Does Loestrin Reduce The Effectiveness Of Contraceptive Pills?

I m on Loestrin 20 and have been given a three day course for a suspected re orccuring Urine track infection. When I start them I will also be taking my pill, but when the round is finished my seven day break/period is due the next day. I will not be sexually active till I start the next back after seven days, will I need to make any further precautions?