Hello! Thank you for asking on HCM! I read your question and understand your concern! It is important to know that sinus infection can be caused by different types of bacteria, or fungal infections which react differently to a certain antibiotic. Usually the situation begins to get better in a couple of days from the begin of the antibiotic, though it should be continued for 10days. If the fever persists I recommend performing a sinus discharge culture and antibiogram to find the proper therapy effective against the causative agent. Hope to have been helpful! Greetings! Dr. Aida