Common side effects of Risperdal: 1  A Feeling of Restlessness with Inability to Sit Still Severe. 2  Acute Infection of the Nose, Throat or Sinus Severe. 3  Extrapyramidal Reaction Severe. 4  Parkinson Symptoms Severe. 5  Problems with Eyesight Severe. 6  Voluntary Movement Difficulty Severe.