The safety and tolerability of sumatriptan have been extensively studied. The majority of adverse events (defined as any medical event irrespective of possible causal relationship to treatment) were mild to moderate in intensity, transient and resolved spontaneously. In short-term studies, the most frequently reported adverse events were nausea, vomiting, dizziness, vertigo, malaise, fatigue, injection-site reactions, heaviness, pressure, feelings of warmth and headache. The adverse event profile was unchanged during long-term open treatment and was unaffected by frequency of treatment with sumatriptan. In 3-5% of patients, the symptoms of pressure and warmth were experienced in the chest, but extensive investigations, including ECG monitoring, have indicated that these symptoms are not normally associated with cardiac dysfunction.