Published and not fully published double-blind, randomised, controlled trials with oral naratriptan in the treatment of migraine: a review based on the GSK Trial Register
© The Author(s) 2011
Received: 29 January 2011
Accepted: 5 March 2011
Published: 25 March 2011
Naratriptan 2.5 mg is now an over-the-counter drug in Germany. This should increase the interest in drug. The GSK Trial Register was searched for published and unpublished double-blind, randomised, controlled trials (RCTs) concerning the use of naratriptan in migraine. Only 7 of 17 RCTs are published in full. Naratriptan 2.5 mg is superior to placebo for acute migraine treatment in 6 RCTs, but inferior to sumatriptan 100 mg and rizatriptan 10 mg in one RCT each. This dose of naratriptan has no more adverse events than placebo. Naratriptan 1 mg b.i.d. has some effect in the short-term prophylactic treatment of menstruation-associated migraine in 3 RCTs. In 2 RCTs, naratriptan 2.5 mg was equivalent to naproxen sodium 375 mg for migraine-related quality of life. Naratriptan 2.5 mg (34% preference) was superior to naproxen sodium 500 mg (25% preference). Naratriptan 2.5 mg is better than placebo in the acute treatment of migraine. The adverse effect profile of naratriptan 2.5 mg is similar to that of placebo. The efficacy of naratriptan 2.5 mg versus NSAIDs is not sufficiently investigated. Naratriptan, when available OTC is a reasonable second or third choice on the step care ladder in the acute treatment of migraine.
In Germany, the 5-hydroxytryptamine (5-HT)1B/1D receptor agonist naratriptan is an over-the-counter (OTC) drug, most likely because of its excellent tolerability [1–3]. The time to maximum blood concentration is 2 h for oral naratriptan, and 1.5 h for oral sumatriptan [2, 4]. The oral bioavailability of naratriptan is 74%, and much higher than the 14% availability of sumatriptan . The elimination half-lives of naratriptan and sumatriptan are 5.5 and 2 h, respectively . Naratriptan 2.5 mg tablets have a placebo-like tolerability profile and are associated with a low incidence of headache recurrence . Thus, the 2.5-mg dose offers some advantages over other 5-HT1B/1D agonists, and naratriptan has been called the “gentle triptan” .
In 1998, the Ethics Subcommittee of the International Headache Society  stated that the “responsibility for publication cannot be separated from the ethical responsibility of the investigator”. The Subcommittee agreed that “scientists have an ethical obligation to submit creditable research results for publication, and should not enter into agreements that interfere with their control over the decision to publish.” As a general rule, every methodologically sound, randomised, controlled trial should be published to allow an evaluation of the results; publication solely as an abstract or in non-peer-reviewed supplements is unacceptable .
Recently, I reported on six unpublished randomised controlled trials (RCTs) with sumatriptan . These RCTs were found in the GlaxoSmithKline (GSK) Trial Register, and I became aware of unpublished RCT with naratriptan. Because naratriptan is now becoming an OTC drug in some countries, a review of all RCTs is relevant. In the present review of 17 double-blind, randomised, controlled trials (RCTs) in the naratriptan part of the GSK Trial Register, it was remarkable that less than half of these RCTs were fully published in peer-reviewed journals.
Overview of 17 randomised, controlled trials with oral naratriptan for migraine treatment found in the GSK Trial Register (http://www.gsk-clinicalstudyregister.com/)
Drugs used [reference] (protocol code in GSK register)
Number of centers
Total number of patients (study design)
Na 2.5 mg vs. naproxen sodium (NS) 275 mg  [S2WA4003]
Na and NS had similar effect on MRQL
Na 2.5 mg vs. NS 275 mg  [S2WA4004]
Na and NS had similar effect on MRQL
Na 2.5 mg vs. NS 500 mg  [S2W40010]a
Preference: Na (34%) > NS (26%)c
Na 2.5 mg vs. PL in mild MAM  [S2W40031]
Na (58% headache relief) > PL (30% headache relief)
Na 1 mg b.i.d. vs. placebo for MAM  [S2W40012]
Without MAM: Na 38% > PL 29%
Na 1 mg b.i.d. vs. PL  [S2W40024]
Without MAM: Na 34% > PL 24%
Na 0.1, 0.25, 1.0, 2.5 mg vs. PL  [S2WA3001]
Na 1 mg (50%) and 2.5 mg (60%) > PL (34%) for headache relief at 4 h
Na 0.25, 1.0, and 2.5 mg vs. PL  [S2WA3003]
Na 1.0 mg (57%) and 2.5 mg (68%) > PL (33%) for headache relief after 4 h
Na 0.25, 1.0, and 2.5 mg vs. placebo in adolescent migraine  [S2WA3012]
Na 0.25 mg (72%), 1.0 mg (67%) and 2.5 mg (64%) were similar to PL (65%) for headache relief after 4 h
Na 2.5 mg vs. PL in pt not responding to sumatriptan  [S2WA4002]
206 (382) (P)b
Na (47%) > PL (20%) for headache relief after 4 h
Na 2.5 mg b.i.d. vs. PL in transformed migraine  [S2WA4005]
Na (13%) similar to PL (17%) for no headache on days 13 and 14.
Na 1 mg and 2.5 mg b.i.d. vs. PL in MAM  [S2WA4006]
Median MAM over 4 menstruation: PL = 4, 1 mg = 2, 2.5 mg = 3. Na 1.0 mg < PL (p = 0.011)
Na 2.5 mg vs. sumatriptan 100 mg in recurrence prone patients  [S2WB3011]
24 h overall efficacy: Na (40%) similar to sumatriptan (35%)
Na 0.1 mg, 0.25 mg, 1.0 mg, and 2.5 mg vs. sumatriptan 100 mg vs. placebo  [S2WB3002]
1,141 (942) (P)c
Na 1.0 mg (52%) and 2.5 mg (66%) > PL (27%) for headache relief at 4 h, sumatriptan (76%) was superior to all Na doses
Na 2.5 mg vs. sumatriptan 50 mg in patients who relapse from sumatriptan (100 mg orally or 6 mg subcutaneously)  [S2WB4001]
Satisfaction with overall effectiveness: very satisfied or satisfied: Na (52%) similar to sumatriptan (48%)
Na 5 mg and 10 mg vs. placebo  [S2WB2003]
Headache relief at 4 h: Na 5 mg (89%) and 10 mg (72%) > PL (33%)
Na 1, 2.5, 5, 7.5, and 10 mg vs. sumatriptan 100 mg and vs. PL  [S2WB2004]
For headache relief at 4 h all doses of Na (64%, 63%, 65%, 80%, and 80%) were superior to PL (39%). Na 7.5 mg and 10 mg were similar to sumatriptan 100 mg (80%), which was superior to Na 1, 2.5, and 5 mg
The median number of participating centers per RCT was 51 (range 10–152). In these 17 RCTs, the median number of patients was 236 (range 168–1,141). Seven RCTs [11, 14, 15, 17, 19, 20, 23] were fully published in a peer-reviewed journal. Ten RCTs [12–17, 19, 21, 23, 28] were published as an abstract, and 6 RCTs [8–10, 18, 22, 23] were never published.
Naratriptan 2.5–10 mg was superior to placebo for acute migraine treatment in all 6 RCTs in adults [11, 14, 15, 17, 21, 23], whereas naratriptan 2.5 mg was not superior to placebo in adolescents . In 3 RCTs [11–13], short-term prophylaxis with naratriptan 1 mg b.i.d was superior to placebo for menstruation-associated migraine (MAM). In 2 RCTs [8, 9], naratriptan 2.5 mg was equivalent to naproxen sodium 375 mg for migraine-related quality of life. Naratriptan 2.5 mg (34% preference) was superior to naproxen sodium 500 mg (25% preference) . Naratriptan 2.5 mg [66% headache relief (HR) at 4 h] was inferior to sumatriptan 100 mg (76% HR at 4 h) in one RCT , whereas the higher 10-mg dose of naratriptan (80% HR at 4 h) was quite similar to sumatriptan 100 mg (80% HR at 4 h) .
A recent review on reporting bias in clinical trials  concluded that “the prevalence of incomplete outcome reporting is high”. In addition, when all randomised controlled trials (RCTs) are not published, it results in publication bias, which can be considerable and can distort available evidence .
Publication of well-conducted RCTs is primarily the responsibility of the clinical investigators. However, all the RCTs on naratriptan were multicenter trials (range 10–152 centers) and the pharmaceutical company, GSK was most likely fully in control of both the conduct and the publication of the RCTs. Seven pivotal RCTs [11, 14, 15, 17, 19, 21, 23] were fully published, but one was not  (see Table 1). The reasons for not publishing the 10 other RCT in full remains unknown.
Naratriptan 1 mg b.i.d was superior to placebo for short-term prophylaxis of MAM in 3 RCTs, and naratriptan halved the MAM in one RCT , whereas in 2 RCTs 36% were without MAM versus 27% for placebo [12, 13]; these results suggest a modest effect of short-term prophylaxis with naratriptan in MAM.
Naratriptan was evaluated in 3 RCT versus the NSAID, naproxen sodium [8–10] (see Table 1). In two RCTs, naratriptan was not superior to naproxen sodium 375 mg for migraine-related quality of life [8, 9]. In one RCT, more patients (34%) preferred naratriptan than naproxen sodium 500 mg (25%) . It is unclear why naratriptan 2.5 mg is similar to naproxen 375 mg but better than the higher 500-mg dose of naproxen sodium. It may be due to the design of the studies.
In conclusion, the investigators are obligated to the migraine patients participating in the trials, who often endured placebo administration for 4 h, to ensure that the results of well-conducted, randomised trials are published in peer-reviewed journals. This can be difficult when there are multicenter trials with many investigators, and I suggest that investigators choose a publication committee among themselves, e.g. one from each country or each region.
In this review, all double-blind RCTs with oral naratriptan in the treatment of migraine are presented [8–24]. This does not change the overall picture of an effective and well-tolerated triptan . Whereas naratriptan is superior to placebo, the 2.5-mg dose chosen is less effective than sumatriptan 100 mg (2 and 4 h) (see Table 1), and rizatriptan 10 mg (2 h) . The inferiority of naratriptan versus most other triptans at 2 h has been shown in meta-analyses [1, 2, 4], and this has been ascribed to a slow action of naratriptan . The apparent slow onset of naratriptan 2.5 mg is, however, a matter of dose (see above).
When naratriptan 2.5 mg became an OTC drug, the question of its efficacy compared with other OTC drugs and NSAIDs became relevant. Naratriptan was not compared with paracetamol or aspirin, which in an effervescent form (52% headache relief) was found to have similar efficacy as sumatriptan 50 mg (46% headache relief) in a meta-analysis . There are 2 RCTs comparing naratriptan 2.5 mg with naproxen sodium 275 mg (Table 1). Unfortunately, no placebo-control was used in the RCTs, but no differences between the active drugs were observed. Patients’ preference for naratriptan (34%) was marginally superior to naproxen sodium (26%) (Table 1) in patients dissatisfied with simple analgesics . What is missing is a comparative RCT of naratriptan 2.5 mg (50% headache relief Table 1), and lysine acetylsalicylate and metoclopramide, which showed headache relief of 56% in 2 RCTs [29, 30]. Until such comparative RCTs become available, one cannot, based on the available evidence, recommend what migraine patients should try next when they are dissatisfied with simple analgesics. Naratriptan is a reasonable OTC choice as second or third choice on the step care ladder.
Conflict of interest
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