Adult 1-2 g 8 hrly. 
Uncomplicated infection 1 g every 6 or 8 hr. Total daily dosage: 3-4 g. 
Moderately severe or severe infection 2 g every 6 or 8 hr. Total daily dosage: 6-8 g. 
Infections generally needing antibiotics in higher doses 2-3 g every 4 or 6 hr. Total daily dosage: 12 g. 
Renal insufficiency Initially 1-2 g as loading dose. 
Patient undergoing hemodialysis 1-2 g as loading dose after each hemodialysis. 
Mild impairment (CrCl 30-50 mL/min) 1-2 g every 8-12 hr. 
Moderate impairment (CrCl 10-29 mL/min) 1-2 g every 12-24 hr. 
Severe impairment (CrCl 9-5 mL/min) 0.5-1 g every 12-24 hr. 
Essentially no renal function (CrCl <5 mL/min) 0.5-1 g every 24-48 hr. 
Uncomplicated UTI 1 g IM bid. 
Uncomplicated gonorrhea 2 g IM given w/ 1 g of probenecid PO at the same time or up to 1 hr before. 
Neonate, infant & childn 20-40 mg/kg 6-12 hrly, may be increased to 200 mg/kg. Max: 12 g/day. 
Prophylactic use in general surgery Adult 2 g IM or IV ½-1 hr before initial incision, then 2 g 6 hrly. 
Neonate, infant & childn 30-40 mg/kg. 
Caesarean section 2 g IV. 
Prophylaxis in gynecologic surgical procedure 2 g IM or IV 1 to 1½ hr prior to surgery. 
Prolonged or heavily contaminated procedures Additional 2 g at 6 hr interval.