Tri-lo-sprintec is an estrogen and progestin which works by preventing ovulation and therefore preventing pregnancy. You should not use Tri-lo-Sprintec if you are allergic to any ingredient in it or if you have chest pain caused by angina or if you have an abnormal vaginal bleeding. Tri-Lo-Sprintec should not be used in children who have not had their first menstrual period. Tri-Lo-Sprintec is a contraceptive used for birth control purposes. It is packed with female hormones, which block ovulation from happening.