CNS Effects of Sumatriptan and Rizatriptan

Dear sir In their recent article, van der Post et al. (1) reported results from a study in which rizatriptan 10 mg and sumatriptan 100 mg were found to have minimal CNS effects, compared with temazepam 20 mg, on a battery of psychometric tests administered to 17 healthy women. Rizatriptan produced slightly greater impairment than sumatriptan, and the authors suggested that rizatriptan effects may have been underestimated because of encapsulation. The clinical relevance of these small differences between rizatriptan and sumatriptan in healthy women is unclear. To investigate this issue, we retrospectively analysed adverse event data from a large randomized, double-blind, placebo-controlled study which directly compared rizatriptan 10 mg with sumatriptan 100 mg for the treatment of a migraine attack (2). Supplies of rizatriptan and sumatriptan were not encapsulated. We looked at the percentages of migraine patients with any CNS adverse event, or with specific CNS adverse events of dizziness and drowsiness (the 2 most common CNS adverse events following triptan use). The results are shown in Table 1. There was no evidence that rizatriptan resulted in more CNS adverse events than sumatriptan. In fact, a slightly higher percentage of patients taking sumatriptan reported any CNS adverse event compared with patients taking rizatriptan. Both rizatriptan and sumatriptan were associated with an increase in CNS adverse events compared with placebo, but most events were of mild or moderate severity and were short-lasting. A study which directly compared rizatriptan 10 mg with the lower, 50-mg, dose of sumatriptan also found similar percentages of patients with CNS adverse events in the active treatment groups (3). These results suggest that, clinically, rizatriptan and sumatriptan have similar CNS effects.

Table 1

CNS adverse events following sumatriptan, rizatriptan, or placebo

No. of patients with (%)	Sumatriptan 100 mg (n = 388)	Rizatriptan 10 mg (n = 387)	Placebo (n = 160)
Any CNS adverse event	29.6∗ †	22.5†	15.0
Dizziness	9.0†	7.8	3.8
Drowsiness	7.2	8.5	5.6
Any drug-related‡ CNS adverse event	22.9∗ †	16.5†	8.8
Drug-related‡ dizziness	6.7	5.9	2.5
Drug-related‡ drowsiness	5.9	6.7	3.1

∗Significantly higher than rizatriptan (P < 0.05, Fisher's Exact test).

†Significantly higher than placebo (P < 0.05, Fisher's Exact test).

‡Adverse events rated as possibly, probably or definitely drug-related by the investigator.