Treatment of migraine with BMS180048: response at 2 hours. North American BMS180048 Study Group

Is the Generally Held View That Intravenous Dihydroergotamine Is Effective in Migraine Based on Wrong "General Consensus" of One Trial? A Critical Review of the Trial and Subsequent Quotations

BACKGROUND

The claim that parenteral dihydroergotamine (DHE) is effective in migraine is based on one randomized, placebo-controlled, crossover trial from 1986. The aim of this review was to critically evaluate the original article. It was also found to be of interest to review quotes concerning the results in the more than 100 articles subsequently referring to the article.

METHODS

The correctness of the stated effect of intravenous DHE in the randomized clinical trial (RCT) was first critically evaluated. Then, Google Scholar was searched for references to the article and these references were classified as to whether they judged the reported RCT as positive or negative.

RESULTS

The design of the RCT, with a crossover within one migraine attack, only allows evaluation of the results for the first period and the effect of DHE and placebo were quite comparable. About 151 references were found for the article in Google scholar. Among the 95 articles with a judgment on the efficacy of intravenous DHE in the RCT, 90 stated that DHE was effective or likely effective whereas only 5 articles stated that DHE was ineffective.

CONCLUSIONS

Despite a "negative" RCT, authors of subsequent articles on the efficacy of parenteral DHE overwhelmingly reported this RCT as "positive." This is probably due to the fact that the authors concluded in the abstract that DHE is effective, and to a kind of "wrong general consensus."

Placebo Effects in Oral Triptan Trials: the Scientific and Ethical Rationale for Continued use of Placebo Controls

The aim of this study was to determine the characteristics of placebo effects in acute migraine treatment trials of triptans performed over 12 years and assess whether the use of placebo controls in trials of acute migraine treatment remains ethically and scientifically appropriate. We conducted a search for all controlled trials published in English between January 1991 and April 2002 in which adult subjects with migraine were randomly assigned to receive an oral triptan or placebo for the acute treatment of a migraine attack. Thirty-one trials met our criteria for inclusion. Placebo results for each study and pooled placebo results were calculated for the endpoints of headache response, pain-free response and adverse events. Heterogeneity was assessed using the Q statistic, and meta-regression using prespecified covariates was performed to investigate heterogeneity. The study results show a significant degree of heterogeneity. Efforts to explain heterogeneity with available data were not successful, with the exception of adverse event rates to placebo, for which study location (Europe vs. North America) partially explained differences in study results. AE rates were lower in European studies than in North American studies. Across all studies, the mean proportion of subjects who experienced a treatment response at two hours to placebo was 28.48 + 8.73% (range 17-50%). The mean proportion of subjects who experienced an adverse event to placebo was 23.40 + 14.05% (range 4.86-74%). The mean proportion of subjects who experienced a pain-free response to placebo at two hours was 6.08 + 4.43% (range 5-17%). Results of studies allowing use of prophylaxis did not differ significantly from those that did not allow prophylaxis. Placebo effects appear to be enhanced in studies involving children and adolescents. In contrast to an earlier, smaller review, our results do not suggest that randomization ratios influence placebo rates. We conclude that placebo effects in published trials of acute migraine medications are highly variable and often substantial. This variability in placebo response means that active control equivalence trials or the use of historical controls will not provide adequate proof of the safety or efficacy of new drugs, and will not differentiate between drugs that are active vs. placebo but of unknown efficacy relative to each other. The potential for approval of ineffective drugs, inability to compare results of studies performed in different locations, and poor characterization of the tolerability and safety profiles of new drugs represent a greater danger to migraineurs than does the limited-duration use of placebo in carefully monitored clinical trials of consenting subjects. These observations support the view that the inclusion of a placebo group remains of major scientific and ethical importance in trials of migraine medications.

Advances in pharmacological treatment of migraine

Migraine is a paroxysmal disorder with attacks of headache, nausea, vomiting, photo- and phonophobia and malaise. This review summarises new treatment options both for the therapy of the acute attack as well as for migraine prophylaxis. Analgesics like aspirin or non-steroidal anti-inflammatory drugs (NSAIDs) are effective in treating migraine attacks. Few controlled trials were performed for the use of ergotamine or dihydroergotamine. These trials indicate inferior efficacy compared with serotonin (5-HT(1B/D)) agonists (triptans). The triptans (almotriptan, eletriptan, frovatriptan, naratriptan, rizatriptan, sumatriptan and zolmitriptan), are highly effective. They improve headache as well as nausea, photo- and phonophobia. The different triptans show only minor differences in efficacy, headache recurrence and adverse effects. The knowledge of their different pharmacological profile allows a more specific treatment of the individual migraine characteristics. Migraine prophylaxis is recommended, when more than three attacks occur per month, if attacks do not respond to acute treatment or if side effects of acute treatment are severe. Substances with proven efficacy include the beta-blockers metoprolol and propranolol, the calcium channel blocker flunarizine, several 5-HT antagonists and amitriptyline. Recently anti-epileptic drugs (valproic acid, gabapentin, topiramate) were evaluated for the prophylaxis of migraine. The use of botulinum toxin is under investigation.

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.

Pharmacokinetics and pharmacodynamics of avitriptan during intravenous administration in healthy subjects

Avitriptan, a selective 5-HT1-like receptor agonist, is an effective compound for the treatment of migraine headaches with a prolonged duration of response. A double-blind, placebo-controlled, parallel-group, ascending-dose study in 24 healthy subjects was designed to assess the safety, tolerance, pharmacokinetics, and pharmacodynamics of avitriptan. This antimigraine drug was administered as two consecutive constant-rate IV infusions at three dose levels (12.7, 25.3, and 38.0 mg), which were targeted to produce plasma concentrations in and above the therapeutic range. The best fitting of the plasma concentration-time data was obtained by using a triexponential function yielding a terminal t1/2 of 8 hours. The areas under the plasma concentration versus time curves were proportional to dose, indicating linear pharmacokinetics. Moreover, the clearance and steady-state volume of distribution values were independent of the dose. The change in pulse rate and supine systolic and diastolic blood pressure was determined as pharmacodynamic effects of avitriptan. A "threshold log-linear" model, which accounts for the linear increase in pharmacodynamic effect with the log of plasma concentrations when the latter was higher than a certain threshold value, adequately described the pharmacodynamic data. The threshold plasma drug concentrations for the pulse rate and the diastolic and systolic blood pressure were 14, 74, and 161 ng/ml, respectively. Overall, avitriptan has consistent, linear pharmacokinetics and increases systolic and diastolic blood pressure in a predictable manner at a higher plasma concentration. However, this drug does not produce a significant change in pulse rate at the dose levels (12.7-38 mg) evaluated in this study.

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.