<s>[INST] My doctor just put me on the generic form of Ritalin to help with the vegetative symptoms of major depression I have had.  I only take half of a 10mg pill, and I have had very painful stomach cramping, feeling like a bad case of diarrhea.  What should I do? [/INST] Degree understand your concerns went through your details. I suggest you not to worry much. Ritalin (methylphenidate) is a central nervous system stimulant. It affects chemicals in the brain and nerves that contribute to hyperactivity and impulse control. Stomach pain, nausea, vomiting, upset stomach are side effects associated with this Chat Doctor.  Please consult your psychiatrist for further advice. Please post a direct question to me in this website. Make sure that you include every minute details possible. I shall prescribe some psychotherapy techniques which should help you cure your condition. Hope this answers your query. Available for further clarifications. Good luck. </s>