You should not use Ritalin if you have glaucoma, tics or Tourette’s syndrome, or severe anxiety, tension, or agitation. Methylphenidate may be habit-forming, and this medicine is a drug of abuse. Tell your doctor if you have had problems with drug or alcohol abuse. Stimulants have caused stroke, heart attack, and sudden death in people with high blood pressure, heart disease, or a heart defect. Do not use Ritalin if you have used an MAO inhibitor in the past 14 days, such as isocarboxazid, linezolid, methylene blue injection, phenelzine, rasagiline, selegiline, or tranylcypromine. Methylphenidate may cause new or worsening psychosis (unusual thoughts or behavior), especially if you have a history of depression, mental illness, or bipolar disorder.