Coronary side-effect potential of current and prospective antimigraine drugs

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.

Pharmacological properties of the naturally occurring Phe-124-Cys variant of the human 5-HT1B receptor: changes in ligand binding, G-protein coupling and second messenger formation

The aim of this study was to analyse whether substitution of phenylalanine in position 124 of the human (h) 5-HT1B receptor by cysteine, a naturally occurring variant of this receptor, modifies not only ligand binding, but also G-protein coupling and second messenger formation. Stably transfected rat C6 glioma cells, which express either the h5-HT1B variant receptor (VR) or the wild-type receptor (WTR) were used. In saturation experiments with [3H]5-carboxamidotryptamine ([3H]5-CT), the maximum binding (Bmax) of the VR amounted to only 60% of that to WTR. In competition experiments with 1 nM [3H]5-CT, the following 5-HT receptor ligands exhibited a higher affinity for the mutant receptor than for the WTR: L-694,247, 5-CT, 5-HT, sumatriptan (agonists listed at decreasing order of potency) and SB-224289 (a selective h5-HT1B receptor inverse agonist with competitive antagonistic properties). In contrast, the mixed 5-HT1B/1D receptor antagonist GR-127935 exhibited equal affinity for both isoforms. The efficacy of L-694,247, 5-CT, 5-HT and sumatriptan in stimulating [35S]GTPgammaS binding (a measure of G protein coupling) to membranes of cells expressing the VR was approximately 50-65% lower compared to membranes of cells expressing the WTR, but their potency was 2.8-3.6-fold higher. SB-224289, which decreased [35S]GTPgammaS binding when given alone, but not GR-127935, was more potent in antagonizing the stimulatory effect of 5-CT on [35S]GTPgammaS binding to membranes expressing the VR compared to membranes expressing the WTR. In whole cells expressing the VR, 5-CT and sumatriptan inhibited the forskolin-stimulated cAMP accumulation 3.2-fold more potently than in cells expressing the WTR. In conclusion, our data suggest that the Phe-124-Cys mutation modifies the pharmacological properties of the h5-HT1B receptor and may account for pharmacogenetic differences in the action of h5-HT1B receptor ligands. Thus, the sumatriptan-induced vasospasm which occurs at low incidence as a side-effect in migraine therapy may be related to the expression of the (124-Cys)h5-HT1B receptor in patients with additional pathogenetic factors such as coronary heart disease.

Contractile responses to sumatriptan and ergotamine in the rabbit saphenous vein: effect of selective 5-HT(1F) receptor agonists and PGF(2alpha)

Contractile responses to ergotamine, sumatriptan and the novel 5-HT(1F) receptor agonists, LY334370 and LY344864 were examined using the rabbit saphenous vein. Ergotamine (pEC(50)=8.7+/-0.06) was 30 fold more potent than 5-hydroxytryptamine (5-HT) (pEC(50)=7.2+/-0.13) and 300 fold more potent than sumatriptan (pEC(50)=6.0+/-0.08) in contracting the rabbit saphenous vein in vitro. The selective 5-HT(1F) receptor agonists, LY334370 or LY344864 (up to 10(-4) M), did not contract the rabbit saphenous vein. The contractile response to ergotamine in this tissue resulted from activation of both alpha(1) and 5-HT(1B/1D) receptors based on the observation that prazosin (10(-6) M), an alpha-adrenoceptor antagonist, and GR127935 (10(-8) M) a 5-HT(1B/1D) receptor antagonist, dextrally shifted the contractile response to ergotamine. In contrast, prazosin (10(-6) M) did not alter contraction to sumatriptan whereas GR127935 (10(-8) M) was a potent antagonist (-log K(B)=10.0) suggesting that sumatriptan-induced contraction of the rabbit saphenous vein was mediated only by activation of receptors similar or identical to 5-HT(1B/1D) receptors. PGF(2alpha) (3x10(-7) M) produced a modest increase (approximately 5.0 - 10.0% maximum PGF(2alpha) contraction) in saphenous vein force. Precontraction with PGF(2alpha) (3x10(-7) M) dramatically augmented the potency and maximal contractile response to sumatriptan (pEC(50)=7.1) and modestly enhanced the contractile potency of ergotamine (pEC(50)=9.0) in the rabbit saphenous vein. However, PGF(2alpha) (3x10(-7) M) only unmasked a contraction to the 5-HT(1F) receptor agonists when concentrations exceeded 10(-5) M, concentrations considerably higher than their 5-HT(1F) receptor affinities. LY334370 (10(-6) M) pretreatment did not alter contraction to either sumatriptan or ergotamine and a higher concentration (10(-5) M) of LY334370 or LY344864 inhibited contraction to sumatriptan. Thus, activation of 5-HT(1F) receptors will not induce vascular contraction (either alone or following modest tone with PGF(2alpha)) or augment contraction to other contractile agonists in the rabbit saphenous vein.

Therapy of Migraine Headache in Cancer Patients

This article reviews how to establish the diagnosis of migraine, the possible differential diagnoses, and the present state of the art of therapy. Emphasis is laid on nonsteroidal antiphlogistic drugs, serotonin receptor agonists (the so called triptans), and antiemetic drugs. The interval therapy consists of beta-blockers, calcium antagonists, antiepileptics, and serotonin receptor antagonists. The pathophysiology is based on the concept of sterile neurogenic inflammation, cortical spreading depression (CSD), and hyperexcitability of the central nervous system (CNS).

Low dose zolmitriptan as a 5-HT neuroendocrine challenge agent in humans

The 5-HT1B/D agonist sumatriptan has been used in a number of studies as a neuroendocrine challenge agent. Whether its neuroendocrine effects are centrally mediated is unclear, however, since sumatriptan shows minimal penetration of the central nervous system. Zolmitriptan shows a greater penetration into the central nervous system than sumatriptan, and has recently been shown to be an effective challenge agent. In order to determine the neuroendocrine, temperature and side effects of a 2.5 mg oral dose of zolmitriptan, 17 healthy volunteers underwent a placebo controlled, repeated measures, double blind neuroendocrine challenge. Zolmitriptan or placebo were administered, and cortisol, growth hormone, prolactin, blood pressure and temperature, were measured over four hours after the dose of zolmitriptan. Zolmitriptan at this dose was well tolerated by all subjects, with minimal side effects and only minor effects on blood pressure. There was a significant increase in serum growth hormone after zolmitriptan compared to placebo, however there were no significant effects on cortisol, prolactin or oral temperature. The neuroendocrine effects of 2.5 mg of orally administered zolmitriptan are similar to previously reported effects of sumatriptan, with minimal side effects.

Effect of naratriptan on myocardial blood flow and coronary vasodilator reserve in migraineurs

BACKGROUND

Migraine drugs can produce adverse cardiac effects. The authors have demonstrated previously that ergotamine can lead to a significant reduction of hyperemic myocardial blood flow, but little is known about the effect of the newer serotonin analogues. Coronary artery constriction caused by serotonin or its analogues is mediated mainly by 5HT2 receptors. The selective 5HT1B/1D agonist naratriptan has no significant activity at 5HT2 receptors; however, like all 5HT1B/1D agonists developed for the acute treatment of migraine, naratriptan could potentially constrict coronary arteries by activation of 5HT1B receptors.

METHODS

The effects on myocardial blood flow of subcutaneous naratriptan 1.5 mg compared with placebo were assessed under resting and hyperemic conditions with PET using oxygen-15 labeled water during two separate visits. This study was a randomized, double-blind, placebo-controlled crossover trial in 34 migraine subjects with no evidence of ischemic heart disease, studied outside a migraine attack.

RESULTS

Naratriptan did not differ significantly from placebo in its effects on resting myocardial blood flow, but did evoke a small, significant fall in hyperemic myocardial blood flow (-13% versus placebo) and an increase in hyperemic coronary resistance (+19% versus placebo) without any signs or symptoms suggestive of myocardial ischemia. Naratriptan did not significantly affect the coronary vasodilator reserve (hyperemic/resting blood flow) compared with placebo.

CONCLUSIONS

These results show that at therapeutic doses, naratriptan exerts only a minor effect on myocardial blood flow, coronary vasodilator reserve, or coronary resistance among subjects with no evidence of ischemic heart disease. These results should not be extrapolated to patients with coronary artery disease, in whom all 5HT1 agonists for migraine are contraindicated.

The potential anti-migraine compound SB-220453 does not contract human isolated blood vessels or myocardium; a comparison with sumatriptan

The mechanistically novel benzopyran derivative SB-220453, which is undergoing clinical evaluation in migraine, exhibits a high affinity for a selective, but not yet characterized, binding site in the human brain. It inhibits nitric oxide release and cerebral vasodilatation following cortical spreading depression as well as carotid vasodilatation induced by trigeminal nerve stimulation in the cat. The aim of our study was to investigate the contractile properties of SB-220453 on a number of human isolated blood vessels (coronary artery, saphenous vein and middle meningeal artery) as well as atrial and ventricular cardiac trabeculae. While sumatriptan induced marked contractions in three blood vessels investigated, SB-220453 was devoid of any effect. In atrial and ventricular cardiac trabeculae, neither SB-220453 nor sumatriptan displayed a positive or negative inotropic effect. Since SB-220453 did not contract the middle meningeal artery, we conclude that potential anti-migraine effects are not mediated via a direct cerebral vasoconstriction. The lack of activity of SB-220453 in coronary artery, saphenous vein and cardiac trabeculae demonstrates that the compound is unlikely to cause adverse cardiac side-effects.

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.

Comparison of the vasoconstrictor effects of the selective 5-HT1D-receptor agonist L-775,606 with the mixed 5-HT1B/1D-receptor agonist sumatriptan and 5-HT in human isolated coronary artery

AIMS

Vasoconstriction in human coronary artery can be mediated via activation of both 5-HT2 and 5-HT1B-receptors. Coronary vasoconstriction is a rare, but potential adverse effect of the antimigraine drug sumatriptan. In order to investigate the receptor population involved we compared the vasoconstrictor effects of sumatriptan (a mixed 5-HT1B/1D-receptor agonist) with those of L-775, 606 (a selective 5-HT1D-receptor agonist) and 5-HT (the endogenous ligand) in human isolated coronary arteries.

METHODS

Coronary arteries were obtained from human hearts removed prior to transplant surgery. Several endothelium denuded ring segments (4 mm in length) were obtained from each artery and mounted for isometric tension recording. Each segment was first exposed to 45 mm KCl and then to 5-HT (1 nm-100 microm ). Concentration-effect curves to L-775,606 (1-(3-(5-(1,2, 4-triazol-4-yl)-1H-indol-3-yl)propyl)-4-(2-(3-fluorophenyl)ethyl)p ipe razine) and sumatriptan were then performed in a consecutive and random manner. The response to repeated application of 5-HT was obtained in separate segments.

RESULTS

Twenty-five segments from seven different coronary arteries were studied. Concentration-effect curves were fitted to the data using nonlinear regression analysis. The maximum contraction for L-775,606 was significantly less than that for sumatriptan with Emax values (% relative to 45 mm KCl=100%) of 30.1+/-4.22 and 41.5+/-2.7, respectively. L-775,606 was significantly (30-fold) less potent than sumatriptan in causing contraction compared with sumatriptan (EC50 values were 6.0 microm and 0.2 microm, respectively). For comparison the Emax value for 5-HT was 77.2% and the EC50 value was 0.2 microm.

CONCLUSIONS

The selective 5-HT1D-receptor agonist L-775,606 has less propensity towards vasoconstriction in human isolated coronary artery (endothelium-denuded) than was mixed 5-HT1B/1D-receptor agonist sumatriptan. The contractions produced were at concentrations where L-775,606 would be expected to occupy 5-HT1B-receptors.

No contractile effect for 5-HT1D and 5-HT1F receptor agonists in human and bovine cerebral arteries: similarity with human coronary artery

1. Using subtype-selective 5-HT1 receptor agonists and/or the 5-HT1 receptor antagonist GR127935, we characterized in vitro the 5-HT receptor that mediates the contraction of human and bovine cerebral arteries. Further, we investigated which sumatriptan-sensitive receptors are present in human coronary artery by reverse-transcriptase polymerase chain reaction (RT-PCR). 2. Agonists with affinity at the 5-HT1B receptor, such as sumatriptan, alniditan and/or IS-159, elicited dose-dependent contraction in both human and bovine cerebral arteries. They behaved as full agonists at the sumatriptan-sensitive 5-HT1 receptors in both species. In contrast, PNU-109291 and LY344864, selective agonists at 5-HT1D and 5-HT1F receptors, respectively, were devoid of any significant vasocontractile activity in cerebral arteries, or did not affect the sumatriptan-induced vasocontraction. The rank order of agonist potency was similar in both species and could be summarized as 5-HT = alniditan > sumatriptan = IS-159 >>> PNU-109291 = LY344864. 3. In bovine cerebral arteries, the 5-HT1 receptor antagonist GR127935 dose-dependently inhibited the vasoconstrictions elicited by both 5-HT and sumatriptan, with respective pA2 values of 8.0 and 8.6. 4. RT-PCR studies in human coronary arteries showed a strong signal for the 5-HT1B receptor while message for the 5-HT1F receptor was weak and less frequently detected. Expression of 5-HT1D receptor mRNA was not detected in any sample. 5. The present results demonstrate that the triptan-induced contraction in brain vessels is mediated exclusively by the 5-HT1B receptor, which is also present in a majority of human coronary arteries. These results suggest that selective 5-HT1D and 5-HT1F receptor agonists might represent new antimigraine drugs devoid of cerebro- and cardiovascular effects.

Pathophysiology of migraine--new insights

Current theories propose that the primary dysfunction in migraine occurs within the CNS and that this evokes changes in blood vessels within pain-producing intracranial meningeal structures that give rise to headache pain. Migraine is now thought of as a neurovascular disorder. It has been proposed that genetic abnormalities may be responsible for altering the response threshold to migraine specific trigger factors in the brain of a migraineur compared to a normal individual. The exact nature of the central dysfunction that is produced in migraineurs is still not clear and may involve spreading depression-like phenomena and activation of brain stem monoaminergic nuclei that are part of the central autonomic, vascular and pain control centers. It is generally thought that local vasodilatation of intracranial extracerebral blood vessels and a consequent stimulation of surrounding trigeminal sensory nervous pain pathways is a key mechanism underlying the generation of headache pain associated with migraine. This activation of the 'trigeminovascular system' is thought to cause the release of vasoactive sensory neuropeptides, especially CGRP, that increase the pain response. The activated trigeminal nerves convey nociceptive information to central neurons in the brain stem trigeminal sensory nuclei that in turn relay the pain signals to higher centers where headache pain is perceived. It has been hypothesized that these central neurons may become sensitized as a migraine attack progresses. The 'triptan' anti-migraine agents (e.g. sumatriptan, rizatriptan, zolmitriptan naratriptan) are serotonergic agonists that have been shown to act selectively by causing vasoconstriction through 5-HT1B receptors that are expressed in human intracranial arteries and by inhibiting nociceptive transmission through an action at 5-HT1D receptors on peripheral trigeminal sensory nerve terminals in the meninges and central terminals in brain stem sensory nuclei. These three complementary sites of action underlie the clinical effectiveness of the 5-HT1B/1D agonists against migraine headache pain and its associated symptoms.

The scientific basis of medication choice in symptomatic migraine treatment

With the rapid advances in the treatment of acute attacks of migraine in the last few years and a number of new treatments, has come the practical clinical problem of comparing emerging acute attack therapies alone and with regard to current treatments. Acute migraine therapies can usefully be regarded as non-specific and specific, from the perspective of migraine, since some medicines, such as aspirin or paracetamol, are used to treat pain more broadly. In this review I will compare both non-specific and specific compounds. To some extent the introduction into trial then clinical use of sumatriptan, the first of the 5HT1B/1D agonists or triptans, brought new standards in both clinical trial design, and execution and clinical outcome. Thus sumatriptan has become the de facto gold standard and will be thus employed here. To be practical the discussion of the new triptans will be limited to those available widely, naratriptan, rizatriptan and zolmitriptan. There are two broad issues when comparing treatments: what end-point should be considered and then, how can different compounds be compared with respect to that end-point. In terms of end-points those used here relate to pain relief because they have been collected robustly in the clinical studies and, fortunately, rapid pain relief is what patients questioned in population-based studies rate highest in an acute attack medicine. Headache pain has been rated on a scale of nil, mild, moderate and severe and success rated as either a response, nil or mild pain, or headache free, nil pain, at two or four hours. The ideal comparison of the triptans would be a randomized controlled clinical trial directly comparing the medicines in each case. Given that these are not available for all the compounds and the well characterised placebo response in acute migraine studies, summary measures have been developed to express the differences between compounds to try and adjust for the varying placebo effect. The two most widely used are the therapeutic gain, response on active medication minus response on placebo, and the number-needed-to-treat (NNT). The NNT is the reciprocal of the therapeutic gain as a proportion. The strengths and weaknesses of this approach will be discussed, including the importance of the calculation of confidence intervals. It can be concluded that our current instruments are rather blunt and patient preference needs much greater study.

The biology of serotonin receptors: focus on migraine pathophysiology and treatment

Serotonin receptors are highly heterogeneous and they have been regrouped within seven different families (5-HT1-5-HT7). With the exception of the 5-HT3 which is a ligand-gated ion channel, all others are G-protein coupled receptors with each family sharing structural, pharmacological and transductional characteristics. 5-HT receptors have been implicated in the regulation of several psychiatric and neurological disorders related to serotonergic neurotransmission, and specific receptor subtypes have recently been associated with either the pathogenesis or the treatment of migraine headache. In this respect, activation of vascular 5-HT2B and/or 5-HT7 receptors, possibly as a consequence of the sudden rise in 5-HT levels reported at the onset of a migraine attack, would hypothetically result in dilation of cerebral blood vessels and concomitant activation of sensory trigeminovascular afferents, hence initiating the manifestation of head pain. At this stage in the migraine process, activation of specific subtypes of 5-HT1 receptors has proven clinically effective in relieving migraine pain. Neural 5-HT1D and/or 5-HT1F receptors localized pre-junctionally on trigeminovascular afferents appear to mediate the triptan-induced inhibition of the neurogenic inflammatory response, with possible additional sites of action for brain penetrant 5-HT1 receptor agonists in inhibiting the transmission of pain centrally. In contrast, activation of vascular 5-HT1B receptors would constrict meningeal vessels hence recovering their pre-migraine diameter. The recent availability of subtype selective 5-HT1D and 5-HT1F receptor agonists should allow a further test of the neural/vascular hypothesis and could possibly lead to antimigraine drugs with a safer cardiovascular profile.

Human isolated coronary artery contraction to sumatriptan: a post hoc analysis

A post hoc analysis was performed on concentration response curves to sumatriptan in 62 human isolated coronary arteries. We determined whether donor-related clinical characteristics (age, sex, cause of death) and properties of the coronary artery (functional endothelial integrity, muscle mass) were related to the potency and efficacy of sumatriptan in contracting the human isolated coronary artery. The efficacy of sumatriptan was inversely related to the functional integrity of the vessel endothelium. Thus, contrary to expectation, coronary artery constriction to sumatriptan seems to be more pronounced in patients with nondiseased coronary arteries where the endothelium is intact. Nevertheless, in view of the high coronary reserve in these patients, myocardial ischemia after the use of sumatriptan is unlikely to occur, whereas in patients with coronary artery disease even a small contraction may be deleterious.

Migraine: a comprehensive review of new treatment options

Headaches are among the most common complaints reported to health care professionals and are classified by the International Headache Society as migraine, tension-type, or cluster, with additional subtypes. Classification and etiology of headache should be determined after thorough review of the patient's history. Once diagnosed, migraine can be treated by preventive or abortive measures. Recent developments add new options, including availability of drugs for intranasal administration (sumatriptan, dihydroergotamine) and 5-HT1B/1D agonists (rizatriptan, zolmitriptan, naratriptan, eletriptan). Although placebo-controlled trials are available, few comparative clinical trials of these agents have been conducted; however, important pharmacologic, pharmacokinetic, and clinical differences exist among the drugs.

Effects of subcutaneous naratriptan on systemic and pulmonary haemodynamics and coronary artery diameter in humans

Naratriptan, an effective antimigraine agent, is a selective 5-hydroxytryptamine (5-HT1 )-receptor agonist with a pharmacologic profile similar to that of sumatriptan. The object of this study was to assess the haemodynamic effects of naratriptan in a clinical model previously applied to sumatriptan. Cardiac haemodynamics and coronary artery diameter were measured at baseline and after subcutaneous injections of placebo and naratriptan (1.5 mg, s.c.) in 10 patients undergoing diagnostic cardiac catheterisation. No statistically significant change in mean coronary artery diameter was observed after naratriptan [95% confidence interval (CI), -0.27-0.11 mm: p = 0.37]. Naratriptan injection was associated with statistically significant increases in systolic arterial pressure (95% CI, 7.6-22.0 mm Hg; p = 0.0015), total systemic vascular resistance (95% CI, 74-253 dyn/s/cc; p = 0.003), pulmonary artery systolic pressure (95% CI, 2.0-6.9 mm Hg; p = 0.003), pulmonary vascular resistance (95% CI, 3-34 dyn/s/cc; p = 0.025), and pulmonary artery wedge pressure (95% CI, 1.9-2.4 mm Hg; p = 0.009). Naratriptan, a selective 5-HT1-receptor agonist, caused a vasopressor response in the systemic and pulmonary arterial circulations but was not associated with coronary artery vasoconstriction.

Pharmacological aspects of experimental headache models in relation to acute antimigraine therapy

The last decade has witnessed a tremendous progress in the acute therapy of migraine, with sumatriptan, belonging to a new class of drugs, now known as 5-HT(1B/1D/1F) receptor agonists, leading the way. The undoubted success of sumatriptan stimulated the development of new triptans as well as other suitable pharmacological tools and experimental models to probe into complex migraine mechanisms. In this review, we discuss the main experimental models for migraine, against the background of the disease pathophysiology and 5-HT receptors considered most important for migraine therapy. We believe that the use of these migraine models will provide even better treatment for migraine patients in the next millennium.

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.

Acute management of migraine: triptans and beyond

Migraine is a paroxysmal disorder characterized by attacks of headache, nausea, vomiting, photophobia and phonophobia, and malaise. This review summarizes new treatment options for the therapy of acute attacks. Sumatriptan was the first specific serotonin-1B/D agonist for the treatment of acute migraine attacks. Apart from the oral and subcutaneous formulation, it is also available as nasal spray and suppository. The other new migraine drugs zolmitriptan, naratriptan, rizatriptan and eletriptan differ in their pharmacological profiles, which translates into minor differences in efficacy, headache recurrence and side-effects. Importantly, in clinical practice individual patients may show a preference for one treatment over another. New drugs in migraine treatment include substance-P antagonists, nitric oxide synthetase inhibitors and calcitonin gene-related peptide antagonists.

Characterisation of 5-HT receptors in human coronary arteries by molecular and pharmacological techniques

5-Hydroxytryptamine (5-HT) can produce both vasoconstrictor and vasorelaxant effects in human coronary arteries and the response to 5-HT can be influenced by the presence of disease. The aim of the present study was to elucidate the 5-HT receptor subtypes responsible for mediating 5-HT-evoked contraction of human coronary arteries using pharmacological, molecular and immunocytochemical approaches. Normal human coronary arteries, with intact endothelium, were mounted in tissue baths, and the vascular responses to 5-HT and 5-HT receptor agonists were studied. The effects of 5-HT1 and 5-HT2 receptor antagonists on these responses were also studied. Expression of messenger ribonucleic acid (mRNA) encoding different 5-HT receptors in human coronary arteries, atrium, ventricle wall and epicardium was determined using reverse transcriptase-polymerase chain reaction (RT-PCR) and Southern blot analysis. The expression of 5-HT1B or 5-HT1D receptor protein was studied using subtype selective antibodies and standard immunocytochemical techniques. The rank order of 5-HT receptor agonist potency in causing vasoconstriction was 5-carboxamido tryptamine, (5-CT) > zolmitriptan = BW183C91 (N10-desmethyl zolmitriptan) = alpha-methyl-5-hydroxytryptamine (alpha-CH3-5-HT) = 5-HT = sumatriptan > 2-methyl-5-hydroxytryptamine (2-CH3-5-HT) = 8-hydroxy-DPAT (8-OH-DPAT). Alpha-CH3-5-HT, 5-CT, 5-HT, zolmitriptan and BW 183C91 were significantly more potent (approximately 3-fold) than sumatriptan and 2-CH3-5-HT, which in turn were more potent than 8-OH-DPAT. Ketanserin and methiothepin (5-HT2 and 5-HT1 receptor antagonists, respectively) caused parallel rightward shifts of the concentration-effect curves to alpha-CH3-5-HT or 5-CT, respectively, without changing the maximum contractile response. In human coronary arteries, atrium. ventricle and epicardium. RT-PCR products corresponding to the human 5-HT2A, 5-HT1B and 5-HT1F receptors were expressed in high levels, mRNAs coding for 5-HT7, 5-HT1A and 5-HT1D receptors were only weakly expressed. No 5-HT1F receptor mRNA was detected. In coronary arteries there was a differential expression of 5-HT1B versus 5-HT1D receptor mRNAs, with 5-HT1B mRNAs being found in greater abundance. Dense 5-HT1B-immunoreactivity was detected on smooth muscle layer within coronary artery, however, 5-HT1D-immunoreactivity was not detected. It is concluded that 5-HT-evoked contraction of human coronary arteries is most probably mediated via the activation of both 5-HT1B and 5-HT2A receptors.

Canine external carotid vasoconstriction to methysergide, ergotamine and dihydroergotamine: role of 5-HT1B/1D receptors and alpha2-adrenoceptors

The antimigraine drugs methysergide, ergotamine and dihydroergotamine (DHE) produce selective vasoconstriction in the external carotid bed of vagosympathectomized dogs anaesthetized with pentobarbital and artificially respired, but the receptors involved have not yet been completely characterized. Since the above drugs display affinity for several binding sites, including alpha-adrenoceptors and several 5-HT1 and 5-HT2 receptor subtypes, this study has analysed the mechanisms involved in the above responses. Intracarotid (i.c.) infusions during 1 min of methysergide (31-310 microg min(-1)), ergotamine (0.56-5.6 microg min(-1)) or DHE (5.6-31 microg min(-1)) dose-dependently reduced external carotid blood flow (ECBF) by up to 46+/-4, 37+/-4 and 49+/-5%, respectively. Blood pressure and heart rate remained unchanged. The reductions in ECBF by methysergide were abolished and even reversed to increases in animals pre-treated with GR127935 (10 microg kg(-1), i.v.). The reductions in ECBF by ergotamine and DHE remained unchanged in animals pre-treated (i.v.) with prazosin (300 microg kg(-1)), but were partly antagonized in animals pre-treated with either GR127935 (10 or 30 microg kg(-1)) or yohimbine (1000 microg kg(-1)). Pre-treatment with a combination of GR127935 (30 microg kg(-1)) and yohimbine (1000 microg kg(-1)) abolished the responses to both ergotamine and DHE. The above doses of antagonists were shown to produce selective antagonism at their respective receptors. These results suggest that the external carotid vasoconstrictor responses to methysergide primarily involve 5-HT1B/1D receptors, whereas those to ergotamine and DHE are mediated by 5-HT1B/1D receptors as well as alpha2-adrenoceptors.

Safety trial with the 5HT1B/1D agonist avitriptan (BMS-180048) in patients with migraine who have experienced pressure, tightness, and/or pain in the chest, neck, and/or throat following sumatriptan

We investigate whether symptoms of pressure, tightness, and/or pain in the chest, neck, and/or throat after administration of the 5HT1B/1D agonist avitriptan were associated with objective impairment of the myocardial function on 12-lead electrocardiogram (ECG), continuous ECG (Holter) monitoring, and echocardiography. Migraine sufferers who in two-thirds of all attacks treated with sumatriptan had experienced chest/throat/neck symptoms were chosen for study. Baseline measures included vital signs, a 12-lead ECG and an echocardiogram. Patients (n = 51) who had no clinically significant abnormality at baseline received a high dose (150 mg) of avitriptan orally outside of a migraine attack. If pressure, tightness, and/or pain in the chest, neck, and/or throat occurred, an ECG was obtained, and a repeat echocardiogram was done while the symptoms were present in order to monitor for impairment of myocardial function. If symptoms of these types did not occur within 60 min after administration of the study drug, a second echocardiogram was obtained. Forty-five patients (88%) reported at least one adverse event and 23 (45%) experienced pressure, tightness, and/or pain in the chest, neck, and/or throat after administration of avitriptan. No clinically significant myocardial abnormalities were observed in any patients, even in those who had experienced the targeted symptoms. No other serious adverse event occurred. We concluded that the typical 5HT1B/1D agonist-induced chest/throat/neck symptoms are most unlikely to be of cardiovascular origin.

BMS-181885, a 5-HT1B/1D receptor ligand, in experimental models predictive of antimigraine activity and coronary side-effect potential

Many acutely acting antimigraine drugs have the ability to constrict porcine arteriovenous anastomoses as well as the human isolated coronary artery. These two experimental models seem to serve as indicators, respectively, for the therapeutic and coronary side-effect potential of the compounds. Using these two models, we have investigated the effects of BMS-181885 (3-[3-[4-(5-methoxy-4-pyrimidyl)-1-piperazinyl]propyl]-5-(1,2-dioxo-4-me thyl-3-cyclobuten-3-yl)amino-1H-indole), a 5-HT1B/1D receptor ligand. In anaesthetised pigs, BMS-181885 (10, 30, 100 and 300 microg kg(-1)) decreased the total carotid blood flow and conduction, exclusively at the expense of the arteriovenous anastomotic fraction as the capillary fraction did in fact increase. The highest dose (300 microg kg(-1)) produced a reduction of 52+/-6% from the baseline arteriovenous anastomotic flow. When carotid haemodynamic changes after a single 100 microg kg(-1)dose of BMS-181885 or sumatriptan were studied at different time-points, BMS-188185 had a longer duration of action. Both BMS-181885 (pD2:7.9+/-0.1; Emax:9+/-3% of the contraction to 100 mM K+) and sumatriptan (pD2:6.3+/-0.1; Emax:28+/-8% of the contraction to 100 mM K+) contracted the human isolated coronary artery. The above results suggest that (i) the longer-lasting vasoconstrictor action of BMS-181885 on porcine carotid arteriovenous anastomoses may be related to its reported slow dissociation from 5-HT1B/1D receptor, and (ii) BMS-181885 should be able to abort migraine headaches in patients. It will be interesting to find out whether these properties are clinically important so that the drug exhibits less headache recurrence and coronary side-effects than sumatriptan.