidance on which of the different triptan products to use for which patient or which attack of migraine. In this article, we propose a structured approach to analysis of individual migraine attacks and patient characteristics as a means of defining and optimizing acute intervention. Assessment of patient and attack profiles includes the "5-Ps": pattern, phenotype, patient, pharmacology, and precipitants. Attending to these five components of information can assist in developing an individualized behavioral, pharmacological, and nonpharmacological comprehensive treatment plan for most migraine patients. This clinical approach is then focused on frovatriptan because of its unique molecular signature and potential novel clinical applications. Frovatriptan like all triptans is indicated for acute treatment of migraine but its role has been explored in management of several unique migraine phenotypes. Frovatriptan has the longest half-life of any triptan and consequently is often promoted for acute treatment of migraine of longer duration. It has also been studied as a short-term preventive treatment in women with menstrual-related migraine. Given that 60% of female migraineurs suffer from menstrual-related migraine, this population is the obvious group for continued study. Small studies have also explored frovatriptan's use in treating migraine predicted by premonitory symptoms as a preventive for the headache phase of migraine. By identifying patient and attack profiles, clinicians may effectively determine the viability of frovatriptan as an effective pharmacological intervention for migraine.

The effect of sumatriptan on cephalic arteries: A 3T MR-angiography study in healthy volunteers

AIM

To explore a possible differential effect of sumatriptan on extracerebral versus cerebral arteries, we examined the superficial temporal (STA), middle meningeal (MMA), extracranial internal carotid (ICAextra), intracranial internal carotid (ICAintra), middle cerebral (MCA) and basilar arteries (BA).

METHODS

The arterial circumferences were recorded blindly using high-resolution magnetic resonance angiography before and after subcutaneous sumatriptan injection (6 mg) in 18 healthy volunteers.

RESULTS

We found significant constrictions of MMA (16.5%), STA (16.4%) and ICAextra (15.2%) ( P  ≤ 0.001). Smaller, but statistically significant, constrictions were seen in MCA (5.5%) and BA (2.1%) ( P  ≤ 0.012). ICAintra change 1.8% was not significant ( P  = 0.179). The constriction of cerebral arteries was significantly smaller than the constriction of extracerebral arteries ( P  < 0.000001).

CONCLUSION

Sumatriptan constricts extracerebral arteries more than cerebral arteries. We suggest that sumatriptan may exert its anti-migraine action outside of the blood-brain barrier.

Frovatriptan salts of aliphatic carboxylic acids

The interaction of the antimigraine pharmaceutical agent frovatriptan with acetic acid and succinic acid yields the salts (±)-6-carbamoyl-N-methyl-2,3,4,9-tetrahydro-1H-carbazol-3-aminium acetate, C14H18N3O(+)·C2H3O2(-), (I), (R)-(+)-6-carbamoyl-N-methyl-2,3,4,9-tetrahydro-1H-carbazol-3-aminium 3-carboxypropanoate monohydrate, C14H18N3O(+)·C4H5O4(-)·H2O, (II), and bis[(R)-(+)-6-carbamoyl-N-methyl-2,3,4,9-tetrahydro-1H-carbazol-3-aminium] succinate trihydrate, 2C14H18N3O(+)·C4H4O4(2-)·3H2O, (III). The methylazaniumyl substitutent is oriented differently in all three structures. Additionally, the amide group in (I) is in a different orientation. All the salts form three-dimensional hydrogen-bonded structures. In (I), the cations form head-to-head hydrogen-bonded amide-amide catemers through N-H···O interactions, while in (II) and (III) the cations form head-to-head amide-amide dimers. The cation catemers in (I) are extended into a three-dimensional network through further interactions with acetate anion acceptors. The presence of succinate anions and water molecules in (II) and (III) primarily governs the three-dimensional network through water-bridged cation-anion associations via O-H···O and N-H···O hydrogen bonds. The structures reported here shed some light on the possible mode of noncovalent interactions in the aggregation and interaction patterns of drug molecule adducts.

Frovatriptan: a review of its use in the acute treatment of migraine

Frovatriptan (Migard®; Frova®) is an orally administered triptan approved for the acute treatment of adults with migraine, with or without aura. This article reviews the pharmacology of frovatriptan, focusing on its efficacy and tolerability. The precise mechanism of action of frovatriptan is unknown, but is thought to stem from agonism at serotonin 5-HT(1B) and 5-HT(1D) receptors, resulting in inhibition of intracranial and extracerebral artery vasodilation, along with possible anti-inflammatory and pain inhibiting effects. Frovatriptan appears to be functionally selective for 5-HT receptors in human basilar arteries over coronary arteries, which could translate into a low cardiovascular risk. In contrast to other triptans, frovatriptan has a long terminal elimination half-life in blood of ≈26 hours, which can be expected to be associated with a sustained treatment effect. Oral frovatriptan 2.5 mg was efficacious in patients with moderate to severe migraine attacks; in randomized, double-blind trials the proportion of patients with headache response at 2 hours (primary endpoint) was consistently significantly higher in frovatriptan than placebo groups. Frovatriptan was generally well tolerated in short-term clinical trials and when used over the longer term. The most frequent treatment-emergent adverse events occurring at a frequency ≥1% higher in frovatriptan than placebo recipients were dizziness, fatigue, headache, paraesthesia, flushing, skeletal pain, hot or cold sensation, dry mouth, chest pain and dyspepsia. In a study in patients with coronary artery disease, or who were at high risk of coronary artery disease, there was no increase over placebo in the occurrence of clinically significant ECG changes or in cardiac rhythm disturbances. In a further trial, frovatriptan administered early in a migraine attack was more efficacious than placebo followed by later administration of frovatriptan as pain progressed. Three crossover trials compared early administration of frovatriptan 2.5 mg with almotriptan 12.5 mg, rizatriptan 10 mg and zolmitriptan 2.5 mg in patients with migraine. There were no significant between-group differences in patient drug preference scores (primary endpoint) or in other endpoints, except for headache recurrence, which favoured frovatriptan in two of the trials. The trials did not test noninferiority of frovatriptan to the comparator. In a placebo-controlled trial that included a sumatriptan active treatment arm, sumatriptan 100 mg was significantly more efficacious than frovatriptan 2.5 mg for this primary endpoint. Frovatriptan was generally better tolerated than all four triptan comparators. In summary, frovatriptan was an efficacious acute treatment for moderate to severe migraine attacks and had a favourable tolerability profile, although in a single trial, it was not as efficacious as sumatriptan. Administration of frovatriptan early in an attack while the attack was at a mild level of intensity was more efficacious than late administration. Furthermore, in clinical trials adopting this early administration strategy, frovatriptan was not significantly less efficacious than almotriptan, rizatriptan and zolmitriptan, appeared to have a more sustained treatment effect, and was better tolerated than the comparators. Frovatriptan provides an alternative treatment for migraine, especially in patients who have had adverse events or frequent headache recurrences with triptans or other antimigraine drugs, and who are amenable to adopting an early administration strategy.

Serotonin and blood pressure regulation

5-Hydroxytryptamine (5-HT; serotonin) was discovered more than 60 years ago as a substance isolated from blood. The neural effects of 5-HT have been well investigated and understood, thanks in part to the pharmacological tools available to dissect the serotonergic system and the development of the frequently prescribed selective serotonin-reuptake inhibitors. By contrast, our understanding of the role of 5-HT in the control and modification of blood pressure pales in comparison. Here we focus on the role of 5-HT in systemic blood pressure control. This review provides an in-depth study of the function and pharmacology of 5-HT in those tissues that can modify blood pressure (blood, vasculature, heart, adrenal gland, kidney, brain), with a focus on the autonomic nervous system that includes mechanisms of action and pharmacology of 5-HT within each system. We compare the change in blood pressure produced in different species by short- and long-term administration of 5-HT or selective serotonin receptor agonists. To further our understanding of the mechanisms through which 5-HT modifies blood pressure, we also describe the blood pressure effects of commonly used drugs that modify the actions of 5-HT. The pharmacology and physiological actions of 5-HT in modifying blood pressure are important, given its involvement in circulatory shock, orthostatic hypotension, serotonin syndrome and hypertension.

Pharmacokinetic evaluation of frovatriptan

INTRODUCTION

Migraine is the most common painful neurological disorder, affecting 13% of the general population. Triptans represent a powerful pharmacological tool in acute migraine treatment, however, a significant portion of treated patients cannot have access to this class due to possible adverse affects. Today, a total of seven triptan molecules are available, representing a commonly prescribed migraine treatment. Although there is a need of extensive use of triptans, only 25% of migraine patients are using triptans.

AREAS COVERED

This review includes triptans and evidence for the use of frovatriptan. A systematic approach is used to discuss the pharmacodynamic and pharmacokinetic aspects of frovatriptan, considering the emerging data on the clinical efficacy of frovatriptan in the treatment of migraine and cluster headaches. The data were obtained by searching the following key words in MEDLINE: pharmacokinetic, pharmacodynamic, triptans, frovatriptan, migraine, menstrual migraine, relatively to the period 1988 - 2011.

EXPERT OPINION

Frovatriptan has been developed in order to improve safety and efficacy of triptans. It shows a favorable tolerability and efficacy profile, limited to 24/48-h headache recurrence, when compared with other triptans. Preclinical data suggest that the pharmacokinetic profile of frovatriptan may differ from other available triptans. In fact, among triptans, frovatriptan showed the highest potency at the 5-HT1B receptor (8.2) and the longer half-life (26 h). These parameters determine the clinical properties of frovatriptan; in particular the lowest rate of headache recurrence in comparison with other triptans.

Frovatriptan: a review of pharmacology, pharmacokinetics and clinical potential in the treatment of menstrual migraine

Frovatriptan is an orally active 5-hydroxytryptamine (5-HT) receptor agonist which binds with high affinity to 5-HT_1B and 5-HT_1D receptors. Earlier clinical trials demonstrated that frovatriptan 2.5 mg is significantly more effective than placebo in the acute management of migraine and its associated symptoms. More recently, frovatriptan was shown to be effective in the management of menstrual migraine. The incidence of menstrual migraine in subjects receiving frovatriptan 2.5 mg twice daily during the six day perimenstrual period was 41% compared with 67% with placebo. Frovatriptan treatment is generally well tolerated. The most commonly reported adverse effects were dizziness, paresthesia, dry mouth, and fatigue. Pharmacologic studies demonstrated that frovatriptan is cerebroselective. Its selectivity for cerebral vessels lessens the potential for undesirable peripheral effects. Frovatriptan has a terminal deposition half-life of approximately 26 hours, which appears to be independent of age, gender, and renal function. This imparts that frovatriptan may be particularly well suited to patients with prolonged migraines and those who suffer migraine recurrence. Frovatriptan does not alter cytochrome P450 (CYP450) isoenzymes, as such it is unlikely to affect the metabolism of other drugs. No dosage adjustments are necessary based on age, renal, or mild to moderate hepatic impairment. Apart from its efficacy in the acute management of migraine, frovatriptan is an effective agent when used as either acute therapy or as intermittent prophylaxis therapy of menstrual migraines, particularly in women who do not respond to conventional therapies.

Safety and tolerability of frovatriptan in the acute treatment of migraine and prevention of menstrual migraine: Results of a new analysis of data from five previously published studies

BACKGROUND

Triptans are a recommended first-line treatment for moderate to severe migraine.

OBJECTIVE

Using clinical trial data, we evaluated the safety and tolerability of frovatriptan as acute treatment (AT) and as short-term preventive (STP) therapy for menstrual migraine (MM).

METHODS

Data from 2 Phase III AT trials (AT1: randomized, placebo controlled, 1 attack; AT2: 12-months, noncomparative, open label) and 3 Phase IIIb STP trials in MM (MMP1 and MMP2: randomized, placebo controlled, double blind, 3 perimenstrual periods; MMP3: open label, noncomparative, 12 perimenstrual periods) were analyzed. In AT1, patients treated each attack with frovatriptan 2.5 mg, sumatriptan 100 mg, or placebo. In AT2, they used frovatriptan 2.5 mg. In MMP1 and MMP2, women administered frovatriptan 2.5 mg for 6 days during the perimenstrual period, taking a loading dose of 2 or 4 tablets on day 1, followed by once-daily or BID frovatriptan 2.5 mg, respectively; in MMP3, they used BID frovatriptan 2.5 mg. In AT1, which was previously published in part, group differences in adverse events (AEs) were analyzed using the Fisher exact test, and response rates were compared using logistic regression. Post hoc analyses of sustained pain-free status with no AEs (SNAE) and sustained pain response with no AEs (SPRNAE) were performed using a 2-sample test for equality of proportions without continuity correction. For AT2 and the STP studies, data were summarized using descriptive statistics. Results of individual safety analyses for the STP studies were previously reported; the present report includes new results from a pooled analysis of MMP1 and MMP2 and a new analysis of MMP3 in which AEs were coded using Medical Dictionary for Regulatory Activities version 8.0.

RESULTS

AT1 included 1206 patients in the safety group; AT2 included 496. In the STP studies, safety data were collected for 1487 women. In AT1 and AT2, 85.6% and 88.3%, respectively, of enrolled patients were women. Overall, AEs were generally mild to moderate (AT studies: 82.3%-90.0%; STP studies: 78.9%89.5%). In AT1, 27.3% (131/480) of frovatriptan patients, 33.4% (161/482) of sumatriptan patients, and 14.8% (36/244) of placebo patients experienced an AE considered possibly or probably related to treatment (P < 0.001 for either drug vs placebo).There were no significant differences between frovatriptan and sumatriptan in SNAE at 4 to 24 hours or in SPRNAE at 2 to 24 hours or at 4 to 24 hours. In randomized, controlled STP trials for MM, AEs were reported by 57.8% (166/287, BID) and 63.4% (210/331, once daily) of frovatriptan users versus 62.8% (216/344) of placebo recipients. There were no consistent differences in AEs reported by patients with potential cardiovascular risk or in AEs related to the use of estrogencontaining contraceptives (ECCs).

CONCLUSIONS

In randomized controlled trials and 12-month open-label studies, frovatriptan was well tolerated in these women during AT and STP therapy for MM. Subgroup analyses provide preliminary evidence of tolerability in women using ECCs and in women with comorbidities that do not contraindicate triptan use but may be suggestive of cardiovascular risk.

Rapid responders to frovatriptan in acute migraine treatment: results from a long-term, open-label study

BACKGROUND

The chronic nature of migraine and the reliance on acute treatment constitute the basis of the present long-term, open-label study.

OBJECTIVES

First, assessment of the tolerability and safety of frovatriptan, 2.5-7.5 mg taken orally over 24 hours, for the acute treatment of migraine, repeatedly over a 12-month period. Second, assessment of the efficacy and tolerability of a second, double-blind dose of 2.5-mg frovatriptan, compared with placebo, for nonresponse at 2 hours after treatment of moderate or severe headache with 2.5-mg frovatriptan.

RESULTS

With regard to the first attack treated, 173 (36%) of the 486 subjects in the study did not take a second dose at 2 hours for nonresponse. At 2 hours and 4 hours, these "rapid responders" experienced a decrease in headache intensity from moderate or severe to mild or no pain in 84% and 98%, respectively ("headache response"). Six percent of them experienced recurrence of moderate or severe headache within 24 hours following a response at 4 hours and 12% took rescue medication. The response, measured in terms of median time to "complete migraine relief," was maintained over 30 subsequent migraine attacks, treated from attack 2 onwards over the course of 12 months.

CONCLUSION

Frovatriptan provides a remarkably fast and high headache response in a subgroup of more than one-third of migraineurs, with a very low 24-hour headache recurrence and low rescue medication intake.

5-Hydroxytryptamine receptors in the human cardiovascular system

The human cardiovascular system is exposed to plasma 5-hydroxytryptamine (5-HT, serotonin), usually released from platelets. 5-HT can produce harmful acute and chronic effects. The acute cardiac effects of 5-HT consist of tachycardia (preceded on occasion by a brief reflex bradycardia), increased atrial contractility and production of atrial arrhythmias. Acute inotropic, lusitropic and arrhythmic effects of 5-HT on human ventricle become conspicuous after inhibition of phosphodiesterase (PDE) activity. Human cardiostimulation is mediated through 5-HT4 receptors. Atrial and ventricular PDE3 activity exerts a protective role against potentially harmful cardiostimulation. Chronic exposure to high levels of 5-HT (from metastatic carcinoid tumours), the anorectic drug fenfluramine and its metabolites, as well as the ecstasy drug 3,4-methylenedioxymethamphetamine (MDMA) and its metabolite 3,4-methylenedioxyamphetamine (MDA) are associated with proliferative disease and thickening of cardiac valves, mediated through 5-HT2B receptors. 5-HT2B receptors have an obligatory physiological role in murine cardiac embryology but whether this happens in humans requires research. Congenital heart block (CHB) is, on occasion, associated with autoantibodies against 5-HT4 receptors. Acute vascular constriction by 5-HT is usually shared by 5-HT1B and 5-HT2A receptors, except in intracranial arteries which constrict only through 5-HT1B receptors. Both 5-HT1B and 5-HT2A receptors can mediate coronary artery spasm but only 5-HT1B receptors appear involved in coronary spasm of patients treated with triptans or with Prinzmetal angina. 5-HT2A receptors constrict the portal venous system including oesophageal collaterals in cirrhosis. Chronic exposure to 5-HT can contribute to pulmonary hypertension through activation of constrictor 5-HT1B receptors and proliferative 5-HT2B receptors, and possibly through direct intracellular effects.

Frovatriptan: clinical review and future directions

Triptan medications are selective serotonin receptor (5-HT1B/D) agonists approved for the treatment of acute migraine attacks. Among the currently available triptans, frovatriptan is unique with a long half-life (~26 h), metabolism by multiple pathways and a low side-effect profile. Clinical trial data demonstrates efficacy for frovatriptan across multiple doses, with the 2.5 mg dose selected for lower side effects. Frovatriptan is approved for use in the conventional treatment of an ongoing migraine attack, as are the other currently available triptan medications. The long half-life of frovatriptan has led to the initiation of studies of frovatriptan for the short-term prevention of menstrually related migraine attacks, during which patients are often difficult to treat. This newly investigated treatment approach for patients with predictable menstrually related migraine may, in the future, lead to treatment paradigms that benefit those patients with migraine attacks that are difficult to manage.

Triptans induce vasoconstriction of human arteries and veins from the thoracic wall

A common side effect of migraine treatment with triptans is chest symptoms. The origin of these symptoms is not known. The aim of the present study was to examine the vasocontractile effect of triptans in human arteries and veins from the thoracic wall and in coronary artery bypass grafts. In vitro pharmacology experiments showed that the 5-hydroxytryptamine (5-HT) type 1B and 1D receptor agonists, eletriptan, naratriptan, rizatriptan, sumatriptan, and zolmitriptan, induced vasoconstriction in the thoracic blood vessels from 38% to 57% of the patients. 5-carboxamidotryptamine (5-CT) and sumatriptan elicited a vasoconstriction that was antagonized by the 5-HT1B receptor antagonist SB224289, whereas the 5-HT1D receptor antagonist BRL115572 had no effect. 5-HT induced a contraction that was inhibited by the 5-HT2A receptor antagonist ketanserin. 5-HT2A, 5-HT1B, and 5-HT1D receptor mRNA levels were detected by real-time PCR in all blood vessels studied. In conclusion, triptans induce vasoconstriction in arteries and veins from the thoracic wall, most likely by activation of 5-HT1B receptors. This response could be observed in only 38% to 57% of the patients, which may provide an explanation for why a similar number of patients experience chest symptoms as a side effect of migraine treatment with triptans.

Evidence for 5-HT2B and 5-HT7 receptor-mediated relaxation in pulmonary arteries of weaned pigs

This study characterizes the relaxant response to 5-hydroxytryptamine (5-HT) in prostaglandin F(2alpha) (PGF(2alpha))-precontracted pulmonary arteries of weaned pigs. In arterial rings with intact endothelium, the relaxation to 5-HT was biphasic. The high affinity component of relaxation to 5-HT (0.1-10 nM) was abolished by mechanical removal of the endothelium or after the addition of L: -NAME (200 microM), and was inhibited by the 5-HT(2B/2C) receptor antagonist SB 206553 (1 microM), but not the 5-HT(2C) receptor antagonist SB 242084 (0.1 microM). Endothelium-intact arteries were also relaxed by the selective 5-HT(2B) receptor agonist BW 723C86 (pD(2) 7.7). The relaxant response to BW 723C86 was inhibited by 1 microM SB 206553 (pK(B) 6.8). The low affinity component of relaxation to 5-HT (>/=30 nM) remained unaffected after mechanical removal of the endothelium or the addition of L: -NAME. In endothelium-denuded arterial rings, 5-HT, 5-carboxamidotryptamine (5-CT), 5-methoxytryptamine (5-MeOT), and frovatriptan produced monophasic relaxations with pD(2) values of 6.5, 7.5, 5.9, and 4.7 respectively. Relaxant responses to the agonists were antagonized by the selective 5-HT(7) receptor antagonist SB 269970 (pK(B) 8.2-8.9). The relaxant response to the potent 5-HT(7) receptor agonist 5-CT was also antagonized by methiothepin (pK(B) 9.6), pimozide (pK(B) 8.2), mesulergine (pK(B) 7.7), methysergide (pK(B) 7.4), clozapine (pK(B) 7.6), and spiperone (pK(B) 7.4). The estimated pK(B) values argue in favor of an involvement of 5-HT(7) receptors in the direct vasorelaxant action of 5-HT in the pulmonary arteries of weaned pigs. The relaxant response to 5-CT was associated with an increase in cAMP that was surmountably antagonized by SB 269970 (pK(B) 8.6). The present in vitro bioassay can be used to characterize new drugs with potential agonist or antagonist properties at functional 5-HT(7) receptors.

Frovatriptan use in migraineurs with or at high risk of coronary artery disease

OBJECTIVE

To investigate the cardiovascular effects of frovatriptan 2.5 mg during a migraine attack in patients with, or at high risk of, coronary artery disease.

BACKGROUND

Rare occurrences of myocardial ischemia and coronary and peripheral vasospasm associated with the use of sumatriptan have triggered concern over the vasoconstrictor properties of the triptan class of drugs.

METHODS

This randomized, double-blind, placebo-controlled, parallel-group study was conducted in 14 US private headache referral centers or clinics. Seventy-five patients, aged 18 years and older, with a history of migraine who were at high risk (Framingham score > or =14) of or who had previously documented coronary artery disease were evaluated.

RESULTS

Incidence of clinically significant electrocardiogram changes was higher at all time points postdose with placebo than with frovatriptan, reaching statistical significance at 4 hours (40% versus 19%, P=.026). Similar proportions of patients had ischemia documented on Holter monitoring in the placebo (13%) and frovatriptan (11%) groups, and the incidence of arrhythmias was higher in the placebo group (11% versus 3%). There were no clinically significant changes in heart rate or blood pressure in either group. Adverse event profiles were similar for placebo and frovatriptan.

CONCLUSIONS

In this exploratory study of migraineurs with, or at high risk of, coronary artery disease, frovatriptan 2.5 mg was well tolerated and not associated with an increase in cardiovascular monitoring abnormalities.

Coronary vasoconstrictor potential of triptans: a review of in vitro pharmacologic data

This article reviews the in vitro pharmacology of the triptans in human isolated coronary arteries. As expected, based on their similar pharmacologic profiles, the triptans cannot be easily differentiated with respect to effects at human isolated coronary arteries. Furthermore, the data show that at therapeutically relevant concentrations, triptans have little potential to cause clinically significant constriction of nondiseased coronary arteries. These data, considered in the context of clinical findings reviewed elsewhere in this supplement, support the conclusion that, while all triptans have the potential to produce small contractions of human isolated coronary arteries, their craniovascular selectivity, when used at therapeutic doses, renders them unlikely to cause serious adverse coronary events in patients with healthy coronary arteries.

Frovatriptan succinate, a 5-HT1B/1D receptor agonist for migraine

Frovatriptan succinate is one of the most recent serotonin receptor agonists to receive FDA, approved labelling for use in the acute management of migraine with or without aura in adults. The mechanism of action of frovatriptan is thought to be similar to that of a serotonin agonist. However, frovatriptan has distinctive pharmacokinetic and pharmacologic properties, chiefly, a high affinity for serotonin receptors 1B and 1D and a long elimination half-life; frovatriptan was shown to be more selective for cerebral than coronary arteries, a property which makes frovatriptan more favourable in patients at risk of coronary artery disease. Additionally, frovatriptan has a half-life of approximately 25 h, substantially longer than that of any other agent within its class. This property makes frovatriptan suitable for patients who typically suffer migraines of long duration and/or those who suffer migraine recurrence. The efficacy of frovatriptan in the treatment of acute migraine was demonstrated in five double-blind, randomised, placebo-controlled trials. At 2h, headache response rates for frovatriptan 2.5 mg ranged from 38 to 40% compared to 22-35% for placebo. Headache recurrence for frovatriptan 2.5 mg at 24h ranged from 9 to 14% compared with 18% in placebo subjects. Frovatriptan has no clinically significant pharmacokinetic interactions with drugs used for migraine prophylaxis or with commonly prescribed medications. Adverse effects of frovatriptan including dizziness, paresthesia, dry mouth, fatigue and flushing were generally mild and well tolerated. Given the fact that patient response to serotonin agonists is individualised, and selecting an effective agent may involve trial and error, frovatriptan is a welcome alternative in the acute management of migraine.

Consensus Statement: Cardiovascular Safety Profile of Triptans (5-HT1B/1D Agonists) in the Acute Treatment of Migraine

BACKGROUND

Health care providers frequently cite concerns about cardiovascular safety of the triptans as a barrier to their use. In 2002, the American Headache Society convened the Triptan Cardiovascular Safety Expert Panel to evaluate the evidence on triptan-associated cardiovascular risk and to formulate consensus recommendations for making informed decisions for their use in patients with migraine.

OBJECTIVE

To summarize the evidence reviewed by the Triptan Cardiovascular Safety Expert Panel and their recommendations for the use of triptans in clinical practice.

PARTICIPANTS

The Triptan Cardiovascular Safety Expert Panel was composed of a multidisciplinary group of experts in neurology, primary care, cardiology, pharmacology, women's health, and epidemiology.

EVIDENCE AND CONSENSUS PROCESS

An exhaustive search of the relevant published literature was reviewed by each panel member in preparation for an open roundtable meeting. Pertinent issues (eg, cardiovascular pharmacology of triptans, epidemiology of cardiovascular disease, cardiovascular risk assessment, migraine) were presented as a prelude to group discussion and formulation of consensus conclusions and recommendations. Follow-up meetings were held by telephone.

CONCLUSIONS

(1) Most of the data on triptans are derived from patients without known coronary artery disease. (2) Chest symptoms occurring during use of triptans are generally nonserious and are not explained by ischemia. (3) The incidence of serious cardiovascular events with triptans in both clinical trials and clinical practice appears to be extremely low. (4) The cardiovascular risk-benefit profile of triptans favors their use in the absence of contraindications.

5-Hydroxytryptamine1B receptor-mediated contraction of rabbit saphenous vein and basilar artery: role of vascular endothelium

This study characterizes the sumatriptan-sensitive [5-hydroxytryptamine (5-HT)(1B/1D)] receptor in rabbit saphenous vein and basilar artery. (S)-(-)-1-[2-[4-(4-Methoxy-phenyl)-piperazin-1-yl]-ethyl]isochroman-6-carboxylic acid methylamide (PNU-109291), a 5-HT(1D) subtype-selective agonist (human K(i) = 2.5 +/- 0.07 nM), did not contract either tissue, whereas o-methoxyphenylpiperazide derivative 4F (MPPA-4F), a 5-HT(1B) subtype-selective antagonist (human K(i) = 4.6 +/- 0.6 nM) potently inhibited sumatriptan-induced contraction in the saphenous vein and basilar artery. These results suggested that sumatriptan-induced contraction was mediated via the 5-HT(1B) receptor in these blood vessels. 5-HT(1B) receptor-mediated contraction was then compared in endothelium-intact and denuded vessels to evaluate the role of the endothelium in regulating sumatriptan-induced contractility in these tissues. The presence of an intact endothelium inhibited 5-HT(1B)-induced contraction in both tissues. Endothelial denudation or nitric-oxide synthase inhibition with N(omega) nitro-L-arginine methyl ester (L-NAME) (100 microM) increased the efficacy and potency of sumatriptan in the saphenous vein and basilar artery. Surprisingly, in endothelial-denuded vascular tissues, L-NAME (100 microM) also significantly increased the maximal 5-HT(1B) receptor-induced contraction in both tissues, with no effect on potency of sumatriptan. The effect of L-NAME after endothelial denudation may reflect the presence of a low density of residual endothelial cells as estimated by CD31 antibody staining combined with the modulating effect of nitric oxide released from nonendothelial cells in vascular tissue. Endothelial modulation was specific to 5-HT(1B) receptors because removal of the endothelium did not significantly alter contraction to norepinephrine, histamine, prostaglandin, or potassium chloride in the saphenous vein or basilar artery.

Comparison of contractile responses to donitriptan and sumatriptan in the human middle meningeal and coronary arteries

Donitriptan is a potent, high efficacy agonist at 5-HT(1B/1D) receptors. We investigated the contractile effects of donitriptan and sumatriptan on human isolated blood vessels of relevance to therapeutic efficacy in migraine (middle meningeal artery) and coronary adverse events (coronary artery). Furthermore, using the concentration-response curves in the middle meningeal artery, we predicted the plasma concentration needed for the therapeutic effect of donitriptan. Both donitriptan and sumatriptan contracted the middle meningeal artery with similar apparent efficacy (E(max): 103+/-8% and 110+/-12%, respectively), but the potency of donitriptan (pEC(50): 9.07+/-0.14) was significantly higher than that of sumatriptan (pEC(50): 7.41+/-0.08). In the coronary artery, the contraction to donitriptan was biphasic with a significantly higher maximal response (E(max): 29+/-6%) than sumatriptan (E(max): 14+/-2%; pEC(50): 5.71+/-0.16), yielding two distinct pEC(50) values (8.25+/-0.16 and 5.60+/-0.24). Incubation with the 5-HT(2) receptor antagonist ketanserin (10 microM) eliminated the low affinity component of the concentration-response curve of donitriptan and the resultant E(max) and pEC(50) were 9+/-2% and 7.33+/-0.21, respectively. Ketanserin was without effect on the sumatriptan-induced contraction. Based on the middle meningeal artery contraction, concentrations (C(max)) of donitriptan that may be expected to have a therapeutic efficacy equivalent to that of 50 and 100 mg sumatriptan are predicted to be around 2.5 and 4.3 nM, respectively. Such concentrations are likely to induce only a small coronary artery contraction of 2.9+/-1.5% and 3.8+/-2.0%, respectively; these are not different from those by C(max) concentrations of sumatriptan (1.7+/-0.4% or 2.2+/-0.4%). The present results suggest that, like sumatriptan, donitriptan exhibits cranioselectivity and would be effective in aborting migraine attacks with a similar coronary side-effect profile as sumatriptan.

Frovatriptan: a review of drug-drug interactions

OBJECTIVE

To investigate the potential for interactions involving drugs likely to be coadministered with frovatriptan.

BACKGROUND

Frovatriptan is a new 5-hydroxytryptamine (5-HT)(1B/1D) agonist. Preclinical data suggest that the pharmacokinetic and pharmacological profile of frovatriptan may differ from that of the currently available triptans.

METHODS

The potential for interactions between frovatriptan and other drugs was investigated using in vitro methods, studies in healthy volunteers, and retrospective analysis of data from phase I trials.

RESULTS

In vitro, frovatriptan was principally metabolized by cytochrome P-450 (CYP) 1A2 but was found not to be an inhibitor or inducer of this or other CYP isoenzymes. Frovatriptan was only a weak inhibitor of monoamine oxidase at very high concentrations in vitro and was not a substrate for this enzyme (unlike some other triptans). Coadministration with moclobemide, at doses known to inhibit monoamine oxidase-A, did not affect the pharmacokinetics of frovatriptan. Binding to plasma proteins was low (15%), and binding to erythrocytes was moderate (60%) and unlikely to be a source of interaction with other drugs. The pharmacokinetics of frovatriptan were not affected by moderate alcohol intake. There were slight increases in area under the curve and maximum concentration on concomitant administration with the combined oral contraceptives, propranolol, and fluvoxamine; and slight decreases in these parameters on concomitant administration with ergotamine and in tobacco smokers; these findings were considered to have no clinical significance in view of frovatriptan's large therapeutic index (well tolerated at doses ranging from 2.5 to 40 mg). These effects can be attributed primarily to modification of CYP1A2 activity but their impact is limited, probably due to frovatriptan also undergoing renal clearance and the likely role of blood cell binding in controlling the amount of unbound drug available for elimination.

CONCLUSIONS

Because it has no inhibitory or inducing effect on CYP isoenzymes and is only slightly bound to plasma proteins, it is unlikely that frovatriptan will alter the pharmacokinetics of concomitantly administered drugs. Frovatriptan, therefore, appears to have a low risk of interaction with other drugs, and adjustments of dose are unlikely to be required when it is coadministered with other agents.

Clinical pharmacokinetics of frovatriptan

OBJECTIVE

To review available data on the clinical pharmacokinetics of frovatriptan.

BACKGROUND

Preclinical data suggest that the pharmacokinetic profile of frovatriptan may differ from that of the currently available triptans.

METHODS

Studies of healthy volunteers, subjects with renal or hepatic impairment, elderly subjects, and patients with migraine during and between attacks were reviewed.

RESULTS

Oral bioavailability of frovatriptan is 22% to 30%, and although the time to maximum concentration is typically 2 to 3 hours, approximately 60% to 70% of plasma maximum concentration is achieved within 1 hour of dosing. Frovatriptan distributes into erythrocytes, with binding reversible and time dependent. The relatively long terminal elimination half-life (about 26 hours) confers good systemic exposure and may produce a long duration of therapeutic action, thus reducing migraine recurrence and the need for redosing. Systemic exposure to frovatriptan generally correlates with dose between 1 and 100 mg. Blood and plasma frovatriptan concentrations are consistently higher in females, but there is no need to adjust dose according to gender. Pharmacokinetics are essentially unaffected by food and were predictable after repeat dosing; steady state is approached in about 4 to 5 days. Pharmacokinetics were changed only slightly in subjects with renal impairment or mild-to-moderate hepatic impairment, elderly individuals, and during migraine attacks. Frovatriptan is principally metabolized by the CYP1A2 isoenzyme of cytochrome P-450 and is cleared by the kidney and liver, each having sufficient capacity to compensate for impairment of the other.

CONCLUSIONS

Frovatriptan can be taken without regard for food intake, and because of the large therapeutic margin and shallow dose-response curve, there is no need for dosage adjustment in the elderly, in women taking a combined oral contraceptive, in patients with mild-to-severe renal impairment, mild-to-moderate hepatic impairment, or according to gender. The long duration of exposure may reduce the likelihood of early migraine recurrence.

Pharmacology of the selective 5-HT(1B/1D) agonist frovatriptan

OBJECTIVE

To determine the pharmacological profile of frovatriptan.

BACKGROUND

Frovatriptan is a new 5-HT(1B/1D) agonist developed for the treatment of migraine.

METHODS

Pharmacological studies were performed using in vitro and in vivo techniques.

RESULTS

Radioligand-binding studies showed that frovatriptan has a high affinity for 5-HT(1B) and 5-HT(1D) receptors, and moderate affinity for 5-HT(1A), 5-HT(1F), and 5-HT(7) receptors. In vitro, frovatriptan acts as a potent full agonist at human cloned 5-HT(1B) and 5-HT(1D) receptors, and as a moderately potent full agonist at 5-HT(7) receptors. Studies of frovatriptan in isolated human arteries demonstrated a lower threshold for constriction of cerebral than coronary vasculature and a bell-shaped dose-response curve was apparent in the coronary arteries. In anesthetized dogs, frovatriptan administration produced no measurable effect on cardiac function or on blood pressure. Frovatriptan had no effects on coronary blood flow following transient coronary artery occlusion, whereas sumatriptan produced a prolonged and significant decrease in coronary blood flow.

CONCLUSION

The pharmacology of frovatriptan suggests that it should be an effective agent for the acute treatment of migraine, with a low potential for undesirable peripheral effects.

Frovatriptan Succinate

Each month, subscribers to The Formulary® Monograph Service receive five to six well-documented monographs on drugs that are newly released or are in late Phase III trials. The monographs are targeted to your Pharmacy and Therapeutics Committee. Subscribers also receive monthly one-page summary monographs on the agents that are useful for agendas and pharmacy/nursing in-ser-vices. A comprehensive target drug utilization evaluation (DUE) is also provided each month. The monographs are published in printed form and on diskettes that allow customization. Subscribers to the The Formulary Monograph Service also receive access to a pharmacy bulletin board, The Formulary Information Exchange (The F.I.X). All topics pertinent to clinical and hospital pharmacy are discussed on The F.I.X.

Through the cooperation of The Formulary, Hospital Pharmacy publishes selected reviews in this column. If you would like information about The Formulary Monograph Service or The F.I.X., call The Formulary at 800-322-4349. The April 2002 Formulary monograph topics are pegfilgrastim, fondaparinux sodium, dutasteride, aripiprazole, and ezetimibe. The DUE is on drotrecogin alfa.

Dose range-finding studies with frovatriptan in the acute treatment of migraine

OBJECTIVE

To determine the optimum dose of frovatriptan for the acute treatment of migraine.

BACKGROUND

Frovatriptan is a new triptan developed for the acute treatment of migraine. The dose-response characteristics and safety of frovatriptan have been investigated across a broad range of doses from 0.5 to 40 mg.

DESIGN

Two randomized, placebo-controlled, double-blind, parallel-group trials, with a total of 1453 patients, were performed to determine the optimal dose of the 5-HT(B/1D)agonist, frovatriptan, for the acute treatment of migraine. The dose ranges studied were 2.5 to 40 mg in the high-dose study and 0.5 to 5 mg in the low-dose study.

RESULTS

At 2 hours postdosing for initial moderate or severe headache (International Headache Society grades 2 or 3), there was an approximate two-fold difference in the proportion of patients taking frovatriptan doses of 2.5 to 40 mg with mild or no headache compared to placebo. Frovatriptan doses of 0.5 mg and 1 mg were not more effective than placebo at 2 hours postdose, and 2.5 mg was identified as the lowest effective dose for the relief of migraine and accompanying symptoms. Above 2.5 mg, no dose-response relationship was observed for any efficacy parameters. There was an increase in the incidence of adverse events from 10 mg and above, but the vast majority were rated as mild in severity and did not impact upon tolerability in a significant manner.

CONCLUSIONS

Frovatriptan was well tolerated throughout the dose range of 0.5 to 40 mg. The 2.5-mg dose confers the optimal balance of efficacy and tolerability for the acute treatment of migraine.

Tolerability and safety of frovatriptan with short- and long-term use for treatment of migraine and in comparison with sumatriptan

OBJECTIVE

To evaluate the tolerability and safety of frovatriptan 2.5 mg in patients with migraine.

BACKGROUND

Frovatriptan is a new, selective serotonin agonist (triptan) developed for the acute treatment of migraine. Dose range-finding studies identified 2.5 mg as the dose that conferred the optimal combination of efficacy and tolerability.

METHODS

The tolerability and safety of frovatriptan 2.5 mg were assessed during controlled, acute migraine treatment studies, including a study that compared frovatriptan 2.5 mg with sumatriptan 100 mg, as well as a 12-month open-label study during which patients could take up to three doses of frovatriptan 2.5 mg within a 24-hour period. Safety and tolerability were assessed through the collection of adverse events, monitoring of heart rate and blood pressure performance of 12-lead electrocardiogram, hematology screen, and blood chemistry studies.

RESULTS

In the short-term studies, 1554 patients took frovatriptan 2.5 mg and 838 took placebo. In the 12-month study, 496 patients treated 13 878 migraine attacks. Frovatriptan was well tolerated in the short- and long-term studies with 1% of patients in the short-term studies and 5% of patients in the long-term study withdrawing due to lack of tolerability. The incidence of adverse events was higher in the frovatriptan-treated patients than in the patients who took placebo (47% versus 34%) and the spectrum of adverse events was similar. When compared to sumatriptan 100 mg, significantly fewer patients taking frovatriptan experienced adverse events (43% versus 36%; P=.03) and the number of adverse events was lower (0.62 versus 0.91), there were also fewer adverse events suggestive of cardiovascular symptoms in the frovatriptan group. Analysis of the entire clinical database (n=2392) demonstrated that frovatriptan was well tolerated by the patients regardless of their age, gender, race, concomitant medication, or the presence of cardiovascular risk factors. No effects of frovatriptan on heart rate, blood pressure, 12-lead electrocardiogram, hematology screen, or blood chemistry were observed. No patient suffered any treatment-related serious adverse event.

CONCLUSIONS

Short- and long-term use of frovatriptan 2.5 mg was well tolerated by a wide variety of patients. Frovatriptan treatment produced an adverse events profile similar to that of placebo, and in a direct comparison study was better tolerated than sumatriptan 100 mg.

Characterization of sumatriptan-induced contractions in human isolated blood vessels using selective 5-HT(1B) and 5-HT(1D) receptor antagonists and in situ hybridization

The 5-HT(1B/1D) receptor agonist sumatriptan is effective in aborting acute attacks of migraine and is known to cause constriction of cranial arteries as well as some peripheral blood vessels. The present study set out to investigate whether 5-HT(1B) and/or 5-HT(1D) receptors mediate contractions of the human isolated middle meningeal and temporal arteries (models for anti-migraine efficacy) and coronary artery and saphenous vein (models for side-effect potential). Concentration-response curves were made with sumatriptan (1 nm-100 microm) in blood vessels in the absence or presence of selective antagonists at 5-HT(1B) (SB224289) and 5-HT(1D) (BRL15572) receptors. SB224289 antagonized sumatriptan-induced contractions in all blood vessels, although the antagonism profile was different amongst these blood vessels. In the temporal artery, SB224289 abolished contraction to sumatriptan, whereas in the middle meningeal artery and saphenous vein sumatriptan-induced contractions were blocked in an insurmountable fashion. Moreover, SB224289 acted as a weak surmountable antagonist in the coronary artery (pK(B): 6.4 +/- 0.2). In contrast, BRL15572 had little or no effect on sumatriptan-induced contractions in the four blood vessels investigated. In situ hybridization revealed the expression of 5-HT(1B) receptor mRNA in the smooth muscle as well as endothelial cells of the blood vessels, whereas the mRNA for the 5-HT(1D) receptor was only very weakly expressed. These results show that the 5-HT(1B) receptor is primarily involved in sumatriptan-induced contractions of human cranial as well as peripheral blood vessels.

Calcium-antagonistic activity of sumatriptan in the rat anococcygeus muscle

The relaxant effect of sumatriptan, a 5-HT(1B/1D) receptor agonist, on the rat anococcygeus muscle was investigated. Sumatriptan induced concentration-dependent relaxations of the phenylephrine-precontracted rat anococcygeus muscle. N(G)-nitro-L-arginine, methylene blue, glibenclamide, tetrodotoxin, indomethacin, GR 113808, GR 55562, methysergide, ketanserin, ICS 205930, clozapine, methiothepin, metergoline, mesulergine, and ritanserin did not inhibit the relaxations induced by sumatriptan. Sumatriptan converted calcium-induced contractions into relaxations in the preparations depolarized by a calcium-free, high-potassium solution. In membrane preparations obtained from the rat anococcygeus muscle, the basal rate of cAMP production by adenylate cyclase was 4.77 +/- 0.02 pmol/mg protein/min (n = 15). The enzyme activity was increased to 104 +/- 51.7 pmol/mg protein/min by forskolin (10(-4) mol/l), but did not change in the presence of sumatriptan. The mRNA expression of 5-HT(1B), 5-HT(1D), and 5-HT(7) receptors was not observed in the rat anococcygeus muscle. The results indicate that sumatriptan causes relaxation of the precontracted rat anococcygeus muscle by a calcium-antagonistic activity.

Frovatriptan for the acute treatment of migraine: a dose-finding study

OBJECTIVE

To determine the optimal dose and tolerability of frovatriptan in the acute treatment of migraine.

BACKGROUND

Frovatriptan has a distinctive pharmacological and pharmacokinetic profile compared with sumatriptan. A previous study has shown that frovatriptan doses of 2.5, 5, 10, 20, and 40 mg are equally effective in relieving headache with no evidence of a dose-response relationship. The incidence of adverse events tended to increase with doses of 10 mg and above.

METHODS

This study was a randomized, double-blind, placebo-controlled, parallel-group multicenter trial. Patients (n=635) took a single oral dose of placebo or frovatriptan, 0.5, 1, 2.5, or 5 mg, at the onset of a moderate or severe migraine headache and recorded headache intensity, functional impairment, and migraine-associated symptoms over 24 hours.

RESULTS

Frovatriptan 2.5 mg produced clinically and statistically significant headache relief 2 hours post-dose, whereas the effect of lower doses was not significantly different from that of placebo at that time point. The 2.5-mg dose also produced significant symptom relief and improvement in functional impairment. All doses of frovatriptan were well tolerated, and the majority of adverse events were of mild or moderate severity.

CONCLUSION

It is concluded that the 2.5-mg dose of frovatriptan offers optimal efficacy and tolerability in the treatment of acute migraine. Higher doses do not appear to confer greater efficacy and are associated with an increased incidence of adverse effects.

Vascular effects of the new anti-migraine agent almotriptan on human cranial and peripheral arteries

This paper describes the vascular effects of almotriptan in comparison with sumatriptan in human vessels and tissues in vitro. The contractile properties of almotriptan and sumatriptan were evaluated in vitro in the following arteries: meningeal, temporal, basilar, internal carotid, ophthalmic, pulmonary and coronary. In addition, the effects of almotriptan on the pulmonary vein and on bronchial tissues were studied. Almotriptan showed selectivity of action for migraine-related arteries (i.e. contractile EC(50) of 30 and 700 nm for meningeal and temporal arteries, respectively), whereas the effect on arteries supplying blood to the brain was lower. The contractile effect of almotriptan was lower than that of sumatriptan in pulmonary arteries, whereas in bronchial preparations no clinically relevant contractile responses were observed for either almotriptan or sumatriptan. In ophthalmic arteries the contractile effects of almotriptan and sumatriptan were similar, whereas lower contractile effects were obtained with almotriptan than with sumatriptan in coronary arteries.

Pharmacokinetics and pharmacodynamics of the triptan antimigraine agents: a comparative review

The current approach to antimigraine therapy comprises potent serotonin 5-HT1B/1D receptor agonists collectively termed triptans. Sumatriptan was the first of these compounds to be developed, and offered improved efficacy and tolerability over ergot-derived compounds. The development of sumatriptan was quickly followed by a number of 'second generation' triptan compounds, characterised by improved pharmacokinetic properties and/or tolerability profiles. Triptans are believed to effect migraine relief by binding to serotonin (5-hydroxy-tryptamine) receptors in the brain, where they act to induce vasoconstriction of extracerebral blood vessels and also reduce neurogenic inflammation. Although the pharmacological mechanism of the triptans is similar, their pharmacokinetic properties are distinct. For example, bioavailability of oral formulations ranges between 14% (sumatriptan) and 74% (naratriptan), and their elimination half-life ranges from 2 hours (sumatriptan and rizatriptan) to 25 hours (frovatriptan). Clearly, such diverse pharmacokinetic properties will influence the effectiveness of the compounds and favour the prescription of one over another in different patient populations. This article reviews the pharmacological properties of the triptans (time to peak plasma concentration, half-life, bioavailability and receptor binding) and relates these properties to efficacy and time of onset. It also considers the effects of concomitant medication, food, age and disease on the pharmacokinetics of the compounds. In addition, the relative merits, such as headache recurrence, tolerability and route of administration, are discussed. Finally, the performance of the triptans is considered in the context of direct head-to-head comparative trials that have assessed the efficacy profile of the compounds.

Comparative effects of frovatriptan and sumatriptan on coronary and internal carotid vascular haemodynamics in conscious dogs

The effects of frovatriptan and sumatriptan on internal carotid and coronary vascular haemodynamics were investigated and compared in conscious dogs. Frovatriptan and sumatriptan (0.1 - 100 microg kg(-1)) induced a transient increase in external coronary artery diameter (eCOD) of up to 2.9+/-1.2 and 1.8+/-0.6%, respectively (both P:<0.05). This was followed by a prolonged and dose-dependent decrease in eCOD of up to -5.2+/-1.2 and -5.3+/-0.9% (both P:<0.05), with ED(50) values of 86+/-21 and 489+/-113 micromol kg(-1), respectively. In contrast, only a decrease in the external diameter of the internal carotid artery was observed (-6.0+/-0.6 and -6.2+/-1.4%, both P:<0.05, and ED(50) values of 86+/-41 and 493+/-162 micromol kg(-1), respectively). Frovatriptan was thus 5.7 fold more potent than sumatriptan at the level of both large coronary and internal carotid arteries. After endothelium removal by balloon angioplasty in coronary arteries, the initial dilatation induced by the triptans was abolished and delayed constriction enhanced. The selective antagonist for the 5-HT(1B) receptors SB224289 dose-dependently blocked the effects of sumatriptan on large coronary and internal carotid arteries whereas the selective antagonist for the 5-HT(1D) receptors BRL15572 did not affect any of these effects. In conclusion, frovatriptan and sumatriptan initially dilate and subsequently constrict large coronary arteries in the conscious dog, whereas they directly constrict the internal carotid artery. The vascular endothelium modulates the effects of these triptans on large coronary arteries. Finally, 5-HT(1B) but not 5-HT(1D) receptors are primarily involved in canine coronary and internal carotid vasomotor responses to sumatriptan.

Triptans in migraine: a comparative review of pharmacology, pharmacokinetics and efficacy

Triptans are a new class of compounds developed for the treatment of migraine attacks. The first of the class, sumatriptan, and the newer triptans (zolmitriptan, naratriptan, rizatriptan, eletriptan, almotriptan and frovatriptan) display high agonist activity at mainly the serotonin 5-HT1B and 5-HT1D receptor subtypes. As expected for a class of compounds developed for affinity at a specific receptor, there are minor pharmacodynamic differences between the triptans. Sumatriptan has a low oral bioavailability (14%) and all the newer triptans have an improved oral bioavailability and for one, risatriptan, the rate of absorption is faster. The half-lives of naratriptan, eletriptan and, in particular, frovatriptan (26 to 30h) are longer than that of sumatriptan (2h). These pharmacokinetic improvements of the newer triptans so far seem to have only resulted in minor differences in their efficacy in migraine. Double-blind, randomised clinical trials (RCTs) comparing the different triptans and triptans with other medication should ideally be the basis for judging their place in migraine therapy. In only 15 of the 83 reported RCTs were 2 triptans compared, and in 11 trials triptans were compared with other drugs. Therefore, in all placebo-controlled randomised clinical trials, the relative efficacy of the triptans was also judged by calculating the therapeutic gain (i.e. percentage response for active minus percentage response for placebo). The mean therapeutic gain with subcutaneous sumatriptan 6mg (51%) was more than that for all other dosage forms of triptans (oral sumatriptan 100mg 32%; oral sumatriptan 50mg 29%: intranasal sumatriptan 20mg 30%; rectal sumatriptan 25mg 31%; oral zolmitriptan 2.5mg 32%; oral rizatriptan 10mg 37%; oral eletriptan 40mg 37%; oral almotriptan 12.5mg 26%). Compared with oral sumatriptan 100mg (32%), the mean therapeutic gain was higher with oral eletriptan 80mg (42%) but lower with oral naratriptan 2.5mg (22%) or oral frovatriptan 2.5mg (16%). The few direct comparative randomised clinical trials with oral triptans reveal the same picture. Recurrence of headache within 24 hours after an initial successful response occurs in 30 to 40% of sumatriptan-treated patients. Apart from naratriptan, which has a tendency towards less recurrence, there appears to be no consistent difference in recurrence rates between the newer triptans and sumatriptan. Rizatriptan with its shorter time to maximum concentration (tmax) tended to produce a quicker onset of headache relief than sumatriptan and zolmitriptan. The place of triptans compared with non-triptan drugs in migraine therapy remains to be established and further RCTs are required.

Pharmacological analysis of contractile effects of eletriptan and sumatriptan on human isolated blood vessels

Eletriptan, a second-generation triptan with high affinity for 5-HT(1B/1D) receptors, is highly effective in migraine, with or without aura. We compared the effects of eletriptan and sumatriptan on the human isolated middle meningeal and coronary arteries and saphenous vein, used as models for therapeutic efficacy and potential side effects, and have investigated the role of 5-HT(1B/1D) receptors in contractions induced by these triptans. Concentration-response curves to eletriptan and sumatriptan were constructed in the absence or presence of a selective 5-HT(1B/1D) receptor antagonist, N-[4-methoxy-3-(4-methylpiperazin-1-yl)phenyl]-3-methyl-4-(4-py rid yl) benzamide (GR125743). All three blood vessels constricted in response to eletriptan and sumatriptan, but the middle meningeal artery relaxed following the highest concentration (100 microM) of eletriptan. In the middle meningeal artery, GR125743 antagonised the contractions induced by both eletriptan (pEC(50): 7.34+/-0.13) and sumatriptan (pEC(50): 6.91+/-0.17) to a similar degree (pA(2): 8. 81+/-0.17 and 8.64+/-0.21, respectively). In the human coronary artery and saphenous vein, sumatriptan-induced contractions (pEC(50): 6.24+/-0.14 and 6.19+/-0.12, respectively) were also potently antagonised by GR125743 (pA(2): 8.18+/-0.27 and 8.34+/-0.12, respectively). The eletriptan-induced contractions of the human saphenous vein (pEC(50): 6.09+/-0.13) were antagonised less effectively by GR125743 (pK(B): 7.73+/-0.18), and those of the human coronary artery (pEC(50): 5.54+/-0.22) remained unaffected by GR125743 up to a concentration of 100 nM. These results suggest that (i) based on the differences in pEC(50) values, the cranioselectivity of eletriptan (63-fold) is higher than that of sumatriptan (5-fold) in coronary artery, (ii) the contractile effects of sumatriptan and eletriptan (lower concentrations) in the three blood vessels are mediated via the 5-HT(1B) receptor, and (iii) additional mechanisms seem to be involved in coronary artery and saphenous vein contractions and middle meningeal artery relaxation following high concentrations of eletriptan.

Current and emerging second-generation triptans in acute migraine therapy: a comparative review

Sterile neurogenic inflammation within cephalic tissue, involving vasodilation and plasma protein extravasation, has been proposed as a pathophysiological mechanism in acute migraine. The action of 5-hydroxytryptamine (5-HT1B/1D) agonists--so-called triptans--on receptors located in meningeal arteries (5-HT1B) and trigeminovascular fiber endings (5-HT1D) has an inhibitory effect on this neurogenic inflammation. Recently, a series of second-generation 5-HT1B/1D agonists (almotriptan, eletriptan, frovatriptan, naratriptan, rizatriptan, and zolmitriptan) have been developed and are reviewed in this article. Their in vitro pharmacological properties, pharmacokinetics, clinical efficacy, drug interactions, and adverse effects are evaluated and compared to the golden standard in the treatment of acute migraine, sumatriptan.

Migraine pharmacotherapy with oral triptans: a rational approach to clinical management

The recent clinical development of a number of migraine specific 5-HT1B/1D agonist triptans with enhanced lipophilicity (TELs), relative to the first drug of this class sumatriptan, and with a range of different metabolic, pharmacokinetic and receptor affinity profiles, provides the potential for critically different clinical profiles. Eletriptan, naratriptan, rizatriptan and zolmitriptan display both increased stability to first pass metabolic inactivation by monoamine oxidase (MAO-A) and enhanced lipophilicity (4- to > 120-fold more than sumatriptan), leading to increased oral bioavailability (2- to 5-fold more than the 14% reported for oral sumatriptan). Central penetration and increased receptor affinity and selectivity for the neuronal (5-HT1D) receptor also combine to allow for lower total oral dosing (i.e., unit doses of 15 mg or less compared with 50-300 mg doses of sumatriptan) and reduced peripheral exposure to the coronary vasoconstrictor (5-HT1B) receptor. The notable exception being eletriptan, where an active P-glycoprotein blood-brain barrier efflux system effectively negates these benefits and requires an 80 mg oral dose. Differences in the metabolic balance between hepatic P450 (especially CYP 1A2) and MAO-A inactivation lead to potential drug interactions for all TELs with the oral contraceptive pill (OCP), fluvoxamine and the quinilone antibiotics (with increased triptan levels). An important but complex MAO-A interaction between a metabolite of propranolol and rizatriptan mandates dosage reduction (to 5 mg) for rizatriptan in the presence of propranolol treatment. There is also an absolute contraindication for the concurrent administration of the MAO-A inhibitor moclobemide and rizatriptan. All the new-marketed TELs have potential clinical benefits and were well-tolerated relative to sumatriptan. Both rizatriptan (10 mg) and zolmitriptan (2.5 mg and 5 mg) demonstrate at least equivalent efficacy to sumatriptan 25, 50 and 100 mg, respectively, making them suitable first line agents for moderate or severe migraine headaches. Rizatriptan has the fastest onset of effect of the TELs. Naratriptan would appear to have lower recurrent headache rate than sumatriptan, rizatriptan or zolmitriptan. Therefore, for headaches of long duration and with a tendency to recur naratriptan may be the most appropriate treatment. Thus, knowledge of the metabolic, pharmacokinetic and clinical profiles of the TELs facilitates the selection of a triptan which allows optimisation of the clinical benefits for individual patients, minimising the risk of drug interactions and a minimally effective dose to reduce potential adverse events (AEs).

Effects of sumatriptan on nitric oxide and superoxide balance during glyceryl trinitrate infusion in the rat. Implications for antimigraine mechanisms

Infusion of glyceryl trinitrate (GTN) into patients with migraine precipitates the onset of a migraine attack several hours after completion of the infusion. Using an infusion of GTN into anaesthetised rats, this study investigates the relationship of regional cerebral blood flux rCBF(ldf), cortical nitric oxide (NO) and cortical superoxide concentrations and the effect of sumatriptan on each variable. In saline treated animals, a 30 min infusion of GTN (2 microgram kg(-1) min(-1), i.v.) was found to markedly increase cortical rCBF(ldf) (133+/-3% of baseline) and NO concentrations (141+/-13% of baseline). Superoxide levels exhibited an inverse relationship to NO levels, decreasing below basal to 48+/-14% of baseline. It is hypothesised that high NO levels during GTN infusion may decrease the detectable superoxide due to "leeching" of the superoxide into low level peroxynitrite formation. In the presence of sumatriptan, a decrease below baseline in cortical rCBF(ldf) (82+/-5% of baseline) and NO concentration (64+/-13% of baseline) was observed throughout GTN infusion, although superoxide levels significantly increased above baseline by 105+/-14 nM (p<0.05, ANOVA post hoc LSD test). The mechanism for this action of sumatriptan is unknown but may include; modulation of cell redox state, NO scavenging or direct manipulation of superoxide release.

Influence of the endothelium, nitric oxide and serotonergic receptors on coronary vasomotor responses evoked by ergonovine in conscious dogs

1. The respective contributions of coronary vascular endothelium, nitric oxide (NO) and serotonergic receptors to the effects of ergonovine on large and small coronary arteries were investigated in conscious dogs. 2. In seven dogs with an endothelium intact, ergonovine (30 - 1000 microg, i.v.) induced a biphasic response on large coronary artery with an early and transient vasodilatation (up to +2.9+/-0.5% from 3310+/-160 microm, P<0.01) followed by a sustained vasoconstriction (down to -4.9+/-0.5%, P<0.001) which occurred simultaneously with a sustained increase in coronary blood flow (CBF) (up to +100+/-26% from 28+/-4 ml min(-1), P<0.001). After endothelium removal (balloon angioplasty), the ergonovine-induced vasodilatation was abolished and vasoconstriction potentiated (-6.4+/-0.9% after vs -4.9+/-0.5% before endothelium removal, P<0.01). 3. After blockade of NO synthesis by Nomega-nitro-L-arginine (30 mg kg(-1)) in four other dogs, the early vasodilatation induced by ergonovine was abolished but the delayed vasoconstriction as well as the increase in CBF remained unchanged. 4. Both ketanserin and methiothepin (0.3 mg kg(-1)) abolished the early vasodilatation and reduced the delayed vasoconstriction induced by ergonovine. Ketanserin decreased and methiothepin abolished the reduction in coronary resistance induced by ergonovine. 5. Thus, the complex interactions between vascular endothelium and serotonergic receptors to ergonovine-induced constriction of large coronary arteries might explain the induction of coronary spasms in patients with endothelial dysfunction.

Effects of the novel antimigraine agent, frovatriptan, on coronary and cardiac function in dogs

The effects of frovatriptan (VML 251/SB-209509) on coronary artery function were investigated in isolated coronary arteries from beagle dogs. Low concentrations of frovatriptan produced contraction with -logEC50 7.55 +/- 0.08 (n = 11). The maximal observed contraction attained was 56 +/- 7% of the control 5-hydroxytryptamine (5-HT; 10 microM) response. At high concentrations of frovatriptan (>6 microM), reversal of sumatriptan (10 microM)-induced contractions was noted. In arteries precontracted with the thromboxane mimetic, U46619, frovatriptan produced a bell-shaped concentration-response relation with a maximal response at 600 nM. Concentrations of frovatriptan >2 microM produced marked reversal of tone, with full relaxation of precontracted tissues at 200 microM. In anesthetized, open-chest mongrel dogs, intravenous (n = 5) or intracoronary (n = 5) artery administration of frovatriptan (0.0001-1 mg/kg) had no consistent effect on left ventricular end-diastolic pressure, left end-systolic pressure, cardiac contractility, aortic blood flow, systemic peripheral resistance, coronary blood flow, coronary vascular resistance, mean arterial blood pressure, or heart rate when compared with vehicle (n = 3). Intravenous sumatriptan produced minor effects on blood pressure and heart rate. Intracoronary artery administration of sumatriptan (0.0003 mg/kg) produced an increase in systemic peripheral resistance to 120.5 +/- 8.2% compared with vehicle (97.8 +/- 5.4%; p < 0.05). This dose of sumatriptan also produced a significant increase in coronary blood flow and decrease in coronary vascular resistance. Intravenous administration of sumatriptan produced a dose-related reduction in left ventricular diastolic pressure with a reduction to 58.3 +/- 8.3% and 41.7 +/- 25% of control values observed at 0.3 and 1 mg/kg, respectively; however, administration of sumatriptan by an intracoronary route had no effect. In a model of myocardial infarction, comparable doses of sumatriptan (1.0 mg/kg) or frovatriptan (0.1 mg/kg), in terms of their effect on carotid vascular resistance, had no significant effect on infarct size. Frovatriptan had no effect on coronary blood flow after reperfusion; however, sumatriptan produced a significant reduction in coronary blood flow for < or =3 h. These studies show that frovatriptan has the capability of relaxing coronary arteries in vitro, has no overall effect on cardiac function at rest with no effect on coronary hemodynamics after myocardial infarction, and has a profile superior to that of sumatriptan.