My 8 week old son has constipation and very bad spit up like throw up. the doctor has him on enfamil ar. i also put karo syrup in bottle.

Wt check, water: Have you tried giving him water? I would recommend starting with 1 oz a day and see if it helps with the constipation. As for the spit ups, if he feeds well, is gaining weight, and does not seem in pain, i would not be treating the reflux symptoms with the above formula. If there are any worsening of his symptoms/problems he should be reevaluated immediately.