Treatment of Postpartum Pyelonephritis Ceftriaxone alone or ampicillin plus gentamicin Initial treatment of pyelonephritis is ceftriaxone 1 to 2 g IV every 12 to 24 hours alone or ampicillin 1 g IV every 6 hours plus gentamicin 1.5 mg / kg IV every 8 hours until women are afebrile for 48 hours.