<prompt> Which of the following is the most common adverse effect of omeprazoleNauseaConstipationJaundiceBlack stools  <response>: PROTON PUMP INHIBITORS PPIs Omeprazole Adverse effects:- Nausea, loose stools, headache, abdominal pain, muscle and joint pain, dizziness, Rashes. Leucopenia and hepatic dysfunction are infrequent. On prolonged treatment atrophic gastritis has been repoed. Ref:- kd tripathi; pg num:- 653 