Anti-Migraine agents

Cluster headache, an excruciating, unilateral headache usually accompanied by conjunctival injection and lacrimation, can occur episodically or chronically, and can be difficult to treat. Existing effective treatments may be underused because of underdiagnosis of the syndrome. Oxygen and sumatriptan have been demonstrated to be effective in the acute treatment of cluster headaches. Verapamil has been shown to be effective for prophylaxis. For cluster headache completely refractory to all treatments, surgical modalities and newer interventions such as the implantation of stereotactic electrodes may be useful. Patients should be encouraged to avoid possible triggers such as smoking or alcohol consumption, especially during the duster period. The intensity of duster headache pain leads to ethical concerns among researchers over the use of placebo, making randomized controlled trials difficult. As new technology and genetic studies clarify the etiology of duster headache, it is possible that more specific therapies will emerge.

BACKGROUND : The physician treating patients with migraine is now able to choose from among seven triptans-almotriptan, eletriptan, frovatriptan, naratriptan, rizatriptan, sumatriptan and zolmitriptan. These differ, to greater or lesser degrees, on a range of clinical attributes important for treatment selection. OBJECTIVE : To outline the basic principles of Multiattribute Decision Making (MADM) and describe how one such method-TOPSIS (Technique for Order Preference by Similarity to the Ideal Solution)-can be applied to evaluate the currently available triptans. METHODS : In an example application, summary data from a recent meta-analysis of 53 published and unpublished placebo-controlled trials of the oral triptans were combined in TOPSIS models with computer-generated attribute importance weights representing the entire range of possible values, That is, the relative performance of the triptans was explored across all logically possible combinations of relative importance of the treatment attributes available from the meta-analysis, and uncertainty was assessed based on the confidence intervals from the meta-analysis. RESULTS : When compared across the entire range of values for relative attribute importance, almotriptan, eletriptan and rizatriptan were more similar to a hypothetical ideal triptan and were more likely to appear in the top three closest to the hypothetical ideal, than were naratriptan, sumatriptan, and zolmitriptan. CONCLUSION : Using the TOPSIS model, almotriptan, eletriptan and rizatriptan were more likely to appear in the top three closest to the hypothetical ideal triptan.

Probably because of its relative rarity as primary headache, there are few well-controlled clinical trials on cluster headache (CH) patients. Due to the severity of the pain, the placebo response in CH has been considered to be small. During the eighties the first double-blind, placebo-controlled trials were reported, and placebo responses demonstrated. Here we review the placebo response in CH trials in order to assess its magnitude and consider how future studies can be optimized. Six trials were identified with a double-blind, placebo-controlled, cross-over design testing treatments of acute CH. For those with a primary endpoint set to no or mild headache the placebo responses varied from 7 to 42%. In five of seven prophylactic trials, using a double-blind, placebo-controlled, parallel-group design, the placebo was merely used to set a baseline for comparison. The placebo responses were reported in only two trials. Here the response varies from 14 to 43%, the lowest value was reported using the strict endpoint; cessation of headache attacks. We conclude that a placebo response exists in trials of drugs on CH patients. Furthermore, this placebo response is of the same magnitude as that seen in migraine studies. We recommend the use of IHS guidelines when designing new trials. The possibility of a genuine biological mechanism responsible for the placebo response is discussed.

Int J Clin Pract. 1998 Nov-Dec;52(8):566-70.
New anti-migraine drugs: present and beyond the millennium.
Limmroth V, Diener HC.
Department of Neurology, University of Essen, Germany.

A fast growing new class of anti-migraine drugs has recently been introduced for the acute treatment of migraine: the serotonin (5-HT) 1B/D-agonists. Since the introduction of its first representative, sumatriptan, in 1993, several new compounds of this class have been or are about to be approved. The following review introduces this class of compounds and focuses on indications, differences, advantages and disadvantages of each member. It further discusses new indications of established drugs for the use in migraine, including prophylaxis. For the use of analgesics and ergotamine, the reader is referred to recent reviews.

The major finding of this analysis is that acute anti-migraine agents (e.g., ergots, sumatriptan) share high affinity for 5-HT1D receptors. This receptor appears to be present in certain intracranial blood vessels. It is also found on nerve terminals where it inhibits the release of 5-HT and other neurotransmitters. Theoretically, 5-HT1D receptor agonists may acutely inhibit the release of vasoactive and/or pain-inducing substances in the perivascular space. Conceivably, drugs acting at this receptor would stop the progression of this perivascular process. In contrast, a number of prophylactic anti-migraine drugs share a relatively high affinity for 5-HT2 receptors in human brain. Although this receptor is also found in certain blood vessels, it is present throughout the nervous system. The receptor appears to mediate neuronal depolarizations at the cellular level. No hypothesis, at present, readily explains the effectiveness of prophylactic anti-migraine drugs based on this receptor. These data offer a novel approach to the analysis of anti-migraine agents. Drugs could be selected for use in clinical migraine studies based on their selectivity for a specific 5-HT receptor subtype. "Pure" drugs could be chosen which would essentially limit the number of possible sites of action for the drugs. For example, an agent which displays both high affinity and selectivity for 5-HT1D receptors could be clinically evaluated. Its effectiveness, or lack thereof, would indicate the importance of the specific 5-HT receptor site in the pathogenesis of migraine. Further attempts to determine a common mechanism of action for effective anti-migraine agents should facilitate the elucidation of the pathogenesis of this neurological syndrome.