Benicar (Olmesartan) warnings. Benicar contains a black-box warning because it can cause death or serious injury to an unborn baby when taken during the last six months of pregnancy. You shouldn’t take this medicine if you’re pregnant or plan to become pregnant. Symptoms may include:

  • severe diarrhea
  • significant weight loss
  • stomach pain and discomfort

This medicine may also cause dizziness or fainting when you get up too quickly from a lying position. Tell your doctor if this symptom becomes severe.