One dose of preoperative intravenous (iv) antibiotic (e.g., cefazolin 1gm, or cefuroxime 1.5gm, or clindamycin 300mg will be administered within 60 minutes of start of surgery. Repeat intraoperative dosing of antibiotics is permitted if length of surgery exceeds recommended dosing interval. IV antibiotic dosing schedules: Cefazolin 1 gm iv Q6 hr -or- Cefuroxime 1.5gm iv Q8 hr -or- Clindamycin 300 mg iv Q12 hr. Postoperative antibiotics: Study participants will receive one dose only of postoperative intravenous antibiotic (e.g., cefazolin 1gm, or cefuroxime 1.5gm, or clindamycin 300mg [cephalosporin allergic patients]) according to the recommended dosing schedule described above. This dose of antibiotics is in addition to the preoperative dose. Placebo PO BID (twice daily) will commence on the morning of postoperative day 1 and continue for 7 days.

One dose of preoperative iv antibiotic (cefazolin 1gm, or cefuroxime 1.5gm, or clindamycin 300mg) will be administered within 60 minutes of start of surgery. Repeat intraoperative dosing of antibiotics is permitted if length of surgery exceeds recommended dosing interval. IV antibiotic dosing schedules: Cefazolin 1 gm iv Q6 hr -or- Cefuroxime 1.5gm iv Q8 hr -or- Clindamycin 300 mg iv Q12 hr. Participants will receive 1 dose only of postoperative iv antibiotic (cefazolin 1gm, or cefuroxime 1.5gm, or clindamycin 300mg [cephalosporin allergic patients]) according to the recommended dosing schedule described above. This dose of antibiotics is in addition to the preoperative dose. Oral antibiotics will commence on the morning of postoperative day 1; this group will receive oral antibiotics (cefdinir [Omnicef®] 300 mg PO BID or trimethoprim/sulfamethoxazole [Bactrim DS™] PO BID for cephalosporin intolerant patients) for 7 days.

PO BID placebo for 7 days. Postoperative days 1 through 7: patients will administer saline spray (e.g., Ocean nasal spray) to both nostrils four times daily. Postoperative days 8 through 30: patients will begin twice daily sinus irrigation rinse (e.g., Neti-pot) until day 30. After day 30, patients will perform sinus irrigation as needed. If a patient is unable to tolerate nasal rinses, saline spray can be used as an alternative.

Completed by subject in clinic or by phone interview. Assesses urge to blow nose; post-nasal discharge; thick nasal discharge; headaches; nose makes whistling sound; nasal crusting; trouble breathing through nose during day; trouble breathing through nose during night; not breathing equally in both nostrils; sense of smell; sense of taste; and, overall functioning of nose.Rating choices include no problem 0; very minor problem 1; minor problem 2; moderate problem 3; moderately severe problem 4; and, severe problem 5. Subject also selects the 5 symptoms/items listed that impact life the most.

Completed by subject in clinic or by phone interview. Assesses need to blow nose; nasal blockage; sneezing; runny nose; cough; post-nasal discharge; thick nasal discharge; ear fullness; dizziness; ear pain; facial pain/pressure; decreased sense of smell/taste; difficulty falling asleep; waking up at night; lack of a good night's sleep; wake up tired; fatigue; reduced productivity; reduced concentration; frustrated/restless/irritable; sad; and, embarrassed. Rating choices include no problem 0; very mild problem 1; mild or slight problem 2; moderate problem 3; severe problem 4; problem as bad as it can be 5. Subject also selects the 5 symptoms/items listed that impact life the most.

Incidence includes 3 or more of: i. Nasal congestion by patient report or physical exam, ii. Purulent nasal discharge by patient report or physical exam, iii. Facial pressure or pain or headache by patient report, iv. Antibiotics prescribed by a provider for the purpose of treating sinusitis.