Have had two other types of antibiotics which didn't clear bronchitis. Also into day three of a five day course of prednisone. The doc told me to take the doxycycline after day three of prednisone if it still hadn't cleared. I took one doxycycline at 4pm ... it is now 8pm and i am experiencing some palpitations... the last couple of hours ... not severe but a bit scary... I'm thinking is from the doxy... is this anything to worry about. ..i have high blood pressure and am on a beta blocker for that and to regulate my heartbeat as i developed an irregular beat due to an adverse side effect from meds years ago. I am going on holiday for a week in the morning. ..should i continue with the doxy... I'm feeling a bit better re cough after only one tablet so i think it may finally clear the broncitis. Any feedback much appreciated