Dosages of Ampicillin/Sulbactam: Adult and Pediatric dosage. Powder for Solution. g (ampicillin 1g/sulbactam g) 3g (ampicillin 2g/sulbactam 1g) 15g (ampicillin 10g/sulbactam 5g) Gynecologic Infections. g (1 g ampicillin/ g sulbactam) to 3 g (2 g ampicillin/1 g sulbactam) via IV or IM every 6 hours; not to exceed 12 g/day.