311C90 (Zomig; zolmitriptan) is a novel, selective serotonin (5HT)1B/1D receptor 
agonist with both central and peripheral activity, now in late-stage clinical 
development for acute oral treatment of migraine. Several studies have 
demonstrated the tolerability and efficacy of 311C90 in the treatment of a 
single migraine headache. The objectives of this open-label study were to assess 
the tolerability and efficacy of repeated doses of 5 mg of 311C90 for acute 
treatment of multiple attacks for up to 1 year. Patients were allowed to treat 
as many migraine headaches (mild, moderate, or severe) as desired with an 
initial dose. A second 5-mg dose could be used to treat recurrence should it 
develop. Safety assessments included ECG, the frequency, intensity, and duration 
of adverse experiences, and routine hematology, urinalysis, and clinical 
chemistry parameters. Efficacy assessments included headache severity at 2 hours 
(i.e., severe, moderate, mild, or none), the proportion of patients pain-free at 
2 hours, the use of a second tablet to treat headache recurrence if it 
developed, and the consistency of these findings over time. The efficacy profile 
and the nature/incidence of adverse events reported appear to be consistent with 
previous 311C90 studies. The dosing regimen was well tolerated during multiple 
exposures. Notably, headache response rates were consistently good after both 
initial and repeated exposure (> 80% across 1 to 30 attacks). For 67% of 
patients who treated at least five attacks, 311C90 was effective 80 to 100% of 
the time.