What is the dosage for Levofloxacin? The usual dose is 250-750 mg given once daily for 3-14 days depending on the type of infection. Anthrax is treated with 500 mg daily for 60 days. Community-Acquired Pneumonia: 500 mg PO/IV once daily for 7-14 days or 750 mg PO/IV once daily for 5 days. Nosocomial Pneumonia:750 mg PO/IV once daily for 7-14 days. Acute Bacterial Sinusitis: 500 mg PO/IV once daily for 10-14 days or 750 mg PO/IV once daily for 5 days.