Early congenital syphilis In confirmed or highly probable cases, the 2021 Centers for Disease Control and Prevention (CDC) STI treatment guidelines recommend aqueous crystalline penicillin G 50, 000 units / kg IV every 12 hours for the first 7 days of life and every 8 hours thereafter for a total of 10 days or procaine penicillin G 50, 000 units / kg IM once / day for 10 days (see Table: Recommended Dosages of Selected Parenteral Antibiotics for Neonates).