More common side effects of seroquel may include abdominal pain, constipation, diminished movement, dizziness, drowsiness, dry mouth, excessive muscle tone, headache, indigestion, low blood pressure (especially upon standing), nasal inflammation, neck rigidity, rapid or irregular heartbeat, rash, sleepiness, tremor, uncontrollable movements, weakness.
Particularly during the first few days of therapy, seroquel can cause low blood pressure, with accompanying dizziness, fainting, and rapid heartbeat.