If you are an adult 500mg of Azithromycin
. If it is a mild sinusitis
I think you can go ahead but if it is severe better go for Amoxycillin-clavulanic acid
combination. Also, you can take mucolytics, saline nasal drops and anti-inflammatory drugs if you have headache. But the best treatment is steam inhalation and drinking plenty of warm water.
Any more doubts you are welcome.
Dr. Naveen Kumar