In general, it is well tolerated and the side effects are transient at recommended dose. The most frequently reported adverse reaction at the 5-mg dose was constipation (11%), these adverse reactions occur more frequent in patients with slow metabolism. Other common adverse reactions include headache, dizziness, fatigue and GI disorders, eg abdominal pain, diarrhea, etc. Collapse, syncope or cardiovascular arrest has been reported, but the relation with tropisetron HCl has not been established. One or more of the following type I hypersensitivity reactions has been reported: Facial flushing and/or general urticaria, chest tightness, dyspnea, acute bronchospasm and hypotension.